AIRHEAD MEG CABOT

Tìm thấy 14 tài liệu liên quan tới từ khóa "AIRHEAD MEG CABOT":

MIA THERMOPOLIS (MEG CABOT) RANSOM MY HEART

MIA THERMOPOLIS (MEG CABOT) RANSOM MY HEART

Nhật ký công chúa bổ sung. Ở tập này công chúa của chúng ta vẫn sẽ kể về hoạt động, tâm trạng, cảm xúc hàng ngày nhưng từ ngữ ở mức độ cao hơn. Vì thế sẽ nâng cao trình độ đọc hiểu của độc giả, người học.

273 Đọc thêm

MEG CABOT THE PRINCESS DIARIES 07 PARTY PRINCESS

MEG CABOT THE PRINCESS DIARIES 07 PARTY PRINCESS

FTLOUIE: Michael, I can’t go to your party because I don’t even like parties and besides I think it’s going to be totally boring hanging out with a bunch of college people, especially if[r]

218 Đọc thêm

MEG CABOT THE PRINCESS DIARIES 09 PRINCESS MIA

MEG CABOT THE PRINCESS DIARIES 09 PRINCESS MIA

Nhật ký công chúa tập 9 phần tiếp theo của tập 1. Đọc đến đây chắc chắc bạn đã là fan thân yêu của công chúa mia rồi. Vì thế hãy cùng trải nghiệm và tiếp tục cuộc hành trình tìm hiểu về cuộc sống, công việc của princess mia nhé

300 Đọc thêm

MEG CABOT THE PRINCESS DIARIES 03 PRINCESS IN LOVE

MEG CABOT THE PRINCESS DIARIES 03 PRINCESS IN LOVE

when are you going to tell Michael that you're the one who sent him those cards?' Shocked, I went, 'How about never?' To which Tina replied, tartly, 'Mia, if you don't tell him, then wha[r]

127 Đọc thêm

MEG CABOT THE PRINCESS DIARIES 041 PRINCESS IN WAITING

MEG CABOT THE PRINCESS DIARIES 041 PRINCESS IN WAITING

But I think the contessa maybe went a little far with the surgery thing - it is so hard to know when to say 'when', I mean, look at poor Michael Jackson - because she really does, just l[r]

127 Đọc thêm

MEG CABOT THE PRINCESS DIARIES 06 PRINCESS IN TRAINING

MEG CABOT THE PRINCESS DIARIES 06 PRINCESS IN TRAINING

Because, of course, it totally descended into a game of the Popular versus the Unpopular, with Lana picking Trisha and all of her heinous friends, and me picking Lilly and all of the unc[r]

179 Đọc thêm

MEG CABOT THE PRINCESS DIARIES 04 2 AND A HALF PROJECT PRINCESS

MEG CABOT THE PRINCESS DIARIES 04 2 AND A HALF PROJECT PRINCESS

I thought Michael was talking about theMothman , you know, from that movie, and I couldn’t think what was so great about that because all theMothman does is call people on the phone and [r]

23 Đọc thêm

Ảnh thông báo ''''tin vui'''' hút nghìn ''''like'''' của cặp đồng tính nữ

ẢNH THÔNG BÁO ''''TIN VUI'''' HÚT NGHÌN ''''LIKE'''' CỦA CẶP ĐỒNG TÍNH NỮ

window.onload = function () {resizeNewsImage("news-image", 500);} Với sự phổ biến của mạng xã hội như facebook, các cặp đôi có nhiều cách hài hước và độc đáo hơn để thông báo họ sắp có con, thay vì cách truyền thống là gửi bưu thiếp như trước đây. Có em bé luôn là một tin vui bất ngờ với các cặp vợ chồng và sẽ càng đặc biệt hơn với cặp vợ chồng đồng tính nữ Meg và Becca. Cuối tuần trước, Meg Owen tung lên Reddit một bức ảnh với lời đề tựa: "Một đứa trẻ đặc biệt sẽ được chào đời trong một gia đình đặc biệt.” Trong bức ảnh là nụ cười vô vàn hạnh phúc, bất ngờ của Meg và vợ Becca, cả hai cùng mặc áo phông trắng khi chia sẻ tin vui của họ. Trên áo của Recca có dòng chữ: “Tôi đang mang bầu” và bên cạnh đó là khuôn mặt kinh ngạc của Meg với dòng chữ trên áo: “Tôi không phải là cha của đứa trẻ”. Trong nụ cười rạng rỡ của những người được làm cha làm mẹ, họ chia sẻ: “Chúng tôi cảm thấy vô cùng may mắn và hạnh phúc khi có người thân và bạn bè luôn bên cạnh, ủng hộ và giúp đỡ để chúng tôi đến được với nhau và ngày hôm nay tình yêu của chúng tôi đã nở hoa kết trái”.   Bức ảnh thông báo tin vui có bầu của cặp đồng tính nữ. Sau khi được đăng tải lên Reddit, bức ảnh ghi lại cảnh cặp đôi đồng tính hạnh phúc thông báo “tin vui” đã thu hút hàng nghìn lượt "like" và chia sẻ của cư dân mạng. Trước tình cảm mà mọi người dành cho gia đình mình, Meg và Becca đã lên tiếng cho biết những bức ảnh chứng minh cho tình yêu vô điều kiện cũng như niềm tự hào của họ. “Chúng tôi cũng muốn thông báo tin vui này theo một cách đặc biệt nhất tới tất cả những người yêu quý và ủng hộ chúng tôi, rằng gia đình chúng tôi sẽ chào đón thành viên mới”, Meg nói. Becca có bầu thành công thông qua phương pháp bơm tinh trùng vào buồng trứng, và cô dự định sẽ sinh vào tháng 7 tới. Meg chia sẻ thêm: “Những người thân và bạn bè của chúng tôi cũng vô cùng bất ngờ khi biết được tin này. Đã có những giọt nước mắt, những nụ hôn của sự vui mừng, hạnh phúc. Đứa trẻ chào đời sẽ có tới hai người mẹ tuyệt vời”. Mặc dù sau khi đăng tải trên Reddit, tin tức này đã nhanh chóng bị “vùi lấp” trong các "post" khác, họ vẫn nhận được rất nhiều tin nhắn chúc mừng, chia vui từ những người thậm chí họ không quen biết. Tin vui của cặp vợ chồng đồng tính thắp lên hi vọng cho các cặp đôi đồng tính khác, tuy nhiên cũng gây nên những tranh luận nhiều chiều về tình yêu, hạnh phúc, về sự công bằng mà những cặp đôi đồng tính xứng đáng được hưởng. Cuối cùng vợ chồng Owen và Becca hi vọng với chia sẻ đầy “hóm hỉnh” của mình, họ mong mọi người hãy yêu thương và chia sẻ với họ, với đứa con sẽ chào đời của họ như bao cặp đôi bình thường khác mà không phân biệt họ là những người đồng tính. Meg cũng hi vọng khi mọi người nhìn thấy bức ảnh này, họ sẽ cảm nhận được tình yêu thực sự, một tình yêu vượt lên trên tất cả những quan niệm truyền thống. Thiên thần nhỏ chào đời vào tháng 7 tới sẽ là minh chứng cho điều đó.
Xem thêm

1 Đọc thêm

GRAMMAR SPACE 2 UNIT TEST 07

GRAMMAR SPACE 2 UNIT TEST 07

A. Choose the correct answers.1. Mr. and Mrs. Jones _____________ to visit Turkey this fall.planingare planingare planning2. Sam and his friend _____________ spaghetti now.aren’taren’t eatingaren’t eatting3. The boy is _____________ oranges in front of the people.jugglejugglingjuggleing4. Is Meg _____________ up the balloons for the party?blowsblowwingblowingB. Choose and complete the sentences in the present continuous.circlenot studyrelaxnot writelisten1. The toy airplanes _________________________________ in the sky.2. I _________________________________ science these days.

2 Đọc thêm

Ảnh bầu ''''ngọt lịm'''' của các cặp đôi đồng tính nữ

ẢNH BẦU ''''NGỌT LỊM'''' CỦA CÁC CẶP ĐÔI ĐỒNG TÍNH NỮ

window.onload = function () {resizeNewsImage("news-image", 500);} Ngày 26/6 vừa qua và những năm tiếp theo sẽ là một ngày quan trọng với cộng đồng LGBT (viết tắt từ: Lesbian (đồng tính nữ), Gay (đồng tính nam), Bisexual (song tính nam hoặc nữ), Transsexual/Transgender (hoán tính/chuyển giới)) ở Mỹ nói riêng và trên toàn thế giới. Cộng đồng LGBT ở nước này vô cùng hân hoan trước quyết định của Tòa án tối cao công nhận quyền hợp pháp của kết hôn đồng giới. Kể từ nay, mọi người dân trên toàn nước Mỹ đều có quyền tự do bình đẳng yêu thương và kết hôn, không phân biệt giới tính.  Những cặp đồng tính nam và nữ có thể đăng ký kết hôn và được luật hôn nhân bảo vệ các vấn đề liên quan như con cái, tài sản sau khi ly hôn.   Từ ngày 26/6, tòa án Mỹ đã chính thức công nhận quyền hợp pháp của kết hôn đồng giới. Trên thực tế thì mặc dù trước đây, luật pháp nước này chưa từng cho phép hôn nhân đồng giới nhưng rất nhiều cặp đôi đã đi theo tiếng gọi tình yêu và đến với nhau. Không chỉ chung sống một nhà, họ còn lên kế hoạch thay nhau mang thai, sinh con và sinh sống như bao gia đình bình thường khác. Tình yêu, cuộc sống gia đình của họ đã nhận được sự đồng cảm cũng như ủng hộ của hầu hết mọi người trên toàn thế giới. Và chắc chắn sau sự kiện được tòa án công nhận quyền hợp pháp của kết hôn đồng giới, họ sẽ còn vui mừng hơn gấp bội. Cùng ngắm lại những bộ ảnh bầu bí, sinh nở tuyệt đẹp của các cặp đôi đồng tính nữ:   Cặp đôi Melanie và Vanessa Iris Roy (Bắc Carolina, Mỹ) đã chụp những bức ảnh vô cùng ý nghĩa về những lần mang thai của mình.   Những bức ảnh thay nhau mang thai của cặp đôi đồng tính nữ.   Bức ảnh mang thai của cặp đôi Maryellen Olson và Heidi. Họ kết hôn năm 2012 và đã quyết định sinh con ngay sau đó.   Tuy nhiên Heidi đã mất một thời gian dài chiến đấu với bệnh lạc nội mạc tử cung trước khi có bầu.   Điều đáng nói là trong thời gian Heidi mang bầu, Maryellen Olson cũng sử dụng một loại hormone để kích thích tuyến sữa. Và khi em bé chào đời, cả hai đều có thể cho con bú.   Cặp đôi cho biết, sự có mặt của em bé đã thay đổi hoàn toàn cuộc sống của họ.   Bộ ảnh bầu bí vô cùng ngọt ngào của cặp đôi đồng tính nữ Amy và Alexis Vaughn.   Họ đã có thời gian hơn 1,5 năm quen biết, yêu và đính hôn trước khi có con.   Bức ảnh thông báo tin vui của cặp đồng tính nữ Meg và Becca đã hút nghìn 'like' từ cộng đồng mạng.   Còn đây là bộ ảnh sinh nở của cặp đôi Stephanie và Desiree Bryan.   Họ kết hôn từ năm 2010 nhưng mãi đến năm 2014 mới thụ thai thành công.   Điều may mắn là Desiree Bryan đã thụ thai đôi từ trứng của Stephanie và tinh trùng hiến tặng.   Cặp đôi hạnh phúc bên cặp song sinh của mình.
Xem thêm

2 Đọc thêm

Phương pháp chẩn đoán hình ảnh medical image analysis methods (phần 11)

PHƯƠNG PHÁP CHẨN ĐOÁN HÌNH ẢNH MEDICAL IMAGE ANALYSIS METHODS (PHẦN 11)

11 Estimation of Human Cortical Connectivity with Multimodal Integration of fMRI and HighResolution EEG Laura Astolfi, Febo Cincotti, Donatella Mattia, Serenella Salinari, and Fabio Babiloni CONTENTS 11.1 Introduction 11.2 Methods 11.2.1 Monitoring the Cerebral Hemodynamic Response by fMRI 11.2.2 Structural Equation Modeling 11.2.3 Directed Transfer Function 11.2.4 Computer Simulation 11.2.4.1 The Simulation Study 11.2.4.2 Signal Generation for the SEM Methodology 11.2.4.3 Signal Generation for the DTF Methodology 11.2.4.4 Performance Evaluation 11.2.4.5 Statistical Analysis 11.2.5 Application to MovementRelated Potentials 11.2.5.1 Subject and Experimental Design 11.2.5.2 Head and Cortical Models 11.2.5.3 EEG Recordings 11.2.5.4 Statistical Evaluation of Connectivity Measurements by SEM and DTF 11.2.5.5 Estimation of Cortical Source Current Density 11.2.5.6 Regions of Interest (ROIs) 11.2.5.7 Cortical Current Waveforms 11.3 Results 11.3.1 Computer Simulations for SEM 11.3.2 Computer Simulations for DTF Copyright 2005 by Taylor Francis Group, LLC 396 Medical Image Analysis 11.3.3 Application to HighResolution EventRelated Potential Recordings 11.3.4 Application of the Multimodal EEGfMRI Integration Techniques to the Estimation of Sources of SelfPaced Movements 11.4 Discussion 11.4.1 Simulation Results for SEM 11.4.2 Simulation Results for DTF 11.4.3 Application of Connectivity Estimation Methods to Real EEG Data 11.4.4 Application of Connectivity Estimation Methods to Real EEG Data 11.5 Conclusions Acknowledgment References 11.1 INTRODUCTION Human neocortical processes involve temporal and spatial scales spanning several orders of magnitude, from the rapidly shifting somatosensory processes characterized by a temporal scale of milliseconds and a spatial scale of a few square millimeters to the memory processes, involving time periods of seconds and a spatial scale of square centimeters. Information about the brain activity can be obtained by measuring different physical variables arising from the brain processes, such as the increase in consumption of oxygen by the neural tissues or a variation of the electric potential over the scalp surface. All these variables are connected in direct or indirect way to the ongoing neural processes, and each variable has its own spatial and temporal resolution. The different neuroimaging techniques are then confined to the spatiotemporal resolution offered by the monitored variables. For instance, it is known from physiology that the temporal resolution of the hemodynamic deoxyhemoglobin increasedecrease lies in the range of 1 to 2 sec, while its spatial resolution is generally observable with the current imaging techniques at the scale of a few millimeters. Today, no neuroimaging method allows a spatial resolution on a millimeter scale and a temporal resolution on a millisecond scale. Hence, it is of interest to study the possibility of integrating the information offered by the different physiological variables in a unique mathematical context. This operation is called the “multimodal integration” of variable X and Y, where the X variable typically has a particularly appealing spatial resolution property (millimeter scale), and the Y variable has particularly attractive temporal properties (on a millisecond scale). Nevertheless, the issue of several temporal and spatial domains is critical in the study of the brain functions, because different properties could become observable, depending on the spatiotemporal scales at which the brain processes are measured. Electroencephalography (EEG) and magnetoencephalography (MEG) are two interesting techniques that present a high temporal resolution, on the millisecond scale, adequate to follow brain activity. However, both techniques have a relatively Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 397 modest spatial resolution, beyond the centimeter. Spatial resolution for these techniques is fundamentally limited by the intersensor distances and by the fundamental laws of electromagnetism 1. On the other hand, the use of a priori information from other neuroimaging techniques like functional magnetic resonance imaging (fMRI) with high spatial resolution could improve the localization of sources from EEGMEG data. The initial part of this chapter then deals with the multimodal integration of electrical, magnetic, and hemodynamic data to locate neural sources responsible for the recorded EEGMEG activity. The rationale of the multimodal approach based on fMRI, MEG, and EEG data to locate brain activity is that neural activity generating EEG potentials or MEG fields increases glucose and oxygen demands 2. This results in an increase in the local hemodynamic response that can be measured by fMRI 3, 4. On the whole, such a correlation between electrical and hemodynamic concomitants provides the basis for a spatial correspondence between fMRI responses and EEGMEG source activity. However, static images of brain regions activated during particular tasks do not convey the information of how these regions communicate with each other. The concept of brain connectivity is viewed as central for the understanding of the organized behavior of cortical regions beyond the simple mapping of their activity 5, 6. This organization is thought to be based on the interaction between different and differently specialized cortical sites. Corticalconnectivity estimation aims at describing these interactions as connectivity patterns that hold the direction and strength of the information flow between cortical areas. To achieve this, several methods have already been applied on data gathered from both hemodynamic and electromagnetic techniques 7–11. Two main definitions of brain connectivity have been proposed over the years: functional and effective connectivity 12. While functional connectivity is defined as temporal correlation between spatially remote neurophysiologic events, the effective connectivity is defined as the simplest brain circuit that would produce the same temporal relationship as observed experimentally between cortical sites. As for the functional connectivity, the several computational methods proposed to estimate how different brain areas are working together typically involve the estimation of some covariance properties between the different time series measured from the different spatial sites during motor and cognitive tasks studied by EEG and fMRI techniques 13–16. In contrast, structural equation modeling (SEM) is a different technique that has been used for a decade to assess effective connectivity between cortical areas in humans by using hemodynamic and metabolic measurements 7, 17–19. The basic idea of SEM differs from the usual statistical approach of modeling individual observations, because SEM considers the covariance structure of the data 17. However, the estimation of cortical effective connectivity obtained with the application of the SEM technique on fMRI data has a low temporal resolution (on the order of 10 sec), which is far from the time scale at which the brain operates normally. Hence, it becomes of interest to understand whether the SEM technique could be applied to cortical activity estimated by applying the linearinverse techniques to the highresolution EEG (HREEG) data 20–23. In this way, it would be possible to study timevarying patterns of brain connectivity linked to the different parts of the experimental task studied. Copyright 2005 by Taylor Francis Group, LLC 398 Medical Image Analysis So far, the estimation of functional connectivity on EEG signals has been addressed by applying either linear or nonlinear methods, both of which can track the direct flow of information between scalp electrodes in the time domain, although with different computational demands 21, 24–31. In addition, given the evidence that important information in the EEG signals is often coded in the frequency rather than time domain (reviewed in 32), research attention has been focused on detecting frequencyspecific interactions in EEG or MEG signals by analyzing the coherence between the activity of pairs of structures 33–35. However, coherence analysis does not have a directional nature (i.e., it just examines whether a link exists between two neural structures by describing instances when they are in synchronous activity), and it does not directly provide the direction of the information flow. In this respect, a multivariate spectral technique called directed transfer function (DTF) was proposed 36 to determine the directional influences between any given pair of channels in a multivariate data set. This estimator can simultaneously characterize both the directional and spectral properties of the brain signals, requiring only one multivariate autoregressive (MVAR) model that is estimated from all of the EEG channel recordings. The DTF technique has recently been demonstrated 37 to rely on the key concept of Granger causality between time series 38, according to which an observed time series x(n) generates another series y(n) if knowledge of x(n)’s past significantly improves the prediction of y(n). This relation between time series is not reciprocal, i.e., x(n) may cause y(n) without y(n) necessarily causing x(n). This lack of reciprocity is what allows the evaluation of the direction of information flow between structures. In this study, we propose to estimate the patterns of cortical connectivity by exploiting the SEM and DTF techniques applied on highresolution EEG signals, which exhibit a higher spatial resolution than conventional cerebral electromagnetic measures. Indeed, this EEG technique includes the use of a large number of scalp electrodes, realistic models of the head derived from structural magnetic resonance images (MRIs), and advanced processing methodologies related to the solution of the linearinverse problem. These methodologies facilitate the estimation of cortical current density from sensor measurements 39–41. To pursue the aim of this study, we first explored the behavior of the SEM and DTF methods in a simulation context under various conditions that affect the EEG recordings, mainly the signaltonoise ratio (factor SNR) and the length of the recordings (factor LENGTH). In particular, the following questions were addressed: What is the influence of a variable SNR level (imposed on the highresolution EEG data) on the accuracy of the estimation of pattern connectivity obtained by SEM and DTF? What amount of highresolution EEG data is needed to accurately estimate the accuracy of the connectivity between cortical areas? To answer these questions, a simulation study was performed on the basis of a predefined connectivity scheme that linked several modeled cortical areas. Cortical connections between these areas were retrieved by the estimation process under different experimental SNR and LENGTH conditions. Indexes of the errors in the estimation of the connection strength were defined, and statistical multivariate analyses Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 399 were performed by ANOVA (analysis of variance) and Duncan post hoc tests, with these error indexes as dependent variables. Subsequently, both SEM and DTF methods were applied to the cortical estimates obtained from highresolution EEG data related to a simple fingertapping experiment in humans to underline the capability of the proposed methodology to draw patterns of cortical connectivity between brain areas during a simple motor task. Finally, we also present both the mathematical principle and the practical applications of the multimodal integration of highresolution EEG and fMRI for the localization of sources responsible for intentional movements. 11.2 METHODS 11.2.1 MONITORING THECEREBRALHEMODYNAMICRESPONSE BY FMRI A brainimaging method, known as functional magnetic resonance imaging (fMRI), has gained favor among neuroscientists over the last few years. Functional MRI reflects oxygen consumption, and because oxygen consumption is tied to processing or neural activation, it can give a map of functional activity. When neurons fire, they consume oxygen, and this causes the local oxygen levels to decrease briefly and then actually increase above the resting level as nearby capillaries dilate to let more oxygenated blood flow into the active area. The most commonly used acquisition paradigm is the socalled bloodoxygen level dependence (BOLD), in which the fMRI scanner works by imaging blood oxygenation. The BOLD paradigm relies on the brain mechanisms, which overcompensate for oxygen usage (activation causes an influx of oxygenated blood in excess of that used, and therefore the local oxyhemoglobin concentration increases). Oxygen is carried to the brain in the hemoglobin molecules of blood red cells. Figure 11.1shows the physiologic principle at the base of the generation of fMRI signals. This figure shows how the hemodynamic responses elicited by increased neuronal activity (Figure 11.1(a)) reduce the deoxyhemoglobin content of the blood flow in the same neuronal district after a few seconds (Figure 11.1(b)).The magnetic properties of hemoglobin when saturated with oxygen are different than when it has given up oxygen. Technically, deoxygenated hemoglobin is paramagnetic and therefore has a short relaxation time. As the ratio of oxygenated to deoxygenated hemoglobin increases, so does the signal recorded by the MRI. Deoxyhemoglobin increases the rate of depolarization of the hydrogen nuclei creating the MR signal, thus decreasing the intensity of the T2 image. The bottom line is that image intensity increases with increasing brain activation. The problem is that at the standard intensity used for the static magnetic field (1.5 Tesla), this increase is small (usually less than 2%) and easily obscured by noise and various artifacts. By increasing the static field of the fMRI scanner, the signaltonoise ratio increases to more convenient values. Staticfield values of 3 Tesla are now commonly used for research on humans, while an fMRI scanner at 7 Tesla was recently employed to map hemodynamic responses in the human brain 42. At such a high field value, there is a possibility of detecting the initial increase of deoxyhemoglobin (after the initial “dip”). The interest in the detection of the dip is based on the fact that this hemodynamic response happens on a time scale of 500 msec (as revealed by hemodynamic optical Copyright 2005 by Taylor Francis Group, LLC 400 Medical Image Analysis measures 43) compared with 1 to 2 sec needed for the response of the vascular system to the oxygen demand. Furthermore, in the latter case, the response has a temporal extension well beyond the activation that has occurred (10 sec). As a last point, the spatial distribution of the initial dip (as described by using the optical dyes 43) is sharper than those related to the vascular response of the oxygenated hemoglobin. Recently, with highfieldstrength MR scanners at 7 or even 9.4 Tesla (on animals), a resolution down to the corticalcolumn level has been achieved 44. However, at the standard field intensity commonly used in fMRI studies (1.5 or 3 Tesla), the identification of such initial transient increase of deoxyhemoglobin is controversial. Compared with positronemitted tomography (PET) or singlephotonemitted tomography (SPECT), fMRI does not require the injection of radiolabeled substances, and its images have a higher resolution (as reviewed in the literature 45). PET, however, is still the most informative technique for directly imaging metabolic processes and neurotransmitter turnover. 11.2.2 STRUCTURALEQUATIONMODELING In structural equation modeling (SEM), the parameters are estimated by minimizing the difference between the observed covariances and those implied by a structural or path model. In terms of neural systems, a measure of covariance represents the degree to which the activities of two or more regions are related. FIGURE 11.1 (Color figure follows p. 274.)Physiologic principle at the base of the generation of fMRI signals. (a) Neurons increase their firing rates, which increases oxygen consumption. (b) Hemodynamic response in a second scale increases the diameter of the vessel close to the activated neurons. The induced increase in blood flow overcomes the need for oxygen supply. As a consequence, the percentage of deoxyhemoglobin in the blood flow decreases in the vessel with respect to (a). Hemoglobin Oxygen (a) (b) fMRI Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 401 The SEM consists of a set of linear structural equations containing observed variables and parameters defining causal relationships among the variables. Variables in the equation system can be endogenous (i.e., dependent on the other variables in the model) or exogenous (independent of the model itself). The structural equation model specifies the causal relationship among the variables, describes the causal effects, and assigns the explained and the unexplained variance. Let us consider a set of variables (expressed as deviations from their means) with N observations. In this study, these variables represent the activity estimated in each cortical region, obtained with the procedures described in the following section. The SEM for these variables is the following: y = By + Γx + ζ (11.1) where: y is a (m × 1) vector of dependent (endogenous) variables x is a (n × 1) vector of independent (exogenous) variables ζ is a (m × 1) vector of equation errors (random disturbances) B is a (m × m) matrix of coefficients of the endogenous variables Γ is a (m × n) matrix of coefficients of the exogenous variables It is assumed that ζ is uncorrelated with the exogenous variables, and B is supposed to have zeros in its diagonal (i.e., an endogenous variable does not influence itself) and to satisfy the assumption that (I − B) is nonsingular, where I is the identity matrix. The covariance matrices of this model are the following: Φ = Exx T is the (n × n) covariance matrix of the exogenous variables Ψ = Eζζ T is the (m × m) covariance matrix of the errors If z is a vector containing all the p = m + n variables, exogenous and endogenous, in the following order: z T = x1 … xn , y1 … ym (11.2) then the observed covariances can be expressed as Σobs = (1(N − 1))⋅Z⋅ZT (11.3) where Z is the p × N matrix of the p observed variables for N observations. The covariance matrix implied by the model can be obtained as follows: (11.4) Σmod ==      E EE EE T TT TT zz xx xy yx yy Copyright 2005 by Taylor Francis Group, LLC 402 Medical Image Analysis where Eyy T = E(I − B) −1 (Γx + ζ)(Γx + ζ) T ((I −B) −1 ) T = (I −B) −1 (ΓΦΓ + Ψ) ((I − B) −1 ) T (11.5) because the errors ζare not correlated with the x, and where Exx T = Φ (11.6) Exy T = (I − B) −1 Φ (11.7) Eyx T = ((I − B) −1 Φ) T (11.8) because Σmod is symmetric. The resulting covariance matrix, in terms of the model parameters, is the following: (11.9) Without other constraints, the problem of the minimizing the differences between the observed covariances and those implied by the model is undetermined, because the number of variables (elements of matrices B, Γ, Ψ, and Φ) is greater than the number of equations (m + n)(m + n + 1)2. For this reason, the SEM technique is based on the a priori formulation of a model on the basis of anatomical and physiological constraints. This model implies the existence of just some causal relationships among variables, represented by arcs in a “path” diagram; all the parameters related to arcs not present in the hypothesized model are forced to zero. For this reason, all the parameters to be estimated are called free parameters. If t is the number of free parameters, it must be that t ≤(m + n)(m + n + 1)2. These parameters are estimated by minimizing a function of the observed and implied covariance matrices. The most widely used objective function for SEM is the maximum likelihood (ML) function: FML = log|Σmod| + tr(Σobs ⋅Σmod −1 ) − log|Σobs | − p (11.10) where tr(·) is the trace of matrix. In the context of multivariate, normally distributed variables, the minimum of the ML function multiplied by (N − 1) follows a χ 2 distribution with p(p + 1)2 – t degrees of freedom, where t is the number of parameters to be estimated, and p is the total number of observed variables (endogenous + exogenous). The χ 2 statistic test can then be used to infer statistical significance of the structural equation model obtained. In the present study, the software package LISREL 46 was used to implement the SEM technique. Σ ΦΦΦΦ ΦΦΓΓΦ ΦΓΓΨΨ mod= − () − () ()− () + ()− ( − −− IB IB IB IB 1 11T )) ()         −1 T Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 403 11.2.3 DIRECTEDTRANSFERFUNCTION In this study, the DTF technique was applied to the set of cortical estimated waveforms S z(t)= z 1 (t), z 2 (t), …, z N (t) T (11.11) obtained for the N ROIs considered, as will be described in detail in the following sections. The following MVAR process is an adequate description of the data set Z. , with (0) = I (11.12) where e(t) is a vector of a multivariate zeromean uncorrelated white noise process; (1), (2), …, (q) are the N × N matrices of model coefficients, and q is the model order chosen, in our case, with the Akaike information criterion for MVAR processes 37. To investigate the spectral properties of the examined process, Equation 11.12 is transformed to the frequency domain (f) Z(f) = E(f) (11.13) where (11.14) and t is the temporal interval between two samples. Equation 11.13 can then be rewritten as Z(f) = Λ−1 (f) E(f) = H(f) E(f) (11.15) Here, H(f) is the transfer matrix of the system whose element Hij represents the connection between the jth input and the ith output of the system. With these definitions, the causal influence of the cortical waveform estimated in the jth ROI on that estimated in the ith ROI (the directed transfer function θ 2 ij (f)) is defined as (11.16) To enable comparison of the results obtained for cortical waveforms with different power spectra, a normalization was performed by dividing each estimated DTF by the squared sums of all elements of the relevant row, thus obtaining the socalled normalized DTF 36 Λktk t k q () − ()= () = ∑ ze 0 ΛΛΛΛ fkejftk k q ()= ()− = ∑ 2 0 π∆ θij ij fHf 2 2 ()= () Copyright 2005 by Taylor Francis Group, LLC 404 Medical Image Analysis (11.17) where γ ij (f) expresses the ratio of influence of the cortical waveform estimated in the jth ROI on the cortical waveform estimated on the ith ROI, with respect to the influence of all the estimated cortical waveforms. Normalized DTF values are in the interval 47, and the normalization condition (11.18) is applied. 11.2.4 COMPUTERSIMULATION 11.2.4.1 The Simulation Study The experimental design we adopted was meant to analyze the recovery of the connectivity patterns obtained under the different levels of SNR and signal temporal length that were imposed during the generation of sets of test signals simulating cortical average activations. As described in the following subsections, the simulated signals were obtained from actual cortical data estimated with the highresolution EEG procedures available at the highresolution EEG Laboratory of the University of Rome. 11.2.4.2 Signal Generation for the SEM Methodology Different sets of test signals were generated to fit an imposed connectivity pattern (shown in Figure 11.2)and to respect imposed levels of temporal duration (LENGTH) and signaltonoise ratio (SNR). In the following discussion, using a more compact notation, signals have been represented with the z vector defined in Equation 11.2, containing both the endogenous and the exogenous variables. Channel z 1 is a referencesource waveform, estimated from a highresolution EEG (128 electrodes) recording in a healthy subject during the execution of unaimed selfpaced movements of the right finger. Signals z 2 , z 3 , and z 4were obtained by the contribution of signals from all other channels, with an amplitude variation plus zeromean uncorrelated white noise processes with appropriate variances, as shown in Equation 11.19 zk = Azk + Wk (11.19) where zk is the 4×1 vector of signals, Wk is the 4×1 noise vector, and A is the 4×4 parameters matrix obtained from the Γand Bmatrices in the following way: γ ij ij im m N f Hf Hf 2 2 2 1 ()= () () = ∑ γ in n N f 2 1 1 ()= = ∑ Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 405 (11.20) where βij stands for the generic (i,j) element of the B matrix, and γ i is the ith element of the vector Γ. All procedures of signal generation were repeated under the following conditions: SNR factor levels = (1, 3, 5, 10, 100) LENGTH factor levels = (60, 190, 310, 610) sec. This corresponds, for instance, to (120, 380, 620, 1220) EEG epochs, each of which is 500 msec long. It is worth noting that the levels chosen for both SNR and LENGTH factors cover the typical range for the cortical activity estimated with highresolution EEG techniques. FIGURE 11.2 Connectivity pattern imposed in the generation of simulated signals. z 1 , …, z 4 represent the average activities in four cortical areas. Values on the arcs represent the connection’s strength (a21 = 1.4, a31 = 1.1, a32 = 0.5, a42 = 0.7, a43 = 1.2). a42 Z2 Z4 Z3 Z1 a32 a31 a21 a43 A=    00 0 0 1111213 2212223 3313233 γβ β β γβ β β γβ β β        =          aa aa 11 14 41 44       Copyright 2005 by Taylor Francis Group, LLC 406 Medical Image Analysis 11.2.4.3 Signal Generation for the DTF Methodology Different sets of test signals were generated to fit an imposed coupling scheme involving four different cortical areas (shown in Figure 11.2)while also respecting imposed levels of signaltonoise ratio (factor SNR) and duration (factor LENGTH). Signal z 1 (t) was a reference cortical waveform estimated from a highresolution EEG (96 electrodes) recording in a healthy subject during the execution of selfpaced movements of the left finger. Subsequent signals z 2 (t) to z 4 (t) were iteratively obtained according to the imposed scheme (Figure 11.2)by adding to signal z j contributions from the other signals, delayed by intervals τ ij and amplified by factors aij plus an uncorrelated Gaussian white noise. Coefficients of the connection strengths were chosen in a range of realistic values as met in previous studies during the application of other connectivityestimation techniques, such as structural equation modeling, in several memory, motor, and sensory tasks 7. Here, the values used for the connection strength were a21 = 1.4, a31 = 1.1, a32 = 0.5, a42 = 0.7, and a43 = 1.2. The values used for the delay from the ith ROI to the jth one (τ ij) ranged from one sample up to the q − 2, where q was the order of the MVAR model used. Because the statistical analysis performed with different values of such delay samples returned the same information with respect to the variation of this parameter, in the following we particularized the results to the case τ 21 = τ 31 = τ 32 = τ 42 = τ 43 = 1 sample, which for a sampling rate of 64 Hz became a delay of 15 msec. All procedures of signal generation were repeated under the following conditions: SNR factor levels = (0.1, 1, 3, 5, 10) LENGTH factor levels = (960, 2,880, 4,800, 9,600, 19,200, 38,400) data samples, corresponding to signals length of (15, 45, 75, 150, 300, 600) sec at a sampling rate of 64 Hz, or to (7, 22, 37, 75, 150, 300) EEG trials of 2 sec each The levels chosen for both SNR and LENGTH factors cover the typical range for the cortical activity estimated with highresolution EEG techniques. The MVAR model was estimated by means of the NuttallStrand method or the multivariate Burg algorithm, which is one of the most common estimators for MVAR models and has been demonstrated to provide the most accurate results 48–50. 11.2.4.4 Performance Evaluation The quality of the performed estimation was evaluated using the Frobenius norm of the matrix, which reports the differences between the values of the estimated (via SEM) and the imposed connections (relative error). The norm was computed for the connectivity patterns obtained with the SEM methodology (11.21) E aa a ij j m ij i m ij j m i relative = − = = = ∑ ∑ ∑ ( ˆ ) () 1 2 1 1 2 == ∑ 1 m Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 407 In the case in which the DTF method was used, the statistical evaluation of DTF performances required a precise definition of an error function describing the goodness of the pattern recognition performed. This was achieved by focusing on the MVAR model structure described in Equation 11.12 and comparing it with the signalsgeneration scheme. The elements of matrices (k) of MVAR model coefficients can be put in relation with the coefficients used in the signal generation, and they are different from zero only for k = τ ij , where τ ij is the delay chosen for each pair ijof ROIs and for each direction among them. In particular, for the independent reference source waveform z 1 (t), an autoregressive model of the same order of the MVAR has been estimated, whose coefficients a11 (1), …, a11 (q) correspond to the elements Λ11 (1), …, Λ11 (q) of the MVAR coefficients matrix. Thus, with the estimation of the MVAR model parameters, we aim to recover the original coefficients aij (k) used in signal generation. In this way, reference DTF functions have been computed on the basis of the signalgeneration parameters. The error function was then computed as the difference between these reference functions and the estimated ones (both averaged in the frequency band of interest). To evaluate the performances in retrieving the connections between areas, the same index used in the case of the SEM was adopted, but with light differences of notation, i.e., the Frobenius norm of the matrix reporting the differences between the values of the estimated and the imposed connections (total relative error) (11.22) In Equation 11.22, represents the average value of the DTF function from j to i within the frequency band of interest. For both SEM and DTF, the simulations were performed by repeating each generationestimation procedure 50 times to increase the robustness of the successive statistical analysis. 11.2.4.5 Statistical Analysis The results obtained were subjected to separate ANOVA. The main factors of the ANOVAs for the DTF method were the SNR (with five levels: 0.1, 1, 3, 5, 10) and the signal LENGTH (with six levels: 960, 2,880, 4,800, 9,600, 19,200, 38,400 data samples, equivalent to 15, 45, 75, 150, 300, 600 sec at 64 Hz of sampling rate). In the case of the SEM method, the main factors were identical, but the LENGTH has only four levels (equal to 60, 190, 310, and 610 sec at 64 Hz). For all of the methodologies used, ANOVA was performed on the error index that was adopted (relative error). The correction of GreenhouseGasser for the violation of the spherical hypothesis was used. The post hoc analysis with the Duncan test at the p = 0.05 statistical significance level was then performed. E ff ij j m ij i relative band band = − = = ∑(() ˆ () ) γγ 1 2 1 mm ij j m i m f ∑ ∑ ∑ = = (() ) γ band 1 2 1 γ ij f () band Copyright 2005 by Taylor Francis Group, LLC 408 Medical Image Analysis 11.2.5 APPLICATION TOMOVEMENTRELATEDPOTENTIALS The estimation of connectivity patterns by using the DTF and SEM on highresolution EEG recordings was applied to the analysis of a simple movement task. In particular, we considered a righthand fingertapping movement that was externally paced by a visual stimulus. This task was chosen because it has been very widely studied in literature with various brainimaging techniques such as EEG or fMRI 51–53. 11.2.5.1 Subject and Experimental Design Three righthanded healthy subjects (age 23.3 ± 0.58, one male and two females) participated in the study after providing informed consent. Subjects were seated comfortably in an armchair with both arms relaxed and resting on pillows, and they were asked to perform fast, repetitive rightfinger movements. During this motor task, the subjects were instructed to avoid eye blinks, swallowing, or any movement other than the required finger movements. 11.2.5.2 Head and Cortical Models A realistic head model of the subjects, reconstructed from T1weighted MRIs, was employed in this study. Scalp, skull, and dura mater compartments were segmented from MRIs with software originally developed at the Department of Human Physiology of Rome, and such structures were triangulated with about 1,000 triangles for each surface. The source model was built with the following procedure: 1. The cortex compartment was segmented from MRIs and triangulated to obtain a fine mesh with about 100,000 triangles. 2. A coarser mesh was obtained by resampling the fine mesh to about 5,000 triangles. The downsampling was performed with an adaptive algorithm designed to represent with a sufficient number of triangles the parts of the cortex where the radius of curvature was high (for instance, during the bending of a sulcus) while attempting to represent with few triangles the flatter parts of the cortical surface (for instance, on the upper part of the gyri). 3. An orthogonal unitary equivalentcurrent dipole was placed in each node of the triangulated surface, with its direction parallel to the vector sum of the normals to the surrounding triangles. 11.2.5.3 EEG Recordings Eventrelated potential (ERP) data were recorded with 96 electrodes; data were recorded with a leftear reference and submitted to an artifactremoval process. Six hundred ERP trials of 600 msec of duration were acquired. The analog–digital sampling rate was 250 Hz. The surface electromyographic (EMG) activity of the muscle was also collected. The onset of the EMG response served as zero time. All data were visually inspected, and trials containing artifacts were rejected. We used Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 409 semiautomatic supervised threshold criteria for the rejection of trials contaminated by ocular and EMG artifacts, as described in detail elsewhere 54. After the EEG recording, the electrode positions were digitized using a threedimensional localization device with respect to the anatomic landmarks of the head (nasion and two preauricular points). The analysis period for the potentials timelocked to the movement execution was set from 300 msec before to 300 msec after the EMG trigger (zero time). The ERP time course was divided into two phases relative to the EMG onset: the first, labeled as “PRE” period, marked the 300 msec before the EMG onset and was intended as a generic preparation period; the second, labeled as “POST,” lasted up to 300 msec after the EMG onset and was intended to signal the arrival of the movement somatosensory feedback. We kept the same PRE and POST nomenclature for the signals estimated at the cortical level. 11.2.5.4 Statistical Evaluation of Connectivity Measurements by SEM and DTF As described previously, the statistical significance of the connectivity pattern estimated with the SEM technique was ensured by the fact that — in the context of the multivariate, normally distributed variables — the minimum of the maximum likelihood function FML, multiplied by (N − 1), follows a χ 2 distribution with p(p+ 1)2 − t degrees of freedom, where t is the number of parameters to be estimated, and p is the total number of observed variables (endogenous + exogenous). Then, the χ 2 statistic test can be used to infer the statistical significance of the structural equation model obtained. The situation for the statistical significance of the DTF measurements is different because the DTF functions have a highly nonlinear relation to the timeseries data from which they are derived, and the distribution of their estimators is not well established. This makes tests of significance difficult to perform. A possible solution to this problem was proposed by Kaminski et al. 37. Their solution involves the use of a surrogate data technique 55 in which an empirical distribution for random fluctuations of a given estimated quantity is generated by estimating the same quantity from several realizations of surrogate data sets where the deterministic interdependency between variables has been removed. To ensure that all features of each data set are as similar as possible to the original data set, with the exception of channel coupling, the very same data are used, and any timelocked coupling between channels is disrupted by shuffling phases of the original multivariate signal. Because the EEG signal had been divided into single trials, each surrogate data set was built up by scrambling the order of epochs, using different sequences for each channel. In this procedure, every singlechannel EEG epoch was used once and only once, and only occasionally (and with a very low probability), two channels in the same surrogate trial came from the same actual trial. The set properties of univariate surrogate signals are not influenced by this shuffling procedure, because only the epoch order is varied. Moreover, because no shuffling was performed between single samples, the temporal correlation, and thus the spectral features, of univariate signals is the same for the original and surrogate data sets, thus making it possible to estimate different distributions of DTF fluctuations for each frequency band. A total of 1000 Copyright 2005 by Taylor Francis Group, LLC 410 Medical Image Analysis surrogate data sets was generated, as described previously, and DTF spectra were estimated from each data set. For each channel pair and for each frequency bin, the 99th percentile was computed and subsequently considered as a significance threshold. 11.2.5.5 Estimation of Cortical Source Current Density The solution of the following linear system Lz = d + e (11.23) provides an estimate of the dipole source configuration z that generates the measured EEG potential distribution d. The system also includes the measurement noise n, assumed to be normally distributed 39. In Equation 11.23, L is the lead field, or the forward transmission matrix, in which each jth column describes the potential distribution generated on the scalp electrodes by thejth unitary dipole. The currentdensity solution vector ξ was obtained as follows 39: (11.24) where M, N are the matrices associated with the metrics of the data and of the source space, respectively, λ is the regularization parameter, and ||z||M represents the Mnorm of the vector z. The solution of Equation 11.24 is given by the inverse operator G as follows: , (11.25) An optimal regularization of this linear system was obtained by the Lcurve approach 56, 57. As a metric in the data space, we used the identity matrix, but in the source space, we use the following metric as a norm (11.26) where (N−1 ) ii is the ith element of the inverse of the diagonal matrix N, and all the other matrix elements Nij , for each i j, are set to 0. The L2 norm of the ith column of the lead field matrix L is denoted by ||L.i ||. Here, we present two characterizations of the source metric N that can provide the basis for the inclusion of the information about the statistical hemodynamic activation of ith cortical voxel into the linearinverse estimation of the cortical source activity. In the fMRI analysis, several methods have been developed to quantify the brain hemodynamic response to a particular task. However, in the following, we ξ= − + () arg min z Lz d z MN 2 2 2 λ ξ=Gb GNLLNL M = ′′+ () −− −− 11 11 λ N − ⋅ − ()= 1 2 ii i L Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 411 analyze the case in which a particular fMRI quantification technique — the percent change (PC) technique — has been used. This measure quantifies the percent increase of the fMRI signal during the task performance with respect to the rest state 58. The visualization of the voxels’ distribution in the brain space that is statistically increased during the task condition with respect to the rest is called the PC map. The difference between the mean rest and movementrelated signal intensity is generally calculated voxel by voxel. The restrelated fMRI signal intensity is obtained by averaging the premovement and recovery fMRI. A Bonferronicorrected student’s ttest is also used to minimize alphainflation effects due to multiple statistical voxelbyvoxel comparisons (Type I error; p < 0.05). The introduction of fMRI priors into the linearinverse estimation produces a bias in the estimation of the currentdensity strength of the modeled cortical dipoles. Statistically significantly activated fMRI voxels, which are returned by the percentage change approach 58, are weighted to account for the EEGmeasured potentials. In fact, a reasonable hypothesis is that there is a positive correlation between local electric or magnetic activity and local hemodynamic response over time. This correlation can be expressed as a decrease of the cost in the functional PHI of Equation 11.24 for the sources zj in which fMRI activation can be observed. This increases the probability for those particular sources z j to be present in the solution of the electromagnetic problem. Such thoughts can be formalized by particularizing the source metric N to take into account the information coming from the fMRI. The inverse of the resulting metric is then proposed as follows 59: (11.27) in which (N−1 ) ii and ||A⋅i|| have the same meaning as described previously. The term g(αi ) is a function of the statistically significant percentage increase of the fMRI signal assigned to the ith dipole of the modeled source space. This function is expressed as (11.28) where αi is the percentage increase of the fMRI signal during the task state for the ith voxel, and the factor K tunes fMRI constraints in the source space. Fixing K= 1 lets us disregard fMRI priors, thus returning to a purely electrical solution; a value for K» 1 allows only the sources associated with fMRI active voxels to participate in the solution. It was shown that a value for K on the order of 10 (90% of constraints for the fMRI information) is useful to avoid mislocalization due to overconstrained solutions 60–62. In the discussion that follows, the estimation of the cortical activity obtained with this metric will be denoted as diagfMRI, because the previous definition of the source metric N results in a matrix in which the offdiagonal elements are zero. NA− ⋅ − ()= 122 ii ii g() α gK K i i i i () max( ) ,, α α α α 2 11 1 0 =+ − () ≥≥ Copyright 2005 by Taylor Francis Group, LLC 412 Medical Image Analysis 11.2.5.6 Regions of Interest (ROIs) Several cortical regions of interest (ROIs) were drawn by two independent and expert neuroradiologists on the computerbased cortical reconstruction of the individual head models. In cases where the SEM methodology was adopted, we selected ROIs based on previously available knowledge about the flow of connections between different cortical macroareas, as derived from neuroanatomy and fMRI studies. In particular, information flows were hypothesized to exist from the parietal (P) areas toward the sensorimotor (SM), the premotor (PM), and the prefrontal (PF) areas 63–65. The prefrontal areas (PF) were defined by including the Brodmann areas 8, 9, and 46; the premotor areas (PM) by including the Brodmann area 6; the sensorimotor areas (SM) by including the Brodmann areas 4, 3, 2, and 1; and the parietal areas (P), generated by the union of the Brodmann areas 5 and 7 (see colored areas in Figure 11.3). In cases where the DTF method was used, we selected the ROIs representing the left and right primary somatosensory (S1) areas, which included the Brodmann areas (BA) 3, 2, 1, while the ROIs representing the left and right primary motor (MI) included the BA 4. The ROIs representing the supplementary motor area (SMA) were obtained from the cortical voxels belonging to the BA 6. We further separated the proper and anterior SMA indicated into regions labeled BA 6P and 6A, respectively. Furthermore, ROIs from the right and the left parietal areas (BA 5, 7) and the occipital areas (BA 19) were also considered. In the frontal regions, the BA 46, 8, 9 were also selected (see Color Figure 11.4following page 274.). 11.2.5.7 Cortical Current Waveforms By using the relations described above, at each time point of the gathered ERP data, an estimate of the signed magnitude of the dipolar moment for each of the 5000 cortical dipoles was obtained. In fact, since the orientation of the dipole was already defined to be perpendicular to the local cortical surface of the model, the estimation process returned a scalar rather than a vector field. To obtain the cortical current waveforms for all the time points of the recorded EEG time series, we used a unique quasioptimal regularization λ value for all the analyzed EEG potential distributions. This quasioptimal regularization value was computed as an average of the several λ values obtained by solving the linearinverse problem for a series of EEG potential distributions. These distributions are characterized by an average global field power (GFP) with respect to the higher and lower GFP values obtained during all the recorded waveforms. The instantaneous average of the dipole’s signed magnitude belonging to a particular ROI generates the representative time value of the cortical activity in that given ROI. By iterating this procedure on all the time instants of the gathered ERP, the cortical ROI currentdensity waveforms were obtained, and they could be taken as representative of the average activity of the ROI during the task performed by the experimental subjects. These waveforms could then be subjected to the SEM and DTF processing to estimate the connectivity pattern between ROIs, by taking into account the timevarying increase or decrease of the power spectra in the Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 413 FIGURE 11.3 Cortical connectivity patterns obtained with the SEM method for the period preceding and following the movement onset in the alpha (8 to 12 Hz) frequency band. The patterns are shown on the realistic head model and cortical envelope (obtained from sequential MRIs) of the subject analyzed. Functional connections are represented with arrows moving from one cortical area to another. The colors and sizes of the arrows code the strengths of the functional connectivity observed between ROIs. The labels are relative to the name of the ROIs employed. (a) Connectivity pattern obtained from ERP data before the onset of the rightfinger movement (electromyographic onset, EMG). (b) Connectivity patterns obtained after the EMG onset. 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 (a) (b) SMr SMr PMr PMr PFr PFr Pr PI PFI PFI PMI PMI SMI SMI PI Copyright 2005 by Taylor Francis Group, LLC 414 Medical Image Analysis FIGURE 11.4 Cortical connectivity patterns obtained with the DTF method for the period preceding and following the movement onset in the alpha (8 to 12 Hz) frequency band. The patterns are shown on the realistic head model and cortical envelope (obtained from sequential MRIs) of the subject analyzed. Functional connections are represented with arrows moving from one cortical area to another. The colors and sizes of the arrows code the strengths of the connections. (a) Connectivity pattern obtained from ERP data before the onset of the rightfinger movement (electromyographic onset, EMG). (b) Connectivity patterns obtained after the EMG onset. (a) (b) 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 415 frequency bands of interest. Here, we present the results obtained for the connectivity pattern in the alpha band (8 to 12 Hz), because the ERP data related to the movement preparation and execution are particularly responsive within this frequency interval (for a review, see Pfurtscheller and Lopes da Silva 32). 11.3 RESULTS 11.3.1 COMPUTERSIMULATIONS FOR SEM Each set of signals was generated as described in the Methods section (Section 11.2) to fit a predefined connection model as well as to respect different levels of the two factors SNR and LENGTH of the recordings. The resulting signals were analyzed by means of the freeware software LISREL, which gave as a result an estimation of the connection strengths. Figure 11.2shows the connection model used in the signal generation and in the parameter estimation. The arrows represent the existence of a connection directed from the signal z i toward the signal z j, and the values on the arcs aij represent the connection parameters described in Equation 11.20. The results obtained for the statistical analysis performed on the 50 repetitions of the procedure are reported in Figure 11.5,representing the plot of means of the relative error with respect to signal LENGTH and SNR. ANOVA has identified a strong statistical significance of both factors considered. The factors SNR and LENGTH were both highly significant (factor LENGTH F = 288.60, p < 0.0001; factor SNR F = 22.70, p < 0.0001). Figure 11.5(a) shows the plot of means of the relative error with respect to the signal length levels, which reveals a decrease of the connectivity estimation error with an increase in the length of the available data. Figure 11.5(b) shows the plot of means with respect to the different SNR levels employed in the simulation. Because the main factors were found highly statistically significant, post hoc tests (Duncan at 5%) were then applied. Such tests showed statistically significant differences between all levels of the factor LENGTH, although there is no statistically significant difference between levels 3, 5, and 10 of the factor SNR. 11.3.2 COMPUTERSIMULATIONS FOR DTF The connectivity model used in the signal generation was the same as was used for the SEM simulation, which is shown in Figure 11.2.A multivariate autoregressive model of order 8 was fitted to each set of simulated data. Then, the normalized DTF functions were computed from each autoregressive model. The procedure of signal generation and DTF estimation was carried out 50 times for each level of factors SNR and LENGTH. The index of performances used, i.e., the relative error, was computed for each generationestimation procedure performed and then subjected to ANOVA. In this statistical analysis, relative error was the dependent variable, and the different SNR and LENGTH imposed in the signal generation were the main factors. ANOVA revealed a strong statistical influence of all the main factors (SNR and LENGTH; for relative error we obtained: SNR: F = 3295.5, p < 0.0001; LENGTH: F = 1012.4, p < 0.0001). Copyright 2005 by Taylor Francis Group, LLC 416 Medical Image Analysis FIGURE 11.5 (Color figure follows p. 274.)Results of ANOVA performed on the relative error resulting from SEM simulations. (a) Plot of means with respect to signal LENGTH as a function of time (seconds). ANOVA shows a high statistical significance for factor LENGTH (F = 288.60, p < 0.0001). Duncan post hoctest (performed at 5% level of significance) shows statistically significant differences between all levels. (b) Plot of means with respect to signaltonoise ratio. Here, too, a high statistical influence of factor SNR on the error in the estimation is shown (F = 22.70, p < 0.0001). Duncan post hoc test (performed at 5% level of significance) shows that there is no statistically significant difference between levels 3, 5, and 10 of factor SNR. Relative Error 0.050 0.045 0.040 0.035 0.030 0.025 0.020 0.015 0.010 60 190 Length (sec) (a) 310 610 Relative Error 0.036 0.034 0.032 0.030 0.028 0.026 0.024 0.022 0.020 13SNR (b) 510100 Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 417 Figure 11.6shows the influence of factors SNR and LENGTH on relative error. In detail, Figure 11.6(a) shows the plot of means of the relative error with respect to the signal LENGTH levels, which reveals a decrease of the connectivity estimation error with an increase in the length of the available data; Figure 11.6(b) shows the plot of means with respect to different SNR levels employed in the simulation. In particular, for a SNR between 3 and 10, the expected error in the estimation of the connectivity pattern was generally under 7%, and the same values were obtained for ERP recording longer than 150 sec. Because the main factors were found to be statistically significant, post hoc tests (Duncan test at 5%) were then applied. The results showed statistically significant differences between the levels 15 and 45 sec (960 and 2880 samples, respectively) of the factor LENGTH and the other levels, but there is no statistically significant difference between levels 3, 5, and 10 of the factor SNR. 11.3.3 APPLICATION TOHIGHRESOLUTIONEVENTRELATED POTENTIALRECORDINGS The results of the application of the SEM method for estimating the connectivity on the eventrelated potential recordings is depicted in Figure 11.3,which shows the statistically significant cortical connectivity patterns obtained for the period preceding the movement onset in subject no. 1, in the alpha frequency band. Each pattern is represented with arrows that connect one cortical area (the source) to another one (the target). The colors and sizes of arrows code the level of strength of the functional connectivity observed between ROIs. The labels indicate the names of the ROIs employed. Note that the connectivity pattern during the period preceding the movement in the alpha band involves mainly the parietal left ROI (Pl) coincident with Brodmann areas 5 and 7 functionally connected to the left and right premotor cortical ROIs (PMl and PMr), the left sensorimotor area (SMl), and both the prefrontal ROIs (PFl and PFr). The stronger functional connections are relative to the link between the left parietal and the premotor areas of both cerebral hemispheres. After the preparation and the beginning of the finger movement in the POST period, changes in the connectivity pattern can be noted. In particular, the origin of the functional connectivity links is positioned in the sensorimotor left cortical areas (SMl). From there, functional links are established with prefrontal left (PFl) and both the premotor areas (PMl and PMr). A functional link emerged in this condition connecting the right parietal area (Pr) with the right sensorimotor area (SMr). The left parietal area (Pl) that was so active in the previous condition was instead linked with the left sensorimotor (SMl) and right premotor (PMr) cortical areas. Connectivity estimations performed by DTF on the movementrelated potentials were first analyzed from a statistical point of view via the previously described shuffling procedure. The order of the MVAR model used for each DTF estimation had to be determined for each subject and in each temporal interval of the cortical waveform segmentations (PRE and POST interval). The Akaike information criterion (AIC) procedure was used and returned an optimal order between 6 and 7 for all the subjects in both PRE and POST intervals. On such cortical waveforms, the DTF computational procedure described in the Methods section (Section 11.1) was Copyright 2005 by Taylor Francis Group, LLC 418 Medical Image Analysis FIGURE 11.6(Color figure follows p. 274.)Results of ANOVA performed on the relative error resulting from DTF simulations. (a) Plot of means with respect to signal LENGTH as a function of time (seconds). ANOVA shows a high statistical significance for factor LENGTH (F = 1012.36, p < 0.0001). Duncan post hoc test (performed at 5% level of significance) shows statistically significant differences between levels 15 and 45 sec at 64Hz sampling rate (equivalent of 960 and 2880 samples, respectively) of the factor LENGTH and all the other levels. (b) Plot of means with respect to signaltonoise ratio. Here, too, a high statistical influence of factor SNR on the error in the estimation is shown (F = 3295.45, p < 0.0001). Duncan post hoc test (performed at 5% level of significance) shows that there is no statistically significant difference between levels 3, 5, and 10 of factor SNR. 0.14 0.13 0.12 0.11 0.10 0.09 0.08 0.07 0.06 0.05 15 45 75 150 300 600 Relative Error Length (sec) (a) 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.1 1 3 5 10 Relative Error SNR (b) Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 419 applied. Figure 11.4shows the cortical connectivity patterns obtained for the period preceding and following the movement onset in subject no. 1. Here, we present the results obtained for the connectivity pattern in the alpha band (8 to 12 Hz), as the ERP data related to the movement preparation and execution are particularly responsive within this frequency interval (for a review, see Pfurtscheller and Lopes da Silva 32). The taskrelated pattern of cortical connectivity was obtained by calculating the DTF between the cortical currentdensity waveforms estimated in each ROI depicted on the realistic cortex model. The connectivity patterns between the ROIs are represented by arrows pointing from one cortical area to another. The arrows’ color and size code the strength of the functional connectivity estimated between the source and the target ROI. Labels indicate the ROIs involved in the estimated connectivity pattern. Only the cortical connections statistically significant at p < 0.01 are represented, according to the thresholds obtained by the shuffling procedure. It can be noted that the connectivity patterns during the period preceding and following the movement in the alpha band involve bilaterally the parietal and sensorimotor ROIs, which are also functionally connected with the premotor cortical ROIs. A minor involvement of the prefrontal ROIs is also observed. The stronger functional connections are relative to the link between the premotor and prefrontal areas of both cerebral hemispheres. After the preparation and the beginning of the finger movement in the POST period, slight changes in the connectivity patterns can be noted. 11.3.4 APPLICATION OF THEMULTIMODAL EEGFMRI INTEGRATIONTECHNIQUES TO THEESTIMATION OFSOURCES OFSELFPACEDMOVEMENTS In this section, we provide a practical example of the application of the multimodal integration techniques of EEG and fMRI (as theoretically described in the previous sections) to the problem of detection of neural sources subserving unilateral selfpaced movements in humans. The highresolution EEG recordings (128 scalp electrodes) were performed on normal healthy subjects by using the facilities available at the laboratory of the Department of Human Physiology, University of Rome. Realistic head models were used, each one provided with a cortical surface reconstruction tessellated with 3000 current dipoles. Separate block design and eventrelated fMRI recordings of the same subjects were performed by using the facilities of the Instituto Tecnologie Avanzate Biomediche (ITAB) of Chiety, Italy. Distributed linearinverse solutions by using hemodynamic constraints were obtained according to the previously described methodology. Figure 11.7presents the typical situation that occurred when different imaging methods were used to characterize the brain activity generated during a specific task. In particular, the task performed by the subject was the selfpaced movement of the middle finger of the right hand. This task was performed three times under three different scanners, namely the fMRI, the HREEG, and the MEG. On the left of Figure 11.7,there is a view of some cerebral areas active during the movement, as reported by fMRI. The maximum values of the fMRI responses are located in the Copyright 2005 by Taylor Francis Group, LLC 420 Medical Image Analysis voxels roughly corresponding to the primary somatosensory and motor areas (hand representation) contralateral to the movement. In fact, during the selfpaced unilateral finger extension, somatosensory reafference inputs from finger joints as well as cutaneous nerves are directed to the primary somatosensory area, while centrifugal commands from the primary motor area are directed toward the spinal cord via the pyramidal system. At the center of the figure is represented the dura mater potential distribution estimated with the use of the SL operator over a cortical surface reconstruction. The deblurred distribution is obtained at 100 msec after the EMG onset of the right middle finger. Note the characteristic reverse negative and positive SL fields on the left hemisphere. It is easy to appreciate the different time resolutions of the different techniques, with the fMRI data being relative to the whole time course of the experiment, and the highresolution EEG data being relative to a particular span of milliseconds of the cortical electromagnetic field evolution related to the same experiment. Simulations performed to test the efficacy of the multimodal integration of HREEG and fMRI return the information that the inclusion of fMRI priors improves the reconstruction of cortical activity 22, 60. Figure 11.8(a) presents three cortical currentdensity distributions. The left one shows the cortical regions roughly corresponding to the supplementary motor area and the left motor cortex, with the imposed activations represented in black. The imposed activations generated a potential distribution over the scalp electrodes (not shown in the figure). From this potential distribution, different inverse operators with and without the use of fMRI priors (located in the supplementary and left motor areas) attempted to estimate the currentdensity distribution. The currentdensity reconstruction at the center of Figure 11.8(a) shows the results of the estimation of sources presented on the left map (obtained using the minimumnorm estimate procedure) without the use of fMRI FIGURE 11.7 (Color figure follows p. 274.) (Left) A view of some cerebral areas active during the selfpaced movement of the right finger, as reported by fMRI. (Right) Dura mater potential distribution estimated with the use of the SL operator over a cortical surface reconstruction. The deblurred distribution is obtained at 100 msec after the EMG onset of the right middle finger. Copyright 2005 by Taylor Francis Group, LLC Estimation of Human Cortical Connectivity 421 priors. The currentdensity reconstruction on the right of the figure presents the cortical activations recovered by the use of fMRI priors in agreement with the Equation 11.27. Figure 11.8(b) illustrates the cortical distributions of the current density (estimated with the linearinverse approaches from the potential distribution relative to the movement preparation) about 200 msec before the extension of a right middle finger. Such an approach used no fMRI constraint as well the fMRI constraints based FIGURE 11.8 (Color figure follows p. 274.) (a) Three cortical currentdensity distributions. The left one shows the simulated cortical regions roughly corresponding to the supplementary motor area and the left motor cortex, with the imposed activations represented in black. The currentdensity reconstruction at the center of the figure presents the results of the estimation of sources (obtained using the minimumnorm estimate procedure) presented on the left map without the use of fMRI priors. The currentdensity reconstruction on the right of the figure presents the cortical activations recovered by the use of fMRI priors in agreement with Equation 11.27. (b) Distributions of the current density estimated with the linearinverse approaches from the potential distribution relative to the movement preparation, about 200 msec before a right middle finger extension. The distributions are represented on the realistic subject’s head volume conductor model. (Left) Scalp potential distribution recorded 200 msec before movement execution. (Center) Cortical estimate obtained without the use of fMRI constraints, based on the minimumnorm solutions. (Right) Cortical estimate obtained with the use of fMRI constraints based on Equation 11.27. Original Minimum Norm fMRI–constrained Scalp potential Minimum Norm fMRI–constrained (a) (b) 1 0.8 0.6 0.4 0.2 −0.2 −0.4 −0.6 −0.8 −1 0 1 0.8 0.6 0.4 0.2 −0.2 −0.4 −0.6 −0.8 −1 0 0.4 0.3 0.2 0.1 −0.1 −0.2 −0.3 −0.4 0 Copyright 2005 by Taylor Francis Group, LLC 422 Medical Image Analysis on Equations 11.27 and 11.28. The left of Figure 11.8(b) shows the topographic map of readiness potential distribution recorded at the
Xem thêm

38 Đọc thêm

Đề thi thử môn anh đáp án chi tiet nam 2016 đề 1

ĐỀ THI THỬ MÔN ANH ĐÁP ÁN CHI TIET NAM 2016 ĐỀ 1

Họ và tên thí sinh:…………………………………………. Số báo danh:……………………………………………….. Mã đề số 423 A. PHẦN TRẮC NGHIỆM (64 Question; 8 điểm) I. Mark the letter A, B, C, D on your answer sheet to indicate the word whose underlined part differs from the other three in pronunciation in each of the following questions. Question 1: A. canoeing B. career C. canal D. caring Question 2: A. fasten B. often C. digest D. castle Question 3: A. non−existent B. none C. nonsense D. gross II. Mark the letter A, B, C, D on your answer sheet to indicate the word that differs from the other three in the position of the primary in each of the following questions. Question 4: A. Christianity B. centenarian C. eradicated D. economic Question 5: A. pioneer B. committee C. precision D. gorilla III. Mark the letter A, B, C, D on your answer sheet to indicate the correct answer to each of the following questions. Question 6: You saved my life. I thank you from the ____ of my heart. A. centre B. bottom C. depths D. top Question 7: Did you have an argument with Francis?” “If you had been there, you ____ the same.” A. did B. would have done C. had done D. would be Question 8: If orders keep coming in like this, I‟ll have to ____ more staff. A. give up B. add in C. gain on D. take on Question 9: He couldn‟t rest or sleep because ____ too much coffee. A. drinking B. been drinking C. had been drinking D. he had been drinking Question 10: There is a very clear relationship ____ education and academic success. A. about B. between C. for D. in Question 11: Everyone should travel; it really ____ the mind. A. broadens B. develops C. opens D. widens Question 12: Many people believe that violent computer games can have a harmful ____ on children. A. affect B. effect C. damage D. involvement Question 13: Navigation around the globe is a lot simpler thanks to the information we receive from ____. A. satellites B. stations C. systems D. shuttles Question 14: What do you think ____ me? A. told B. they told C. didn‟t tell D. did he tell Question 15: When you do something, you should _________. A. weigh up the pros and cons B. get through to C. turn over a new leaf D. go down well with Question 16: Something ____ happened or they would be here by now. A. must B. must be C. must have D. must have been Question 17: We were told to put it where it was usually ____. A. belonged B. fit C. had D. stored Question 18: A demonstration is an act of showing by giving proof or ____evidence. A. a B. an C. the D. Ø A. a B. an C. the D. Ø Fanpage : Đề Thi Thử THPT Quốc Gia Tài Liệu Ôn Thi http:facebook.comdethithu.net KÌ THI THỬ LẦN 1 CHUẨN BỊ CHO KÌ THI THPT QUỐC GIA Môn thi: TIẾNG ANH Thời gian làm bài: 90 phút Website: http:dethithu.net www.DeThiThu.Net DeThiThu.Net www.DeThiThu.Net DeThiThu.NetQuestion 19: She liked to say that she was just one of his ____ happy customers. A. all B. lots of C. many D. some Question 20: I asked Meg earlier if she thought it would rain and she said “I ____.” A. hope B. hope it C. hope not D. don‟t hope so Question 21: I‟m ____ a swimmer as my sister. A. better B. good as C. not as good D. so good Question 22: We decided to ____ in Athens for a few days on our way home. A. stop over B. put up C. set up D. close down Question 23: Some of the girls in my group tease me because I don‟t wear makeup but I don‟t ____. A. wear B. care C. do D. like Question 24: There is no point in trying to warn him of the danger. He will just ____ a deaf car. A. show B. turn C. give D. offer IV. Mark the letter A, B, C, D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions. Question 25: Prior to World War I, 20 percent of American homes had electricity. A. Before B. During C. After D. Despite Question 26: The flowering pebble is a plant that looks like a stone and grows in arid areas. A. deserted B. damp C. dry D. barren V. Mark the letter A, B, C, D to indicate the word(s) SIMILAR in meaning to the underlined word(s) in each of the following questions. Question 27: Originally developed for Southern California, the Richter Scale was expanded for worldwide use. A. prolonged B. enlarged C. minuscule D. swamped Question 28: The jute, a relative of the basswood trees, flourishes in warm humid climates. A. amplifies B. swells C. thrives D. prolongs Question 29: Excessive amounts of lead in the air can decrease a child‟s intelligence. A. boom B. diminish C. abate D. swamp VI. Mark the letter A, B, C, D on your answer sheet to indicate the underlined part that needs correction in each of the following questions. Question 30: Playing jokes on April Fool‟s Day is common in many regions, although noneknows how the tradition began. A. jokes on B. none C. knows how D. began Question 31: Farmers in all parts of Asia own their own farms, but tenant farmers are also practiced. A. Farmers B. own C. own farms D. farmers are Question 32: Japanese initially usedjeweled objects to decorate swords and ceremonial items. A. Japanese B. used C. jeweled D. decorate Question 33: Because of attitudes shape behavior, psychologists want to find out how opinions arc formed. A. Because of B. shape C. psychologists D. are formed Question 34: As the roles of people in society change, so does the rules of conduct in certain situations. A. As the roles B. so does C. rules of D. situations VII. Read the following passage and mark the letter A, B, C, D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks. Denmark Denmark is the smallest and most southerly of the countries of Scandinavia. (35) ____ lie in northern Europe. It is probably best (36) ____ for being home to the powerful Vikings, (37) ____ 1,000 years ago. Denmark is a small country, with limited natural (38) ____. Nevertheless, it has become one of the richest countries in the (39) ____. Denmark has its own (40) ____ culture and traditions, and a tongue−twisting language, which includes several different dialects. Although Denmark is a member (41) ____ the European Union, recently it has been reluctant to work more closely with the EU and give up (42) ____ of its independence. DeThiThu.Net DeThiThu.NetWealth in Denmark is shared out more evenly than in most countries, because people pay high taxes. Many workers pay more than 50 percent of their wages in tax. The money is used to pay (43)____ a welfare system which includes health care, benefits for the unemployed and the elderly, and public services. Compared to the rest of the world, it is (44) ____ to become either very rich or very poor in Denmark. Question 35: ________(35) A. whose B. when C. which D. where Question 36: ________(36) A. liked B. known C. seen D. heard Question 37: ________(37) A. over B. more C. since D. less Question 38: ________(38) A. resources B. features C. natures D. sources Question 39: ________(39) A. earth B. land C. space D. world Question 40: ________(40) A. distant B. distinctive C. disliked D. disinterested Question 41: ________(41) A. from B. to C. in D. of Question 42: ________(42) A. many B. every C. very D. some Question 43: ________(43) A. at B. for C. on D. to Question 44: ________(44) A. impossible B. simple C. difficult D. easy VIII. Read the following passage and mark the letter A, B, C, D on your answer sheet to indicate the correct answer to each of the questions . Arthur Dove Arthur Dove was an abstract nature painter whose work was radically different and underappreciated in the American art scene. 1 In fact, Dove was the first American artist to paint in an entirely abstract manner. 2 He painted a set of six abstract works around 1910, prior to the European artist Wassily Kandinsky‟s famous abstract compositions. 3 Kandinsky‟s abstract work, however, complemented the cultural context in Europe, and was therefore appreciated. Dove‟s work had no similar cultural context in America. 4 Overall, Doves abstract paintings did nothing to change Amercican art. His work was not once but twice orphaned: by the general indifference of the Amercican public, and by his own reclusive nature. Nevertheless, Doves abstract paintings remain interesting compositions on nature. Dove once wrote, “I would like to make something that is real in itself, or to be real without looking like something else, that does not remind anyone of any other thing, and that does not have to be explained, like the letter A for instance.” Question 45: What is the main purpose of this passage? A. to discuss the effects of Dove‟s work on Europe B. to compare the works of Dove and Kandinsky C. to explain why Dove‟s work is famous D. to explain why Dove‟s paintings did not change the American art scene Question 46: According to the passage, why weren‟t Dove‟s works noticed? A. Because there were too many abstract nature painters at the time. B. Because his paintings did nothing to change society. C. Because they did not have a cultural context in America. D. Because America was not interested in European painters. Question 47: The word orphaned in the passage is closest in meaning to ____. A. criticized B. ignored C. valued D. destroyed Question 48: According to the passage, which of the following is not true about Dove and Kandinsky? DeThiThu.Net DeThiThu.Net DeThiThu.Net DeThiThu.NetA. One was popular, while the other not. B. They were both European painters. C. Their works were somewhat similar. D. They were boih abstract artists. Question 49: The word indịfference in the passage is the opposite of ____. A. dislike B. interest C. joy D. ignorance Question 50: Which of the following can be inferred from the reading? A. Dove gave up painting because the American public did not care. B. Dove„s work is more appreciated today than when it first appeared. C. Dove did not have support from European artists. D. Dove‟s unsuccessful exhibition led him to change his style. Question 51: Which is the best place for the following sentence? “This, however, did not make him famous.” A. 1 B. 2 C. 3 D. 4 Question 52: The word “reclusive in the passage is closest in meaning to ____ . A. charming B. sociable C. shy D. generous Question 53: Which of the following best expresses the meaning of the quotation? A. Dove wanted to create works of art that were absolutely unique. B. Dove wanted people to “read” his paintings as if they were letters. C. Dove wanted his art to remind people of other artists‟ work. D. Dove wanted to create art that was difficult to explain. Question 54: The paragraph following the passage world most probably be _____. A. a discussion of why Dove‟s work was orphaned B. a discussion of the European art scene C. a discussion of the differences between the works of Dove and Kandinsky D. a discussion of Dove‟s best paintings IX. Read the following passage and mark the letter A, B, C, D on your answer sheet to indicate the correct answer to each of the questions . Television An American TV network has had an international hit with the drama 24”. a thriller known for its suspense and often graphic violence. Over the past year, controversy has surrounded the series because of its portrayal of Muslim terrorists and its frequent scenes of torture. But the content of “24” is not the only thing that would have been unthinkable on prime−time television 20 years ago. Its form also represents a major change in modem TV: during each episode‟s 44 minutes − a real−time hour, minus 16 minutes for commercials – the show connects the lives of 21 different characters, each with their own personalities and specific relationships with other characters. Nine different story lines (or “threads) arc depicted, each involving events and information revealed in previous episodes. I 2 For years many people have assumed that popular culture is in a state of decline rapidly degenerating into “junk culture with no worthwhile purpose. But an interesting new book challenges that assumption. “Everything Bad is Good for You: How Today‟s Popular Culture Is Actually Making Us Smarter, by Steven Johnson, makes a persuasive argument that today‟s complex TV dramas and other pop culture Products gives healthy mental exercise. He calls the use or complex, interwoven plot lines involving multiple characters “multi−threading”, and it is a new and growing phenomenon in TV To keep up with shows like “24, he points out, you must “pay attention, make inferences, track shifting social relationships, and these cognitive challenges are changịng our mental development for the better. 3 4 The most obvious change in the last five years of narrative entertainment is the rise of reality TV, Surely, you might be thinking, watching “Survivor or “The Bachelor” cannot possibly raise anyones IQ “Survivor” is now in its tenth season, and “The Bachelor” is in its seventh. But as Johnson tells us lately “even the junk has improved”. The new reality shows are like games: they arc series of competitive tests, each more challenging than the last, and with rules that must be learned as you play. On “Survivor for instance, the participants and the audience know the general objective of the game but each episode brings new challenges that require quick thinking. Success in these games calls for the intellectual labor of finding the weak spots in the rules and in your opponents. This labor is done not just by the stars of the shows but the viewers at home as well. This is what makes these shows such fun to watch − the human mind enjoys being challenged. As Johnson writes, “There‟s real pleasure ... in solving puzzles, detectingpatterns or understanding a complex narrative system. DeThiThu.NetQuestion 55: What is the topic of the passage? A. The decline of TV today B. Benefits of TV today C. TV and culture D. Why “24” became a hit Question 56: Which is the best place for the following sentence? “It is not only hour−long dramas that make us smarter. A. l B. 2 C. 3 D. 4 Question 57: The word “each” in paragraph I refers to ____. . A. story lines B. characters C. episodes D. personalities Question 58: The author begins the passage by discussing “24” in order to ____. A. prove that TV has become much more violent B. show how TV has become more complex C. explain why many TV shows nowadays are controversial D. argue against ỈIS graphic violence and portrayal of terrorists Question 59: It can be inferred that the author of the passage A. agrees with Steven Johnson‟s views B. strongly disagrees with Steven Johnsons views C. has no opinion about Steven Johnson‟s views D. agrees with some of Johnson‟s views but disagrees with others Question 60: According to the passage, Johnson‟s book argues all following except that ____. A. popular culture is not in decline B. many TV shows involve cognitive challenges C. people enjoy the effort of understanding complex shows D. hour−long dramas bring the greatest benefits Question 61: Multi−threading in TV is a new type of ____. . A. form B. content C. series D. character Question 62: The author mentions junk culture” in paragraph 2 in order to ____ . A. emphasize how worthless most TV shows are B. contrast a common view of TV with the one he presents in the passage C. explain why TV viewing is in decline in the United States D. argue against the view that popular culture can be worthwhile Question 63: The word “they in paragraph 3 refers to ____. A. junk B. shows C. games D. “Joe Millionaire” and The Bachelor” Question 64: The word detecting in paragraph 3 is closest in meaning to ____ . A. making B. admiring C. remembering D. finding Part II. Complete the second sentence so that it has a similar meaning to the first sentence. Question65: Students may not park here. Students are. ....................................................................................................................................... Question66: We‟ve written fifty per cent of the report already. Half . .................................................................................................................................................... Question67: She didn‟t escape injury; she wasnt wearing a crash helmet. If only ................................................................................................................................................. Question68: Amy was bitten by a dog when she was very young and she still remembers it. Amy still remembers . ......................................................................................................................... Question69: “I shall return the day after tomorrow. His only comment . ............................................................................................................................. In about 140 words, write a paragraph about benefits of physical exercises ĐÁP ÁN VÀ LỜI GIẢI CHI TIẾT 1.D 2.C 3.B 4.C 5.A 6.B 7.B 8.D 9.D 10.B 11.A 12.B 13.A 14.B 15.A 16.C 17.D 18.D 19.C 20.C 21.C 22.A 23.B 24.B 25.C 26.B 27.B 28.C 29.B 30.B DeThiThu.Net Question69: “I shall return the day after tomorrow. Hi s only comment . ............................................................................................................................. Đề Luận : An about 140 words, write a paragraph about benefits of physical exercises DeThiThu.Net31.D 32.A 33.A 34.B 35.C 36.B 37.A 38.A 39.D 40.B 41.D 42.D 43.B 44.C 45.D 46.C 47.B 48.B 49.B 50.B 51.C 52.C 53.A 54.D 55.B 56.D 57.A 58.B 59.D 60.D 61.A 62.B 63.C 64.D Question 1. Đáp án D Đáp án là D. Từ caring có phần gạch chân được phát âm là eə, các từ còn lại có phần gạch chân được phát âm là ə Question 2. Đáp án C Đáp án là C. Từ digest có phần gạch chân được phát âm là t, các từ còn lại có phần gạch chân không được phát âm Question 3. Đáp án B Đáp án là B. Từ none có phần gạch chân được phát âm là ʌ, các từ còn lại có phần gạch chân được phát âm là ɒ Question 4. Đáp án C Đáp án là C. Từ eradicate nhấn âm tiết thứ hai, các từ còn lại nhấn âm thứ ba. Question 5. Đáp án A Đáp án là A. Từ pioneer nhấn âm tiết thứ ba, các từ còn lại nhấn âm thứ hai. Question 6. Đáp án B Đáp án là B. from the bottom of one‟s heart: tận đáy lòng .. Question 7. Đáp án B Đáp án là B. Câu điều kiện loại III: If + S + had + PII, S + would + have + PII. Question 8. Đáp án D Đáp án là D. take on: Nhận vào làm, thuê, mướn (người làm...) Các cụm còn lại: give up: từ bỏ, add in: thêm vào; gain on: Tranh thủ được lòng (ai) Question 9. Đáp án D Dễ dàng nhận thấy, because + clause → chỉ đáp án D là chấp nhận được Dịch: Anh ta không thể nghỉ ngơi hay ngủ được bởi vì anh ta đã uống quá nhiều café. Question 10. Đáp án B Đáp án là B. between …. and …..: giữa ….. và …. Question 11. Đáp án A Đáp án là A. Broaden the mind – mở rộng hiểu biết Question 12. Đáp án B Đáp án là B. Cấu trúc: have a effect on …: có ảnh hưởng đến….. Question 13. Đáp án A Đáp án là A. satellites: vệ tinh Các từ còn lại: station: trạm, bến; system: hệ thống; shuttles: hê thống giao thông vận tải tuyến đường ngắn. Question 14. Đáp án B S+ think (+ that) +clause → câu thiếu chủ ngữ và động từ trong mệnh đề sau “think”. → đáp án phù hợp nhất là B. Question 15. Đáp án A Đáp án là A. weigh up the pros and cons: cân nhắc thuận lợi và bất lợi Nghĩa các cụm còn lại: get through to st: đạt được một bậc cao hơn trong cuộc thi đấu get through to sb: nối máy được với ai turn over a new leaf: cải tà quy chính Question 16. Đáp án C Đáp án là C.must have done: dùng để diễn tả hành động sự việc chắc chắn đã xảy ra trong quá khứ, thường là có cơ sở. Dịch: Có thứ gì đó đã xảy ra hoặc họ sẽ đến đây ngay bây giờ. DeThiThu.NetQuestion 17. Đáp án D Đáp án là D. stored: được bảo quản, lưu trữ Dịch: Chúng tôi được bảo là để nó vào nơi mà nó được bảo quản bình thường. Các từ còn lại: belong to: thuộc về; fit: vừa vặn, hợp; Question 18. Đáp án D Đáp án là D. evidence: bằng chứng → danh từ không đếm được→ A và B loại. Trường hợp này cũng không dùng “the”, theo cấu trúc song song khi dùng liên từ “or”, proof không dùng “the” → evidence cũng không dùng”the” Question 19. Đáp án C Đáp án là C. one of his many happy customers: một trong những khách hàng vui vẻ của anh ta. Xét về hợp nghĩa không chọn A và D được . all : tất cả; some: một vài Xét về hình thức, B cũng không chọn được vì không ai dùng “one of his lots of ... Question 20. Đáp án C Cấu trúc thể hiện sự đồng tình “ I hope so.”, cấu trúc thể hiện sự không đồng tình “I hope not.” → Đáp án là C. Question 21. Đáp án C Đáp án là C. Cấu trúc so sánh ngang bằng: S + be + as + adj + aan + N + as + O. Phủ định thêm “not” vào sau “be” Question 22. Đáp án A Đáp án là A. stop over: ngừng lại ( trong một cuộc đi ) Các cụm vong lại: put up:đăt lên; set up:dựng lên; close down: đóng cửa hẳn ( không buôn bán, sản xuất ) Question 23. Đáp án B Đáp án là B. “ I don‟t care.” – Tôi không quan tâm. Question 24. Đáp án B Đáp án là B. Cấu trúc: Turn a deaf ear: từ chối lắng nghe hay đáp lời một tuyên bố hay yêu cầu Question 25. Đáp án C Đáp án là C. Prior to = Before: trước khi >< After: Sau khi During: trong, trong suốt ( quá trình ) … , Despite: mặc dù Question 26. Đáp án B Đáp án là B. arid: khô cằn ( đất ) >< damp: ẩm, ẩm ướt Các từ còn lại: deserted: hoang vắng, hiu quạnh; dry: khô, barren: cằn cỗi ( đất ) Question 27. Đáp án B Đáp án là B. expanded = enlarged: được mở rộng Các từ còn lại: prolonged: được kéo dài ra; minuscule: nhỏ xíu, rất nhỏ; swamped: bị ngập ( nước ) Question 28. Đáp án C Đáp án là C. flourish: mọc sum suê ( cây ) = thrive: lớn nhanh, phát triển mạnh Các từ còn lại: amplify: mở rộng; swell: làm phình to lên; prolong: kéo dài ra Question 29. Đáp án B Đáp án là B. decrease = diminish: làm giảm bớt Các từ còn lại: boom: âm vang; abate: làm dịu đi, làm giảm bớt ( nỗi đau, cơn đau ); swamp: làm nhập nước Question 30. Đáp án B Đáp án là B. none → no one Question 31. Đáp án D Đáp án là D. farmers are → farming is. Question 32. Đáp án A Đáp án là A. Japanese → The Japanese Question 33. Đáp án A Đáp án là A. Because of → Because Question 34. Đáp án B Đáp án là B. so does → so do Question 35. Đáp án C Đáp án là C. which: đại từ quan hệ thay thế cho “ Scandinavia” Question 36. Đáp án B DeThiThu.NetĐáp án là B. best−known hình thức so sánh hơn nhất của well known. Be well known for: nổi tiếng về … Question 37. Đáp án A Đáp án là A. over 1,000 years ago: trên một nghìn năm trước. Ta có, overunder + số đếm: trên dưới …. Question 38. Đáp án A Đáp án là A. natural resources: tài nguyên thiên nhiên Các từ còn lại: features: những đặc điểm; nature: tự nhiên, bản chất ( không có dạng số nhiều ); sources: các nguồn Question 39. Đáp án D Đáp án là D. in the world: trên thế giới Các từ còn lại: earth: trái đất,land: đất liền; space: không gian Question 40. Đáp án B Đáp án là B. own distinctive culture and traditions: nền văn hóa và truyền thống đặc biệt riêng Các từ còn lại: distant: xa trong không gian và thời gian; disliked: không được yêu thích; disinterested: không vụ lợi Question 41. Đáp án D Đáp án là D. a member of the European Union: một thành viên của Liên minh châu Âu Question 42. Đáp án D Dùng phương pháp loại trừ: Every và very không có cấu trúc theo sau là giới từ of. Many + of + Ns, nhưng “independence” là danh từ không đếm được → Đáp án là D. some of + ..Ns N( uncountable ) Question 43. Đáp án B Đáp án là B. pay for: trả ( tiền ) cho. … Question 44. Đáp án C Dựa vào nghĩa chọn đáp án là C. difficult: khó Các từ còn lại : impossible: không thể; simple: đơn giản, easy: dễ Question 45. Đáp án D Đáp án là D. Giải thích tại sao những bức vẽ của Dove không thay đổi được viễn cảnh nền nghệ thuật nước Mỹ Một số lý do đề cập: − Dove‟s work had no similar cultural context in America.. − His work was not once but twice orphaned: by the general indifference of the Amercican public, and by his own reclusive nature. Question 46. Đáp án C Đáp án là C. Ý trong bài so sánh giữa tác phẩm được đề cao của Kandinsky và Dove: Kandinsky‟s abstract work, however, complemented the cultural context in Europe, and was therefore appreciated. Dove‟s work had no similar cultural context in America. Question 47. Đáp án B Đáp án là B. orphaned = ignored: bị bỏ qua, không được để ý đến Các từ còn lại: criticized: bị phê bình; valued: được coi trọng; destroyed: bị phá hủy Question 48. Đáp án B Đáp án là B. Ý trong bài cho thấy Dove là người Mỹ, còn Kandinsky là người châu Âu : In fact, Dove was the first American artist to paint in an entirely abstract manner. He painted a set of six abstract works around 1910, prior to the European artist Wassily Kandinsky‟s famous abstract compositions. Question 49. Đáp án B Đáp án là B. indịfference : thờ ơ, không quan tâm >< interest: quan tâm, Các từ còn lại dislike: không thích; joy: niềm vui; ignorance: sự lờ đi, không để ý đến. Question 50. Đáp án B Đáp án là B. Có thể thấy, đoạn 2 nói về sự khởi đầu không tốt của Dove, nhưng đoạn 2, các tác phẩm của ông nhận được sự quan tâm hơn, dựa vào câu: Doves abstract paintings remain interesting compositions on nature. Question 51. Đáp án C This, however, did not make him famous. −Điều này, tuy nhiên, đã không làm cho ông nổi tiếng. → Đáp án là C. 2 He painted a set of six abstract works around 1910, prior to the European artist Wassily Kandinsky‟s DeThiThu.Netfamous abstract compositions. −Ông đã vẽ một bộ sáu tác phẩm trừu tượng khoảng năm 1910, trước những tác phẩm trừu tượng nổi tiếng của họa sĩ châu Âu Wassily Kandinsky. Question 52. Đáp án C Đáp án là C, reclusive = shy: bẽn lẽn, rụt rè Các từ còn lại: charming:duyên dáng; sociable: thân thiện; generous: hào phóng Question 53. Đáp án A Câu nói của Dove: Tôi muốn làm một cái gì đó là có thật trong chính nó, hoặc là thực mà không giống như cái gì khác, điều đó không làm cho bất cứ ai nhớ hoặc biết về bất kỳ điều khác, và điều đó không phải được giải thích, giống như chữ A chẳng hạn. → Đáp án là A. Dove muốn tạo ra tác phẩm nghệ thuật mà là hoàn toàn độc đáo. Question 54. Đáp án D Đoạn văn đã đề cập đến lý do tại tác phẩm không được đề cao trong những giai đoạn đầu của nghệ thuật vẽ tranh trừu tượng. → Có thể suy ra, đoạn văn tiếp theo sẽ nói về những bức vẽ thành công nhất của Dove → Đáp án là D. A. thảo luận về lý do tại sao tác phẩm của Dove bị lờ đi → trong bài đã đề cập B. Thảo luận về cảnh nghệ thuật châu Âu → cái này không bám sát tới Dove. C. Thảo luận về sự khác nhau giữa các tác phẩm của Dove và Kandinsky → ý này cũng đã được đề cập. Question 55. Đáp án B Đáp án là B. Những lợi ích của TV ngày hôm nay. Có thể thấy, đoạn văn liệt kê một số chương trình và lợi ích của nó. Ví dụ: − .. today‟s complex TV dramas and other pop culture Products gives healthy mental exercise. − ….This is what makes these shows such fun to watch − the human mind enjoys being challenged. Question 56. Đáp án D Đáp án là D. Ý thể hiện: you might be thinking, watching “Survivor or “The Bachelor” cannot possibly raise anyones IQ “Survivor” is now in its tenth season, and “The Bachelor” is in its seventh. But as Johnson tells us lately “even the junk has improved”…. Question 57. Đáp án A Đáp án là A. Nine different story lines (or “threads) arc depicted, eachinvolving events and information revealed in previous episodes. Question 58. Đáp án B Đáp án là B. Đoạn văn nói về “24” để nói về sự phức tạp của TV, thể hiện ở chi tiết: Its form also represents a major change in modem TV: during each episode‟s 44 minutes − a real−time hour, minus 16 minutes for commercials – the show connects the lives of 21 different characters, …. each involving events and information revealed in previous episodes Question 59. Đáp án D Đáp án là D. Tác giả đồng tình với một số quan điểm của Johnson, nhưng không phải tất cả đươc thể hiện ở đoạn 2 và 3. Question 60. Đáp án D Đáp án là D. A được đề cập: .. popular culture is in a state of decline rapidly B được đề cập: these cognitive challenges are changing our mental development for the better. C được đề cập: the participants and the audience know the general objective of the game but each episode brings new challenges that require quick thinking… This is what makes these shows such fun to watch − the human mind enjoys being challenged. Question 61. Đáp án A Đáp án là A. Ý trong bài: … interwoven plot lines involving multiple characters “multi−threading” Question 62. Đáp án B Đáp án là B. Ý thể hiện sự tương phản qua từ “but”: For years many people have assumed that popular culture is in a state of decline rapidly degenerating into “junk culture with no worthwhile purpose. But an interesting new book challenges that assumption…. Question 63. Đáp án C DeThiThu.Net DeThiThu.NetĐáp án là C. Ý trong bài: The new reality shows are like games: they are series of competitive tests, each more challenging than the last, and with rules that must be learned as you play. Question 64. Đáp án D Đáp án là D. detecting: tìm ra, khám phá ra = finding Các từ còn lại: making: làm; admiring: khâm phục; remembering: nhớ Question 65. Students are not allowed permitted to park here. Question 66. Half of the report has been written already. Question 67. If only she had been wearing had worn a cash helmet, she would might could have escaped injury. Question 68. Amy still remembers being bitten by a dog when she was very young. Question 69. His only comment was that he would return in two days time. Question 70. Nobody can deny the benefits of sports and physical exercises. In fact, such sports as: swimming, jogging, jumping, playing tennis, football, basket − ball, volley − ball, skating, skiing etc bring us a well − proportioned body. When we practise a certain sport, our muscles are developed; blood circulates easily in blood vessels therefore well have a good appetite and a sound sleep As for me, my favourite sport is jogging in the morning and playing tennis in the afternoon. By practicing these sports regularly I always feel fit and never get sick. Health is much more precious than money. We cant lead a happy life if we are continually tortured by diseases. Try to keep a clear mind in a healthy body and get accustomed to regular practice of certain sports, well feel life worth living. Truy cập http:dethithu.net mỗi ngày để tải các đề thi thử THPT Quốc Gia ( Đại Học ) các môn TOÁN – ANH – VĂN – LÝ – HÓA – SINH mới nhất,nhanh nhất từ các trường THPT và trung tâm luyện thi đại học trong nước.Chúng tôi luôn cập nhật đề thi thử mỗi ngày vậy nên các bạn yên,luôn có các đề thi thử mới nhất để các bạn tham khảo. Tham gia nhóm : ÔN THI ĐH TOÁN – ANH trên Facebook để cùng hỏi đáp, học tập : http:facebook.comgroupsonthidhtoananhvan DeThiThu.Net DeThiThu.Net Fanpage của chúng tôi.Like để cập nhật nhiều đề thi thử,tài liệu ôn thi mới nhất Fanpage: Đề Thi Thử THPT Quốc Gia Tài Liệu Ôn Thi :
Xem thêm

25 Đọc thêm