The identification of mental load has important practical significance for human life. In recent years, studies have used physiological signals of different modalities to measure mental load. However, there is no single indicator that can fully assess mental load, and the fusion of multimodal signals to measure this variable is still controversial. The emergence of simultaneous EEG and fMRI enables researchers to explore brain function, especially working memory, with high temporal and spatial resolution. In this study, we fused EEG and fMRI data on network features to estimate working memory load. By introducing a filter bank, the phase synchronization values covering the full frequency band were extracted as the EEG network features. Then, we proposed the Wasserstein distance to measure functional connectivity in single-trial fMRI data. Finally, Fisher vector was used to fuse these features from the above two modalities, and this method was compared with the direct splicing features. The results showed that the Fisher vector was more effective for recognition than direct splicing was, providing a new option for multimodality feature fusion. In addition, distance-based functional connectivity extraction on the individual level enriches the range of tools with which to study brain network.
Multivariate classification techniques have been widely applied to decode brain states using functional magnetic resonance imaging (fMRI). Because the number of labeled samples is limited by the financial and safety consideration during fMRI data acquirement, it is not easy to train a robust classifier for fMRI data. Recently, semi-supervised learning has been proposed to train the classifier using both labeled training data and unlabeled data. Moreover, sparse representation based classification (SRC) has seldom been applied to fMRI data, although it exhibits a state-of-the-art classification performance in image processing. In this study, we proposed semi-supervised SRC with random sample subset ensemble strategy (semiSRC-RSSE) that used the average of class-specific coefficients as the SRC classification criterion and dynamically update the training dataset using the random sample subset ensemble method to measure the confidence of the prediction of each test sample. The results of the simulated and real fMRI experiments showed that semiSRC-RSSE method largely improved the classification accuracy of SRC and had better performance than support vector machine (SVM) and semi-supervised SVM with the random sample subset ensemble strategy (semiSVM-RSSE).
Recent advances in functional magnetic resonance imaging (fMRI) techniques and machine learning have shown that it is possible to decode distinct brain state from complex brain activities, which have raised widespread concern. Deep learning is a popular method of machine learning and has achieved remarkable results in the field of speech recognition, image recognition and so on. However, there are many challenges in medical image analysis when using deep learning. Aiming to solve the difficulty of subject-transfer decoding, high dimensional feature extraction and slow computation, here we proposed a deep convolutional decoding (DCD) model. First, an architecture of deep convolutional network became a subject-transfer feature extractor on task-fMRI (tfMRI) data. Then, the high dimensional abstract feature was used to identify certain brain cognitive state. The experimental results show that our proposed method can achieve higher decoding accuracy of brain state across different subjects compared with traditional methods.
Leukoaraiosis (LA) describes diffuse white matter abnormalities on CT or MR brain scans, often seen in the normal elderly and in association with vascular risk factors such as hypertension, or in the context of cognitive impairment. The mechanism of cognitive dysfunction is still unclear. The recent clinical studies have revealed that the severity of LA was not corresponding to the cognitive level, and functional connectivity analysis is an appropriate method to detect the relation between LA and cognitive decline. However, existing functional connectivity analyses of LA have been mostly limited to linear associations. In this investigation, a novel measure utilizing the extended maximal information coefficient (eMIC) was applied to construct non-linear functional connectivity in 44 LA subjects (9 dementia, 25 mild cognitive impairment (MCI) and 10 cognitively normal (CN)). The strength of non-linear functional connections for the first 1% of discriminative power increased in MCI compared with CN and dementia, which was opposed to its linear counterpart. Further functional network analysis revealed that the changes of the non-linear and linear connectivity have similar but not completely the same spatial distribution in human brain. In the multivariate pattern analysis with multiple classifiers, the non-linear functional connectivity mostly identified dementia, MCI and CN from LA with a relatively higher accuracy rate than the linear measure. Our findings revealed the non-linear functional connectivity provided useful discriminative power in classification of LA, and the spatial distributed changes between the non-linear and linear measure may indicate the underlying mechanism of cognitive dysfunction in LA.
Neuroimaging studies of working memory training have identified the alteration of brain activity as well as the regional interactions within the functional networks such as central executive network (CEN) and default mode network (DMN). However, how the interaction within and between these multiple networks is modulated by the training remains unclear. In this paper, we examined the interaction of three training-induced brain networks during working memory training based on real-time functional magnetic resonance imaging (rtfMRI). Thirty subjects assigned to the experimental and control group respectively participated in two times training separated by seven days. Three networks including silence network (SN), CEN and DMN were identified by the training data with the calculated function connections within each network. Structural equation modeling (SEM) approach was used to construct the directional connectivity patterns. The results showed that the causal influences from the percent signal changes of target ROI to the SN were positively changed in both two groups, as well as the causal influence from the SN to CEN was positively changed in experimental group but negatively changed in control group from the SN to DMN. Further correlation analysis of the changes in each network with the behavioral improvements showed that the changes in SN were stronger positively correlated with the behavioral improvement of letter memory task. These findings indicated that the SN was not only a switch between the target ROI and the other networks in the feedback training but also an essential factor to the behavioral improvement.
The functional magnetic resonance imaging (fMRI) researches on working memory have found that activation of cortical areas appeared dependent on memory load, and event-related potentials (ERP) studies have demonstrated that amplitudes of P300 decreased significantly when working memory load increased. However, the cortical activities related with P300 amplitudes under different memory loads remains unclear. Joint fMRI and EEG analysis which fusions the time and spatial information in simultaneous EEG-fMRI recording can reveal the regional activation at each ERP time point. In this paper, we first used wavelet transform to obtain the single-trial amplitudes of P300 caused by a digital N-back task in the simultaneous EEG-fMRI recording as the ERP feature sequences. Then the feature sequences in 1-back condition and 3-back condition were introduced into general linear model (GLM) separately as parametric modulations to compare the cortical activation under different memory loads. The results showed that the average amplitudes of P300 in 3-back significantly decreased than that in 1-back, and the activities induced by ERP feature sequences in 3-back also significantly decreased than that in the 1-back, including the insular, anterior cingulate cortex, right inferior frontal gyrus, and medial frontal gyrus, which were relevant to the storage, monitoring, and manipulation of information in working memory task. Moreover, the difference in the activation caused by ERP feature showed a positive correlation with the difference in behavioral performance. These findings demonstrated the locations of P300 amplitudes differences modulated by the memory load and its relationship with the behavioral performance.
KEYWORDS: Functional magnetic resonance imaging, Data modeling, Visualization, Brain, Feature selection, Visual process modeling, Neuroimaging, Computer simulations, Monte Carlo methods, Information visualization
Recently, sparse algorithms, such as Sparse Multinomial Logistic Regression (SMLR), have been successfully applied in decoding visual information from functional magnetic resonance imaging (fMRI) data, where the contrast of visual stimuli was predicted by a classifier. The contrast classifier combined brain activities of voxels with sparse weights. For sparse algorithms, the goal is to learn a classifier whose weights distributed as sparse as possible by introducing some prior belief about the weights. There are two ways to introduce a sparse prior constraints for weights: the Automatic Relevance Determination (ARD-SMLR) and Laplace prior (LAP-SMLR). In this paper, we presented comparison results between the ARD-SMLR and LAP-SMLR models in computational time, classification accuracy and voxel selection. Results showed that, for fMRI data, no significant difference was found in classification accuracy between these two methods when voxels in V1 were chosen as input features (totally 1017 voxels). As for computation time, LAP-SMLR was superior to ARD-SMLR; the survived voxels for ARD-SMLR was less than LAP-SMLR. Using simulation data, we confirmed the classification performance for the two SMLR models was sensitive to the sparsity of the initial features, when the ratio of relevant features to the initial features was larger than 0.01, ARD-SMLR outperformed LAP-SMLR; otherwise, LAP-SMLR outperformed LAP-SMLR. Simulation data showed ARD-SMLR was more efficient in selecting relevant features.
Alzheimer’s disease (AD) is a progressive neurodegenerative disease with the clinical symptom of the continuous deterioration of cognitive and memory functions. Multiple diffusion tensor imaging (DTI) indices such as fractional anisotropy (FA) and mean diffusivity (MD) can successfully explain the white matter damages in AD patients. However, most studies focused on the univariate measures (voxel-based analysis) to examine the differences between AD patients and normal controls (NCs). In this investigation, we applied a multivariate independent component analysis (ICA) to investigate the white matter covariances based on FA measurement from DTI data in 35 AD patients and 45 NCs from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. We found that six independent components (ICs) showed significant FA reductions in white matter covariances in AD compared with NC, including the genu and splenium of corpus callosum (IC-1 and IC-2), middle temporal gyral of temporal lobe (IC-3), sub-gyral of frontal lobe (IC-4 and IC-5) and sub-gyral of parietal lobe (IC-6). Our findings revealed covariant white matter loss in AD patients and suggest that the unsupervised data-driven ICA method is effective to explore the changes of FA in AD. This study assists us in understanding the mechanism of white matter covariant reductions in the development of AD.
Many studies have reported that discrete cortical areas in the ventral temporal cortex of humans were correlated with the perception of pictures visual stimuli. Moreover, event-related potentials caused by different kinds of picture stimuli
showed different amplitude levels of N170 which was maximal over occipito-temporal electrode sites. However, the
phenomenon which is mentioned above may be correlated with some local bold signal change, and where is the change happened is still unclear. Recently, research for EEG-fMRI has been widely performed through General Linear Model (GLM) to find the relationship between some feature of the ERP component and the activation of local brain area. In our study, we dealt with the simultaneously recorded EEG-fMRI data of picture stimuli to find the correlation between the change of the N170’s amplitude and the BOLD signal. The amplitudes of the N170 component from the average ERPs of 4 different kinds of picture stimuli were extracted from the EEG data and the activation map for the same stimuli was provided based on the fMRI data. GLM was performed including regressors that could represent the change of the N170’s amplitude. Our result showed that fusiform and occipital gyrus were activated by the parametric design and were overlapped by the activation map of the common fMRI design. Thus we might infer that these regions had relationship with the change of the amplitudes of N170. Our research may contribute to location of the source of N170 and bring a new approach for the parameter design of the fMRI signal in EEG-fMRI analysis.
Motor tasks, in our daily life, could be performed through execution and imagination. The brain response underlying
these movements has been investigated by many studies. Neuroimaging studies have reported that both execution and imagination could activate several brain regions including supplementary motor area (SMA), premotor area (PMA),
primary sensorimotor area (M1/S1), posterior parietal lobe (PPL), striatum, thalamus and cerebellum. These findings
were based on the regional activation, and brain regions have been indicated to functionally interact with each other
when performing tasks. Therefore further investigation in these brain regions with functional connectivity measurements may provide new insights into the neural mechanism of execution and imagination. As a fundamental measurement of functional connectivity, connection strength of graph theory has been used to identify the key nodes of connection and their strength-priorities. Thus, we performed a comparative investigation between execution and imagination tasks with functional magnetic resonance imaging (fMRI), and further explored the key nodes of connection and their strength-priorities based on the results of functional activations. Our results revealed that bilateral SMA, contralateral PMA, thalamus and M1/S1 were involved in both tasks as key nodes of connection. These nodes may play important roles in motor control and motor coordination during execution and imagination. Notably, the strength-priorities of contralateral PMA and thalamus were different between the two tasks. Higher strength-priority was detected in PMA for imagination, implicating that motor planning may be more involved in the imagination task.
Neuroimaging studies have revealed that motor imagery (MI) shared similar neural substrates with motor execution
(ME) though there are some differences in the activation pattern. Most previous studies generally focused on voxel-wise based analysis. However, the congruence and difference in functional brain network relevant to MI and ME task has been rarely investigated. In this study, independent component analysis (ICA) was applied to characterize the functional brain networks underlying MI and ME. Results shows that the brain networks underlying MI and ME shared similar brain regions consisted of supplementary motor area (SMA), contralateral primary sensorimotor area (M1/S1), striatum, bilateral premotor area (PMA), posterior parietal lobule (PPL), and cerebellum. However, the ME task induced stronger activities in SMA-proper, bilateral M1/S1 and cerebellum while the MI task produced greater activities in preSMA, right cerebellum, bilateral PMA, parietal cortex and striatum. These findings are in accordance with the model proposed by Hikosaka (2002) that includes the parietal–prefrontal cortical loops for a spatial sequence and the motor cortical loops for a motor sequence. Moreover, the functional connectivity within the MI/ME-relevant network was evaluated using hierarchical integration that can quantify the total amount of interaction within the network and further assess the information exchanges within/between sub-networks. Results of hierarchical integration further indicate that parietalprefrontal areas contributes more to the integration of MI network than that of ME network while motor cortical areas contributes more to the integration of ME network than that of MI network.
The functional magnetic resonance imaging (fMRI) research on face processing have found that the significant
activation by face stimuli mainly locailized at the occipital temporal lobe especilly the fusiform gyrus. However, fMRI
cannot reflect the face processing as time changes. Event-related potential (ERP) can record electrophysiological
changes induced by neuronal activation in time, but spatial information is not well localized. Fusing fMRI and ERP data can perform that how the fMRI activation changes as time move at each ERP time point. Although most of fuse methods perform to analysis by constraint ERP or fMRI data, joint independent component analysis (jICA) method can equally use the ERP and fMRI data and simultaneously examine electrophysiologic and hemodynamic response. In this paper, we use jICA method to analysis two modalities in common data space in order to examine the dynamics of face stimuli response. The results showed that the ERP component N170 response associated with middle occipital gyrus, fusiform gyrus, inferior occipital gyrus, superior temporal gyrus and parahippocampa gyrus for face. Likewise, for non-face, the N170 component was mainly related to parahippocampa gyrus, middle occipital gyrus and inferior occipital gyrus. Further studying on the correlation of the localized ERP response and corresponding average ERP, it was also concluded that the spatial activations related to N170 response induced by face stimulus located in fusiform gyrus, and that induced by non-face stimulus located in parahippocampa gyrus. From the result, fusing fMRI and ERP data by jICA not only provides the time information on fMRI and the spatial source of ERP component, but also reflects spatiotemporal change during face processing.
Real-time functional magnetic resonance imaging (fMRI) is a useful tool that researchers can monitor and assess
dynamic brain activity in real time and train individuals to actively control over their brain activation by using
neurofeedback. Independent Component Analysis (ICA) is a data-driven method which can recover a set of independent sources from data without using any prior information. Since ICA was firstly proposed to be applied to fMRI data by Mckeown (1998), it has become more and more popular in offline fMRI data analysis. However, ICA was seldom used in real-time fMRI studies due to its large time cost. Although Esposito (2005) proposed a real-time ICA (rtICA) framework by combining FastICA with a sliding-window approach, it was only applied to analyze single-slice data rather than full-brain data and was not stable. The semi-blind rtICA (sb-rtICA) method proposed by Ma (2011) can reduce the computation time and improve stability by adding regularization of certain estimated time course using the experiment paradigm information to rtICA. However, the target independent component (IC) cannot be extracted as the first component in all sliding windows by sb-rtICA, which still adds computation time to some extent. The constrained ICA proposed by Lu (2005) can eliminate the ICA’s indeterminacy on permutation. In this study, we proposed a real-time Constrained Independent Component Analysis (rtCICA) method by combining CICA with the sliding-window technique to improve the performance of rtICA. The basic idea of rtCICA is to induce spatial prior information as constraints into ICA so that the target IC can be always automatically extracted as the first one. Both simulated and real-time fMRI experiments demonstrated that rtCICA outperforms rtICA greatly in the stability and the computational time.
Multi-voxel pattern analysis (MVPA) has been widely used in the object category classification of functional magnetic resonance imaging (fMRI) data. Feature selection is an essential operation in pattern classification. Searchlight, based on information mapping, is one method of feature selection. In contrast with traditional methods based on activation, searchlight has more sensitivity and then provides higher statistical power. In this study, we applied two
different feature selection methods, searchlight and activation, combined with linear support vector machine (SVM)
classifier, to investigate the classification effect in classifying 4-category objects on fMRI data. We found that the
average classification accuracies of searchlight were 0.8095 (house vs. face), 0.7240 (house vs. car), 0.7247 (house vs.
cat), 0.6980 (face vs. car), 0.5982 (face vs. cat) and 0.6860 (car vs. cat). For house vs. car, the average classification
accuracy based on searchlight was better than that based on activation (0.7240 vs. 0.7143). Specially, searchlight method performed better than activation for some subjects. The results showed that object category classification of fMRI data based on information mapping were significantly reliable. Our findings suggest that information mapping can be applied in pattern classification in future work.
Magnetic resonance diffusion tensor imaging (DTI) is a kind of effective measure to do non-invasive investigation on
brain fiber structure at present. Studies of fiber tracking based on DTI showed that there was structural connection of
white matter fiber among the nodes of resting-state functional network, denoting that the connection of white matter was
the basis of gray matter regions in functional network. Nevertheless, relationship between these structure connectivity
regions and functional network has not been clearly indicated. Moreover, research of fMRI found that activation of
default mode network (DMN) in Alzheimer's disease (AD) was significantly descended, especially in hippocampus and
posterior cingulated cortex (PCC). The relationship between this change of DMN activity and structural connection
among functional networks needs further research. In this study, fast marching tractography (FMT) algorithm was
adopted to quantitative calculate fiber connectivity value between regions, and hippocampus and PCC which were two
important regions in DMN related with AD were selected to compute white matter connection region between them in
elderly normal control (NC) and AD patient. The fiber connectivity value was extracted to do the correlation analysis
with activity intensity of DMN. Results showed that, between PCC and hippocampus of NC, there exited region with
significant high connectivity value of white matter fiber whose performance has relatively strong correlation with the
activity of DMN, while there was no significant white matter connection region between them for AD patient which
might be related with reduced network activation in these two regions of AD.
Support Vector Machine (SVM) is an accurate pattern recognition method which has been widely used in functional
MRI (fMRI) data classification. Voxel selection is a very important part in classification. In general, voxel selection is
based on brain regions associated with activation caused by different experiment conditions or stimulations. However,
negative blood oxygenation level-dependent responses (deactivation) which have also been found in humans or animals
contribute to the classification of different cognitive tasks. Different from traditional studies which focused merely on
the activation voxel selection methods, our aim is to investigate the deactivation voxel selection methods in the
classification of fMRI data using SVM. In this study, three different voxel selection methods (deactivation, activation,
the combination of deactivation and activation) are applied to decide which voxel is included in SVM classifier with
linear kernel in classifying 4-category objects on fMRI data. The average accuracies of deactivation classification were
73.36%(house vs. face), 60.34%(house vs. car), 60.94%(house vs. cat), 71.43%(face vs. car), 63.17%(face vs. cat)
and 61.61%(car vs. cat). The classification results of deactivation were significantly above the chance level which
implies the deactivation is informative. The accuracies of combination of activation and deactivation method were close
to that of activation method, and it was even better for some representative subjects. These results suggest deactivation
provides useful information in the object category classification on fMRI data and the method of voxel selection based
on both activation and deactivation will be a significant method in classification in the future.
Autobiographical memory is the ability to recollect past events from one's own life. Both emotional tone and memory
remoteness can influence autobiographical memory retrieval along the time axis of one's life. Although numerous studies
have been performed to investigate brain regions involved in retrieving processes of autobiographical memory, the effect
of emotional tone and memory age on autobiographical memory retrieval remains to be clarified. Moreover, whether the
involvement of hippocampus in consolidation of autobiographical events is time dependent or independent has been
controversial. In this study, we investigated the effect of memory remoteness (factor1: recent and remote) and emotional
valence (factor2: positive and negative) on neural correlates underlying autobiographical memory by using functional
magnetic resonance imaging (fMRI) technique. Although all four conditions activated some common regions known as
"core" regions in autobiographical memory retrieval, there are some other regions showing significantly different
activation for recent versus remote and positive versus negative memories. In particular, we found that bilateral
hippocampal regions were activated in the four conditions regardless of memory remoteness and emotional valence.
Thus, our study confirmed some findings of previous studies and provided further evidence to support the multi-trace
theory which believes that the role of hippocampus involved in autobiographical memory retrieval is time-independent
and permanent in memory consolidation.
KEYWORDS: Brain, Microsoft Foundation Class Library, Functional magnetic resonance imaging, Neuroimaging, Statistical analysis, Magnetic resonance imaging, Brain mapping, Cognitive neuroscience, Cognition, Data processing
Real-time functional magnetic resonance imaging (rtfMRI) can be used to train the subjects to selectively control activity
of specific brain area so as to affect the activation in the target region and even to improve cognition and behavior. So
far, whether brain activity in posterior cingulate cortex (PCC) can be regulated by rtfMRI has not been reported. In the
present study, we aimed at investigating whether real-time regulation of activity in PCC can change the functional
connectivity between PCC and other brain regions. A total of 12 subjects underwent two training runs, each lasts 782s.
During the training, subjects were instructed to down regulate activity in PCC by imagining right hand finger movement
with the sequence of 4-2-3-1-3-4-2 during task and relax as possible as they can during rest. To control for any effects
induced by repeated practice, another 12 subjects in the control group received the same experiment procedure and
instruction except with no feedback during training. Experiment results show that increased functional connectivity of
PCC with medial frontal cortex (MFC) was observed in both groups during the two training runs. However, PCC of the
experimental group is correlated with larger areas in MFC than the control group. Because the positive correlation
between task performance and MFC to PCC connectivity has been demonstrated previously, we infer that the stronger
connectivity between PCC and MFC in the experimental group may suggest that the experimental group with
neurofeedback can more efficiently regulate PCC than the control group without neurofeedback.
Real-time fMRI (rtfMRI) is a new technology which allows human subjects to observe and control their own BOLD
signal change from one or more localized brain regions during scanning. Current rtfMRI-neurofeedback studies mainly
focused on the target region itself without considering other related regions influenced by the real-time feedback.
However, there always exits important directional influence between many of cooperative regions. On the other hand,
rtfMRI based on motor imagery mainly aimed at somatomotor cortex or primary motor area, whereas supplement motor
area (SMA) was a relatively more integrated and pivotal region. In this study, we investigated whether the activities of
SMA can be controlled utilizing different motor imagery strategies, and whether there exists any possible impact on an
unregulated but related region, primary motor cortex (M1). SMA was first localized using overt finger tapping task, the
activities of SMA were feedback to subjects visually on line during each of two subsequent imagery motor movement
sessions. All thirteen healthy participants were found to be able to successfully control their SMA activities by self-fit
imagery strategies which involved no actual motor movements. The activation of right M1 was also found to be
significantly reduced in both intensity and extent with the neurofeedback process targeted at SMA, suggestive that not
only the part of motor cortex activities were influenced under the regulation of a key region SMA, but also the increased
difference between SMA and M1 might reflect the potential learning effect.
KEYWORDS: Independent component analysis, Functional magnetic resonance imaging, Detection and tracking algorithms, Brain, Magnetic resonance imaging, Neuroimaging, Data modeling, Computer simulations, Data analysis, Lutetium
Independent component analysis (ICA) is a data-driven approach that has been widely applied to functional magnetic
resonance imaging (fMRI) data analysis. As an exploratory technique, traditional ICA does not require any prior
information about the sources and the mixing matrix. However, it has been demonstrated that incorporating paradigm
information into the ICA analysis can improve the performance of traditional ICA. In 2005, Calhoun proposed semi-blind
ICA which improved the robustness of Infomax ICA in the presence of noises by regulating the estimated time courses with
paradigm information. Different from the Infomax ICA algorithm, FastICA is able to estimating independent components
one by one. If the target component can be estimated earlier, the FastICA algorithm can be terminated beforehand.
Therefore, the order of the target component is important for FastICA to reduce computational time during one-to-one
hierarchical estimation. In this paper, we proposed semi-blind FastICA by adding regularization of the first estimated time
course using the paradigm information to the FastICA algorithm. We demonstrated the feasibility and effectiveness of our
approach in extracting the task-related component from single-task fMRI datasets of block design. Results of both
simulated and real fMRI data suggest that (1) In contrast to FastICA, the time of extracting the target component by
semi-blind FastICA is largely reduced;(2) Semi-blind FastICA can accurately extract the task-related IC as the first one; (3)
Semi-blind FastICA can estimate more accurate time course of the task-related component than FastICA.
Neural mechanism of auditory-visual speech integration is always a hot study of multi-modal perception. The
articulation conveys speech information that helps detect and disambiguate the auditory speech. As important
characteristic of EEG, oscillations and its synchronization have been applied to cognition research more and more. This
study analyzed the EEG data acquired by unimodal and bimodal stimuli using time frequency and phase synchrony
approach, investigated the oscillatory activities and its synchrony modes behind evoked potential during auditory-visual
integration, in order to reveal the inherent neural integration mechanism under these modes. It was found that beta
activity and its synchronization differences had relationship with gesture N1-P2, which happened in the earlier stage of
speech coding to pronouncing action. Alpha oscillation and its synchronization related with auditory N1-P2 might be mainly responsible for auditory speech process caused by anticipation from gesture to sound feature. The visual gesture changing enhanced the interaction of auditory brain regions. These results provided explanations to the power and connectivity change of event-evoked oscillatory activities which matched ERPs during auditory-visual speech integration.
KEYWORDS: Brain, Functional magnetic resonance imaging, Data modeling, Radon, Neural networks, Neurons, Visualization, Neuroimaging, Visual process modeling, Magnetic resonance imaging
A great deal of current literature regarding functional neuroimaging has elucidated the relationships of neurons
distributed all over the brain. Modern neuroimaging techniques, such as the functional MRI (fMRI), provide a
convenient tool for people to study the correlation among different voxels as well as the spatio-temporal patterns of brain
activity. In this study, we present a computational model using radial basis function neural network (RBF-NN) to predict
the fMRI voxel activation with the activation of other voxels acquired at the same time. The fMRI data from a visual
images stimuli presentation experiment was separated into two sets; one was used to train the model, and the other to
validate the accuracy or generalizability of the model. In the visual stimuli presentation experiment, the subject did
simple one-back-repetition tasks when four categories of stimuli (houses, faces, cars, and cats) were presented. Voxel
sets A and B were selected from fMRI data by two different voxel selection criterion: (1) Voxel set A are those activated
for any kind of object stronger than the other three objects in regions of interest (ROIs) without correction (P=0.001); (2)
Voxel set B are those activated for at least one of the categories of stimuli within the ROIs (FWE correction, P=0.05).
RBF-NN regression models construct the nonlinear relationship between the activation of voxels in A and B. Our test
results showed that RBF-NN can capture the nonlinear relationship existing in neurons and reveal the relationship
between voxel's activation from different brain regions.
N170 is an important neurophysiological index to study the underlying mechanisms of face and object perception. In this
study, we proposed a mean-sensitive spatial filtering (MSF) method for linear transformation of event-related potentials
(ERP) that is sensitive to mean differences between stimuli conditions and applied it to N170 component to extract
category-specific spatio-temporal features contained in EEG. MSF method estimated a set of optimal projecting vectors
according to the spatial distribution patterns of N170 means. Then, we applied these spatial filters to single-trial ERP
data and perform classification on the extracted features. In this way, the presence of a larger negative component in
EEG time courses evoked by faces can be detected robustly in single trial EEG, and hereby we can infer the category of
every presented stimulus from faces and objects. Furthermore, we also successfully extracted the unobvious distinct
spatial patterns between cars and cats with MSF and separated them correctly. Our remarkable and robust classification
performances suggest that MSF works well in extracting stable spatial patterns from N170. Therefore, MSF provides a
promising solution for decoding presented visual information basing on single-trial N170 component.
Gray matter volume and cortical thickness are two indices of concern in brain structure magnetic resonance imaging
research. Gray matter volume reflects mixed-measurement information of cerebral cortex, while cortical thickness
reflects only the information of distance between inner surface and outer surface of cerebral cortex. Using Scaled
Subprofile Modeling based on Principal Component Analysis (SSM_PCA) and Pearson's Correlation Analysis, this
study further provided quantitative comparisons and depicted both global relevance and local relevance to
comprehensively investigate morphometrical abnormalities in cerebral cortex in Alzheimer's disease (AD). Thirteen
patients with AD and thirteen age- and gender-matched healthy controls were included in this study. Results showed that
factor scores from the first 8 principal components accounted for ~53.38% of the total variance for gray matter volume,
and ~50.18% for cortical thickness. Factor scores from the fifth principal component showed significant correlation. In
addition, gray matter voxel-based volume was closely related to cortical thickness alterations in most cortical cortex,
especially, in some typical abnormal brain regions such as insula and the parahippocampal gyrus in AD. These findings
suggest that these two measurements are effective indices for understanding the neuropathology in AD. Studies using
both gray matter volume and cortical thickness can separate the causes of the discrepancy, provide complementary
information and carry out a comprehensive description of the morphological changes of brain structure.
Examining the spontaneous activity to understand the neural mechanism of brain disorders and establish
neuroimaging-based disease-related biomarkers is a focus in recent resting-state functional MRI (fMRI) studies. The
present study hypothesized that resting activity in the default mode network (DMN), which was used for characterizing
the resting-state human brain might be different in patients with depressed Parkinson disease (dPD) compared with
non-depressed Parkinson disease (ndPD) patients. To test the hypothesis, we firstly employed the Group independent
component analysis (ICA) approach to isolate the DMN for the two groups by analyzing the resting-state fMRI data from
a group of 12 patients with dPD and a group of 12 age-matched ndPD subjects. Between-group comparison of the
functional connectivity in the DMN was then performed to examine the impact of depression on the intrinsic activity in
PD. We found 1) the core region from the network the medial prefrontal cortex (MPFC) show significant decreased
activity in dPD group compared with ndPD group; 2) the activity in MPFC has significant negative correlation with
behavioral measure; 3) the resting activity intensity of MPFC is suggested to be a promising biomarker for distinguishing
dPD from ndPD.
Task-based neuroimaging studies revealed that different attention operations were carried out by the functional
interaction and cooperation between two attention systems: the dorsal attention network (DAN) and the ventral attention
network (VAN), which were respectively involved in the "top-down" endogenous attention orienting and the "bottomup"
exogenous attention reorienting process. Recent focused resting functional MRI (fMRI) studies found the two
attention systems were inherently organized in the human brain regardless of whether or not the attention process were
required, but how the two attention systems interact with each other in the absence of task is yet to be investigated. In
this study, we first separated the DAN and VAN by applying the group independent component analysis (ICA) to the
resting fMRI data acquired from 12 healthy young subjects, then used Gaussian Bayesian network (BN) learning
approach to explore the plausible effective connectivity pattern of the two attention systems. It was found regions from
the same attention network were strongly intra-dependent, and all the connections were located in the information flow
from VAN to DAN, which suggested that an orderly functional interactions and information exchanges between the two
attention networks existed in the intrinsic spontaneous brain activity, and the inherent connections might benefit the
efficient cognitive process between DAN and VAN, such as the "top-down" and "bottom-up" reciprocal interaction when
attention-related tasks were involved.
Motor imagery training, as an effective strategy, has been more and more applied to mental disorders rehabilitation and
motor skill learning. Studies on the neural mechanism underlying motor imagery have suggested that such effectiveness
may be related to the functional congruence between motor execution and motor imagery. However, as compared to the
studies on motor imagery, the studies on motor imagery training are much fewer. The functional alterations associated
with motor imagery training and the effectiveness of motor imagery training on motor performance improvement still
needs further investigation. Using fMRI, we employed a sequential finger tapping paradigm to explore the functional
alterations associated with motor imagery training in both motor execution and motor imagery task. We hypothesized
through 14 consecutive days motor imagery training, the motor performance could be improved and the functional
congruence between motor execution and motor imagery would be sustained form pre-training phase to post-training
phase. Our results confirmed the effectiveness of motor imagery training in improving motor performance and
demonstrated in both pre and post-training phases, motor imagery and motor execution consistently sustained the
congruence in functional neuroanatomy, including SMA (supplementary motor cortex), PMA (premotor area); M1(
primary motor cortex) and cerebellum. Moreover, for both execution and imagery tasks, a similar functional alteration
was observed in fusiform through motor imagery training. These findings provided an insight into the effectiveness of
motor imagery training and suggested its potential therapeutic value in motor rehabilitation.
KEYWORDS: Independent component analysis, Brain, Functional magnetic resonance imaging, Head, Data analysis, Data acquisition, Shape memory alloys, Data processing, Neuroimaging, Signal processing
Real-time functional magnetic resonance imaging (rtfMRI) is a new technique which can present (feedback) brain
activity during scanning. Through fast acquisition and online analysis of BOLD signal, fMRI data are processed within
one TR. Current rtfMRI provides an activation map under specific task mainly through the GLM analysis to select region
of interest (ROI). This study was based on independent component analysis (ICA) and used the result of fast ICA
analysis to select the node of the functional network as the ROI. Real-time brain activity within the ROI was presented to
the subject who needed to find strategies to control his brain activity. The whole real-time processes involved three parts:
pre-processing (including head motion correction and smoothing), fast ICA analysis and feedback. In addition, the result
of fast head motion correction was also presented to the experimenter in a curve diagram. Based on the above analysis
processes, a real time feedback experiment with a motor imagery task was performed. An overt finger movement task as
localizer session was adopted for ICA analysis to get the motor network. Supplementary motor area (SMA) in such
network was selected as the ROI. During the feedback session, the average of BOLD signals within ROI was presented
to the subjects for self-regulation under a motor imagery task. In this experiment, TR was 1.5 seconds, and the whole
time of processing and presentation was within 1 second. Experimental results not only showed that the SMA was
controllable, but also proved that the analysis method was effective.
Spatial Independent component analysis (sICA) has been successfully used to analyze functional magnetic resonance
(fMRI) data. However, the application of ICA was limited in multi-task fMRI data due to the potential spatial
dependence between task-related components. Long et al. (2009) proposed ICA with linear projection (ICAp) method
and demonstrated its capacity to solve the interaction among task-related components in multi-task fMRI data of single
subject. However, it's unclear that how to perform ICAp over a group of subjects. In this study, we proposed a group
analysis framework on multi-task fMRI data by combining ICAp with the temporal concatenation method reported by
Calhoun (2001). The results of real fMRI experiment containing multiple visual processing tasks demonstrated the
feasibility and effectiveness of the group ICAp method. Moreover, compared to the GLM method, the group ICAp
method is more sensitive to detect the regions specific to each task.
KEYWORDS: Functional magnetic resonance imaging, Independent component analysis, Data modeling, Brain, Signal to noise ratio, Interference (communication), Data analysis, Computer simulations, Superposition, Data processing
General linear model (GLM) and independent component analysis (ICA) are widely used methods in the community of
functional magnetic resonance imaging (fMRI) data analysis. GLM and ICA are all assuming that fMRI components are
location locked. Here we extend the Differentially variable component analysis (dVCA) and introduce it into fMRI data
to analyze the transient changes during fMRI experiments which are ignored in GLM and ICA. We apply the extended
dVCA to model fMRI images as the linear combination of ongoing activity and multiple fMRI components. We test our
extended dVCA method on simulated images that mimicked the fMRI slice images containing two components, and
employ the iterative maximum a posteriori (MAP) solution succeed to estimate each component's time-invariant spatial
patterns, and its time-variant amplitude scaling factors and location shifts. The extended dVCA algorithm also identify
two fMRI components that reflect the fact of hemispheric asymmetry for motor area in another test with fMRI data
acquired with the block design task of right/left hand finger tapping alternately. This work demonstrates that our
extended dVCA method is robustness to detect the variability of the fMRI components that maybe existent during the
fMRI experiments.
Gray matter volume and cortical thickness are two important indices widely used to detect neuropathological changes in
brain structural magnetic resonance imaging. Using optimized voxel-based morphometry (VBM) protocol and
surface-based cortical thickness measure, this study comprehensively investigated the regional changes in cortical gray
matter volume and cortical thickness in Alzheimer's disease (AD). Thirteen patients with AD and fourteen age- and
gender-matched healthy controls were included in this study. Results showed that voxel-based gray matter volume and
cortical thickness reductions were highly correlated in the temporal lobe and its medial structure in AD. Moreover
significant reduced cortical regions of gray matter volume were obviously more than that of cortical thickness. These
findings suggest that gray matter volume and cortical thickness, as two important imaging markers, are effective indices
for detecting the neuroanatomical alterations and help us understand the neuropathology from different views in AD.
KEYWORDS: Functional magnetic resonance imaging, Independent component analysis, Data modeling, Brain, Data analysis, Neural networks, Magnetic resonance imaging, Data processing, Convolution, Feature extraction
The existence of the potential non-independency between task-related components in multi-task functional magnetic
resonance imaging (fMRI) studies limits the general application of Independent Component Analysis (ICA) method. The
ICA with projection (ICAp) method proposed by Long (2009, HBM) demonstrated its capacity to solve the interaction
among task-related components of multi-task fMRI data. The basic idea of projection is to remove the influence of the
uninteresting tasks through projection in order to extract one interesting task-related component. However, both the
stimulus paradigm of each task and the homodynamic response function (HRF) are essential for the projection. Due to
the noises in the data and the variability of the HRF across the voxels and subjects, the ideal time course of each task for
projection would be deviant from the true value, which might worsen the ICAp results. In order to make the time courses
for projection closer to the true value, the iterative ICAp is proposed in this study. The iterative ICAp is based on the
assumption that the task-related time courses extracted from the fMRI data by ICAp is more approximate to the true
value than the ideal reference function. Simulated experiment proved that both the spatial detection power and the
temporal accuracy of time course were increased for each task-related component. Moreover, the results of the real
two-task fMRI data were also improved by the iterative ICAp method.
KEYWORDS: Brain, Functional magnetic resonance imaging, Independent component analysis, Magnetic resonance imaging, Brain mapping, Neuroimaging, Scanners, Data processing, Data acquisition, Principal component analysis
Resting-state functional MRI (fMRI) studies have suggested the posterior cingulate cortex (PCC) plays a pivotal role in
the default mode network (DMN), a set of co-activated brain regions characterizing the resting-state brain. Concerning
this finding we propose the following questions in this study: Does PCC consistently play the equally crucial role in the
DMN across different subjects, such as healthy young and healthy old subjects? Whether the fMRI scan environments or
parameters would affect the results? To address these questions, we collected resting-state fMRI data on four groups of
subjects: two healthy young groups scanned under 3-T and 1.5-T MRI systems respectively, and two healthy elderly
groups both scanned under 3-T MRI system but with different scan parameters. Then group independent component
analysis was used to isolate the DMN, and partial correlation analysis was employed to reveal the direct interactions
between brain regions from the DMN. Finally, we measured the connectivity between brain regions based on the number
of significantly interacted links to every region within this network. We found that PCC was the brain region consistently
having the largest number of directly interacted regions in the four groups, suggesting the pivotal role of PCC in the
DMN was stable and consistent across healthy subjects. The results also suggested the function of PCC would be more
critical in healthy elderly subjects compared with healthy young subjects. And the factors of scan environments and
parameters did not show any obvious impact on the above conclusions in this investigation.
KEYWORDS: Brain, Independent component analysis, Functional magnetic resonance imaging, Statistical analysis, Neuroimaging, Testing and analysis, Data modeling, Principal component analysis, Data acquisition, Analytical research
This work proposed to use the linear Gaussian Bayesian network (BN) to construct the effective connectivity model of
the brain's default mode network (DMN), a set of regions characterized by more increased neural activity during
rest-state than most goal-oriented tasks. In a complete unsupervised data-driven manner, Bayesian information criterion
(BIC) based learning approach was utilized to identify a highest scored network whose nodes (brain regions) were
selected based on the result from the group independent component analysis (Group ICA) examining the DMN. We put
forward to adopt the statistical significance testing method for regression coefficients used in stepwise regression
analysis to further refine the network identified by BIC. The final established BN, learned from the functional magnetic
resonance imaging (fMRI) data acquired from 12 healthy young subjects during rest-state, revealed that the hippocampus
(HC) was the most influential brain region that affected activities in all other regions included in the BN. In contrast, the
posterior cingulate cortex (PCC) was influenced by other regions, but had no reciprocal effects on any other region.
Overall, the configuration of our BN illustrated that a prominent connection from HC to PCC existed in the DMN.
Recently, evidences from fMRI studies have shown that there was decreased activity among the default-mode network in
Alzheimer's disease (AD), and DTI researches also demonstrated that demyelinations exist in white matter of AD
patients. Therefore, combining these two MRI methods may help to reveal the relationship between white matter
damages and alterations of the resting state functional connectivity network. In the present study, we tried to address this
issue by means of correlation analysis between DTI and resting state fMRI images. The default-mode networks of AD
and normal control groups were compared to find the areas with significantly declined activity firstly. Then, the white
matter regions whose fractional anisotropy (FA) value correlated with this decline were located through multiple
regressions between the FA values and the BOLD response of the default networks. Among these correlating white
matter regions, those whose FA values also declined were found by a group comparison between AD patients and
healthy elderly control subjects. Our results showed that the areas with decreased activity among default-mode network
included left posterior cingulated cortex (PCC), left medial temporal gyrus et al. And the damaged white matter areas
correlated with the default-mode network alterations were located around left sub-gyral temporal lobe. These changes
may relate to the decreased connectivity between PCC and medial temporal lobe (MTL), and thus correlate with the
deficiency of default-mode network activity.
Functional network connectivity (FNC) measures the temporal dependency among the time courses of functional
networks. However, the marginal correlation between two networks used in the classic FNC analysis approach doesn't
separate the FNC from the direct/indirect effects of other networks. In this study, we proposed an alternative approach
based on partial correlation to evaluate the FNC, since partial correlation based FNC can reveal the direct interaction
between a pair of networks, removing dependencies or influences from others. Previous studies have demonstrated less
task-specific activation and less rest-state activity in Alzheimer's disease (AD). We applied present approach to contrast
FNC differences of resting state network (RSN) between AD and normal controls (NC). The fMRI data under resting
condition were collected from 15 AD and 16 NC. FNC was calculated for each pair of six RSNs identified using Group
ICA, thus resulting in 15 (2 out of 6) pairs for each subject. Partial correlation based FNC analysis indicated 6 pairs
significant differences between groups, while marginal correlation only revealed 2 pairs (involved in the partial
correlation results). Additionally, patients showed lower correlation than controls among most of the FNC differences.
Our results provide new evidences for the disconnection hypothesis in AD.
Using optimized voxel-based morphometry (VBM), this study systematically investigated the differences and similarities
of brain structural changes during the early three developmental periods of human lives: childhood, adolescence and
young adulthood. These brain changes were discussed in relationship to the corresponding cognitive function
development during these three periods. Magnetic Resonance Imaging (MRI) data from 158 Chinese healthy children,
adolescents and young adults, aged 7.26 to 22.80 years old, were included in this study. Using the customized brain
template together with the gray matter/white matter/cerebrospinal fluid prior probability maps, we found that there were
more age-related positive changes in the frontal lobe, less in hippocampus and amygdala during childhood, but more in
bilateral hippocampus and amygdala and left fusiform gyrus during adolescence and young adulthood. There were more
age-related negative changes near to central sulcus during childhood, but these changes extended to the frontal and
parietal lobes, mainly in the parietal lobe, during adolescence and young adulthood, and more in the prefrontal lobe
during young adulthood. So gray matter volume in the parietal lobe significantly decreased from childhood and
continued to decrease till young adulthood. These findings may aid in understanding the age-related differences in
cognitive function.
Using optimized voxel-based morphometry (VBM), this study systematically investigated gender differences in brain
development through magnetic resonance imaging (MRI) data in 158 Chinese normal children and adolescents aged 7.26
to 22.80 years (mean age 15.03±4.70 years, 78 boys and 80 girls). Gender groups were matched for measures of age,
handedness, education level. The customized brain templates, including T1-weighted image and gray matter (GM)/white
matter (WM)/cerebro-spinal fluid (CSF) prior probability maps, were created from all participants. Results showed that
the total intracranial volume (TIV), global absolute GM and global WM volume in girls were significantly smaller than
those in boys. The hippocampus grew faster in girls than that in boys, but the amygdala grew faster in boys than that in
girls. The rate of regional GM decreases with age was steeper in the left superior parietal lobule, bilateral inferior parietal
lobule, left precuneus, and bilateral supramarginal gyrus in boys compared to girls, which was possibly related to better
spatial processing ability in boys. Regional GM volumes were greater in bilateral superior temporal gyrus, bilateral
inferior frontal gyrus and bilateral middle frontal gyrus in girls. Regional WM volumes were greater in the left temporal
lobe, right inferior parietal and bilateral middle frontal gyrus in girls. The gender differences in the temporal and frontal
lobe maybe be related to better language ability in girls. These findings may aid in understanding the differences in
cognitive function between boys and girls.
In vivo white matter tractography by diffusion tensor imaging (DTI) accurately represents the organizational architecture
of white matter in the vicinity of brain lesions and especially ischemic brain. In this study, we suggested an improved
fiber tracking algorithm based on TEND, called TENDAS, for tensor deflection with adaptive stepping, which had been
introduced a stepping framework for interpreting the algorithm behavior as a function of the tensor shape (linear-shaped
or not) and tract history. The propagation direction at each step was given by the deflection vector. TENDAS
tractography was used to examine a 17-year-old recovery patient with congenital right hemisphere artery stenosis
combining with fMRI. Meaningless picture location was used as spatial working memory task in this study. We detected
the shifted functional localization to the contralateral homotypic cortex and more prominent and extensive left-sided
parietal and medial frontal cortical activations which were used directly as seed mask for tractography for the
reconstruction of individual spatial parietal pathways. Comparing with the TEND algorithms, TENDAS shows smoother
and less sharp bending characterization of white matter architecture of the parietal cortex. The results of this preliminary
study were twofold. First, TENDAS may provide more adaptability and accuracy in reconstructing certain anatomical
features, whereas it is very difficult to verify tractography maps of white matter connectivity in the living human brain.
Second, our study indicates that combination of TENDAS and fMRI provide a unique image of functional cortical
reorganization and structural modifications of postischemic spatial working memory.
Magnetic resonance image (MRI) has provided an imageological support into the clinical diagnosis and prediction of
Alzheimer disease (AD) progress. Currently, the clinical use of MRI data on AD diagnosis is qualitative via visual
inspection and less accurate. To provide assistance to physicians in improving the accuracy and sensitivity of the AD
diagnose and the clinical outcome of the disease, we developed a computer-assisted analysis package that analyzed the
MRI data of an individual patient in comparison with a group of normal controls. The package is based on the principle
of the well established and widely used voxel-based morphometry (VBM) and SPM software. All analysis procedure is
automated and streamlined. With only one mouse-click, the whole procedure was finished within 15 minutes. With the
interactive display and anatomical automatic labeling toolbox, the final result and report supply the brain regional
structure difference, the quantitative assessment and visual inspections by physicians and scientific researcher. The brain
regions which affected by AD are consonant in the main with the clinical diagnosis, which are reviewed by physicians.
In result, the computer package provides physician with an automatic and assistant tool for prediction using MRI. This
package could be valuable tool assisting physicians in making their clinical diagnosis decisions.
Little is known about the difference of functional connectivity of semantic task between the recovery aphasic patients
and normal subject. In this paper, an fMRI experiment was performed in a patient with aphasia following a left-sided
ischemic lesion and normal subject. Picture naming was used as semantic activation task in this study. We compared the
preliminary functional connectivity results of the recovery aphasic patient with the normal subject. The fMRI data were
separated by independent component analysis (ICA) into 90 components. According to our experience and other papers,
we chose a region of interest (ROI) of semantic (x=-57, y=15, z=8, r=11mm). From the 90 components, we chose one
component as the functional connectivity of the semantic ROI according to one criterion. The criterion is the mean value
of the voxels in the ROI. So the component of the highest mean value of the ROI is the functional connectivity of the
ROI. The voxel with its value higher than 2.4 was thought as activated (p<0.05). And the functional connectivity
networks of the normal subjects were t-tested as group network. From the result, we can know the semantic functional
connectivity of stroke aphasic patient and normal subjects are different. The activated areas of the left inferior frontal
gyrus and inferior/middle temporal gyrus are larger than the ones of normal. The activated area of the right inferior
frontal gyrus is smaller than the ones of normal. The functional connectivity of stroke aphasic patient under semantic
condition is different with the normal one. The focus of the stroke aphasic patient can affect the functional connectivity.
In contrast to the FMRI methods widely used up to now, this method try to understand more profoundly how the brain
systems work under sentence processing task map accurately the spatiotemporal patterns of activity of the large
neuronal populations in the human brain from the analysis of ERP data recorded on the brain scalp. In this study, an
event-related brain potential (ERP) paradigm to record the on-line responses to the processing of sentences is chosen as
an example. In order to give attention to both utilizing the ERPs' temporal resolution of milliseconds and overcoming
the insensibility of cerebral location ERP sources, we separate these sources in space and time based on a combined
method of independent component analysis (ICA) and low-resolution tomography (LORETA) algorithms. ICA blindly
separate the input ERP data into a sum of temporally independent and spatially fixed components arising from distinct
or overlapping brain or extra-brain sources. And then the spatial maps associated with each ICA component are
analyzed, with use of LORETA to uniquely locate its cerebral sources throughout the full brain according to the
assumption that neighboring neurons are simultaneously and synchronously activated. Our results show that the cerebral
computation mechanism underlies content words reading is mediated by the orchestrated activity of several spatially
distributed brain sources located in the temporal, frontal, and parietal areas, and activate at distinct time intervals and are
grouped into different statistically independent components. Thus ICA-LORETA analysis provides an encouraging and
effective method to study brain dynamics from ERP.
Effective connectivity of brain regions based on brain data (e.g. EEG, fMRI, etc.) is a focused research at present. Many
researchers tried to investigate it using different methods. Granger causality model (GCM) is presently used to
investigate effective connectivity of brain regions more and more. It can explore causal relationship between time series,
meaning that if a time-series y causes x, then knowledge of y should help predict future values of x. In present work,
time invariant GCM was applied to fMRI data considering slow changing of blood oxygenation level dependent
(BOLD). The time invariant GCM often requires determining model order, estimating model parameters and significance
test. In particular, we extended significance test method to make results more reasonable. The fMRI data were acquired
from finger movement experiment of two right-handed subjects. We obtained the activation maps of two subjects using
SPM'2 software firstly. Then we chose left SMA and left SMC as regions of interest (ROIs) with different radiuses, and
calculated causality from left SMA to left SMC using the mean time courses of the two ROIs. The results from both
subjects showed that left SMA influenced on left SMC. Hence GCM was suggested to be an effective approach in
investigation of effective connectivity based on fMRI data.
Voxel-based morphometry (VBM) is an automated and objective image analysis technique for detecting differences in
regional concentration or volume of brain tissue composition based on structural magnetic resonance (MR) images.
VBM has been used widely to evaluate brain morphometric differences between different populations, but there isn't an
evaluation system for its validation until now. In this study, a quantitative and objective evaluation system was
established in order to assess VBM performance. We recruited twenty normal volunteers (10 males and 10 females, age
range 20-26 years, mean age 22.6 years). Firstly, several focal lesions (hippocampus, frontal lobe, anterior cingulate,
back of hippocampus, back of anterior cingulate) were simulated in selected brain regions using real MRI data. Secondly,
optimized VBM was performed to detect structural differences between groups. Thirdly, one-way ANOVA and post-hoc
test were used to assess the accuracy and sensitivity of VBM analysis. The results revealed that VBM was a good
detective tool in majority of brain regions, even in controversial brain region such as hippocampus in VBM study.
Generally speaking, much more severity of focal lesion was, better VBM performance was. However size of focal lesion
had little effects on VBM analysis.
Vegetables are widely planted all over China, but they often suffer from the some diseases. A method of major technical
and economical importance is introduced in this paper, which explores the feasibility of implementing fast and reliable
automatic identification of vegetable diseases and their infection grades from color and morphological features of leaves.
Firstly, leaves are plucked from clustered plant and pictures of the leaves are taken with a CCD digital color camera.
Secondly, color and morphological characteristics are obtained by standard image processing techniques, for examples,
Otsu thresholding method segments the region of interest, image opening following closing algorithm removes noise,
Principal Components Analysis reduces the dimension of the original features. Then, a recently proposed boosting
algorithm AdaBoost. M2 is applied to RBF networks for diseases classification based on the above features, where the
kernel function of RBF networks is Gaussian form with argument taking Euclidean distance of the input vector from a
center. Our experiment performs on the database collected by Chinese Academy of Agricultural Sciences, and result
shows that Boosting RBF Networks classifies the 230 cucumber leaves into 2 different diseases (downy-mildew and
angular-leaf-spot), and identifies the infection grades of each disease according to the infection degrees.
KEYWORDS: Independent component analysis, Functional magnetic resonance imaging, Principal component analysis, Brain, Signal detection, Data acquisition, Solids, Shape memory alloys, Data centers, Neuroimaging
Independent component analysis (ICA) method can be used to separate fMRI data into some task-related independent components, including one consistently task-related (CTR) and several transiently task-related (TTR) components. However, the weights, with which the CTR and TTRs contribute to the final task component, are often unknown, but are important for finding its relevant spatial activation area. Here we propose a new ICA post-processing method alternative to combine not only these CTR and TTRs which sometimes are judged in a subjective manner, but also others in an effort to identify a comprehended and summed spatial pattern that is responsible for the behavior under investigation. This proposed procedure has been successfully used in principal component analysis (PCA) based scaled subprofile modeling (SSM). Adopting this newly proposed approach, we essentially refer the ICA exploratory findings to a hypothesized temporal brain response pattern (reference function). Basically, we will use linear regression method to seek the relationship between the reference function and time courses of multi components generated from the ICA procedure. The linear regression coefficients are then used as relative weights in generating the final summed spatial pattern. Moreover, this approach allows a researcher to use T-test to statistically infer the importance of each independent component in its contribution to the final pattern and consequently the contribution to the cognitive process. Experiment result also shows that the spatial activation of the final task component becomes more accurate.
Kewei Chen, Xiaolin Ge, Li Yao, Dan Bandy, Gene Alexander, Anita Prouty, Christine Burns, Xiaojie Zhao, Xiaotong Wen, Ronald Korn, Michael Lawson, Eric Reiman
Having approved fluorodeoxyglucose positron emission tomography (FDG PET) for the diagnosis of Alzheimer's disease (AD) in some patients, the Centers for Medicare and Medicaid Services suggested the need to develop and test analysis techniques to optimize diagnostic accuracy. We developed an automated computer package comparing an individual's FDG PET image to those of a group of normal volunteers. The normal control group includes FDG-PET images from 82 cognitively normal subjects, 61.89±5.67 years of age, who were characterized demographically, clinically, neuropsychologically, and by their apolipoprotein E genotype (known to be associated with a differential risk for AD). In addition, AD-affected brain regions functionally defined as based on a previous study (Alexander, et al, Am J Psychiatr, 2002) were also incorporated. Our computer package permits the user to optionally select control subjects, matching the individual patient for gender, age, and educational level. It is fully streamlined to require minimal user intervention. With one mouse click, the program runs automatically, normalizing the individual patient image, setting up a design matrix for comparing the single subject to a group of normal controls, performing the statistics, calculating the glucose reduction overlap index of the patient with the AD-affected brain regions, and displaying the findings in reference to the AD regions. In conclusion, the package automatically contrasts a single patient to a normal subject database using sound statistical procedures. With further validation, this computer package could be a valuable tool to assist physicians in decision making and communicating findings with patients and patient families.
This study examined regional gray matter abnormalities across the whole brain in 19 patients with schizophrenia (12 males and 7 females), comparing with 11 normal volunteers (7 males and 4 females). The customized brain templates
were created in order to improve spatial normalization and segmentation. Then automated preprocessing of magnetic
resonance imaging (MRI) data was conducted using optimized voxel-based morphometry (VBM). The statistical voxel based analysis was implemented in terms of two-sample t-test model. Compared with normal controls, regional gray matter concentration in patients with schizophrenia was significantly reduced in the bilateral superior temporal gyrus, bilateral middle frontal and inferior frontal gyrus, right insula, precentral and parahippocampal areas, left thalamus and hypothalamus as well as, however, significant increases in gray matter concentration were not observed across the whole brain in the patients. This study confirms and extends some earlier findings on gray matter abnormalities in schizophrenic patients. Previous behavior and fMRI researches on schizophrenia have suggested that cognitive capacity
decreased and self-conscious weakened in schizophrenic patients. These regional gray matter abnormalities determined through structural MRI with optimized VBM may be potential anatomic underpinnings of schizophrenia.
In the article, a new idea has been brought out to study a traditional optical question, that is, fiber sensor was taken
accounted as an information system, which has been analyzed with the information theory. The author began the
analyses with the structure of the fiber sensor's core, i.e. microbend modulator, and then evaluated its performance
with the amount and strengthens of the impossible acquired information. The infection of the modulator's
characteristics has been discussed from the view of information theory, which has been proven by theoretically
deducing and experimental data. As the result, the author advanced the opinion that method based on optics
information theory can guide the process of the performance optimizing and the parameters designing.
Spatial normalization is a very important step in the processing of magnetic resonance imaging (MRI) data. So the quality of brain templates is crucial for the accuracy of MRI analysis. In this paper, using the classical protocol and the optimized protocol plus nonlinear deformation, we constructed the T1 whole brain templates and apriori brain tissue data from 69 Chinese pediatric MRI data (age 7-16 years). Then we proposed a new assessment method to evaluate our templates. 10 pediatric subjects were chosen to do the assessment as the following steps. First, the cerebellum region, the region of interest (ROI), was located on both the pediatric volume and the template volume by an experienced neuroanatomist. Second, the pediatric whole brain was mapped to the template with affine and nonlinear deformation. Third, the parameter, derived from the second step, was used to only normalize the ROI of the child to the ROI of the template. Last, the overlapping ratio, which described the overlapping rate between the ROI of the template and the normalized ROI of the child, was calculated. The mean of overlapping ratio normalized to the classical template was 0.9687, and the mean normalized to the optimized template was 0.9713. The results show that the two Chinese pediatric brain templates are comparable and their accuracy is adequate to our studies.
KEYWORDS: Independent component analysis, Functional magnetic resonance imaging, Data modeling, Neural networks, Solids, Data acquisition, Signal to noise ratio, Electroencephalography, Psychology, Evolutionary algorithms
Independent component analysis (ICA) is a technique that attempts to separate data into maximally independent groups. Several ICA algorithms have been proposed in the neural network literature. Among these algorithms applied to fMRI data, the Infomax algorithm has been used more widely so far. The Infomax algorithm maximizes the information transferred in a network of nonlinear units. The nonlinear transfer function is able to pick up higher-order moments of the input distributions and reduce the redundancy between units in the output and input. But the transfer function in the Infomax algorithm is a fixed Logistic function. In this paper, an improved Infomax algorithm is proposed. In order to make transfer function match the input data better, the we add a changeable parameter to the Logistic function and estimate the parameter from the input fMRI data in two methods, 1. maximizing the correlation coefficient between the transfer function and the cumulative distribution function (c.d.f), 2. minimizing the entropy distance based on the KL divergence between the transfer function and the c.d.f. We apply the improved Infomax algorithm to the processing of fMRI data, and the results show that the improved algorithm is more effective in terms of fMRI data separation.
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