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Dynamic Changes in the Mental Rotation Network Revealed by Pattern Recognition Analysis of fMRI Data

MOURAO-MIRANDA, Janaina; ECKER, Christine; SATO, Joao R.; BRAMMER, Michael
Fonte: M I T PRESS Publicador: M I T PRESS
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.65%
We investigated the temporal dynamics and changes in connectivity in the mental rotation network through the application of spatio-temporal support vector machines (SVMs). The spatio-temporal SVM [Mourao-Miranda, J., Friston, K. J., et al. (2007). Dynamic discrimination analysis: A spatial-temporal SVM. Neuroimage, 36, 88-99] is a pattern recognition approach that is suitable for investigating dynamic changes in the brain network during a complex mental task. It does not require a model describing each component of the task and the precise shape of the BOLD impulse response. By defining a time window including a cognitive event, one can use spatio-temporal fMRI observations from two cognitive states to train the SVM. During the training, the SVM finds the discriminating pattern between the two states and produces a discriminating weight vector encompassing both voxels and time (i.e., spatio-temporal maps). We showed that by applying spatio-temporal SVM to an event-related mental rotation experiment, it is possible to discriminate between different degrees of angular disparity (0 degrees vs. 20 degrees, 0 degrees vs. 60 degrees, and 0 degrees vs. 100 degrees), and the discrimination accuracy is correlated with the difference in angular disparity between the conditions. For the comparison with highest accuracy (08 vs. 1008)...

Dynamic functional connectivity of BOLD fMRI signal during both rest and task execution states

Brito, Joana Paula Fontinha de
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2014 Português
Relevância na Pesquisa
36.65%
Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2014; A conectividade cerebral é um tema muito atual na área das neurociências. A dinâmica a conectividade tem sido um tema muito explorado ultimamente com o objetivo de se descobrir mais sobre os processos cerebrais relacionados com sinais neuronais em bandas restritas de frequência e ainda compreender as diferenças entre repouso e execução de tarefas. O objetivo principal do presente trabalho consistiu no desenvolvimento de um procedimento para o estudo da conectividade dinâmica baseado na análise da coerência através da Transformada "Wavelet" que proporciona especificidade no tempo e na frequência. A abordagem implementada baseou-se em duas hipóteses diferentes de comunicação neuronal. A primeira considera que dois sinais neuronais oscilatórios comunicam durante períodos de coerência de magnitude elevada e a segunda considera que a comunicação neuronal ocorre em períodos de acoplamento de fase. O uso das duas hipóteses permitiu obter, respectivamente, dois perfis de comunicação neuronal. Uma vez que, as distribuições nulas dos perfis de coerência de magnitude e de acoplamento de fase são desconhecidas...

Galvanic vestibular stimulator for fMRI studies

Della-Justina,Hellen Mathei; Manczak,Tiago; Winkler,Anderson Marcelo; Araújo,Dráulio Barros de; Souza,Mauren Abreu de; Amaro Junior,Edson; Gamba,Humberto Remigio
Fonte: SBEB - Sociedade Brasileira de Engenharia Biomédica Publicador: SBEB - Sociedade Brasileira de Engenharia Biomédica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 Português
Relevância na Pesquisa
36.65%
INTRODUCTION: Areas of the brain that are associated with the vestibular system can be activated using galvanic vestibular stimulation. These areas can be studied through a combination of galvanic vestibular stimulation with functional magnetic resonance imaging (fMRI). In order to provide an appropriate sequence of galvanic stimulation synchronous with the MRI pulse sequence, a specific electronic device that was built and assessed is presented. METHODS: The electronic project of the GVS is divided in analog and digital circuits. The analog circuits are mounted in an aluminum case, supplied by sealed batteries, and goes inside the MRI room near to the feet of the subject. The digital circuits are placed in the MRI control room. Those circuits communicate through each other by an optical fiber. Tests to verify the GVS-MRI compatibility were conducted. Silicone (in-house) and Ag/AgCl (commercial) electrodes were evaluated for maximum balance and minimal pain sensations. fMRI experiments were conducted in eight human volunteers. RESULTS: GVS-MRI compatibility experiments demonstrate that the GVS did not interfere with the MRI scanner functionality and vice versa. The circular silicone electrode was considered the most suitable to apply the galvanic vestibular stimulation. The 1 Hz stimulation sinusoid frequency produced the biggest balance and the less pain sensations when compared to 2 Hz. The GVS was capable of eliciting activation in the precentral and postcentral gyri...

Inhibitory control and the adolescent brain: a review of fMRI research

Jaeger,Antonio
Fonte: Pontificia Universidade Católica do Rio de Janeiro; Universidade de Brasília; Universidade de São Paulo Publicador: Pontificia Universidade Católica do Rio de Janeiro; Universidade de Brasília; Universidade de São Paulo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2013 Português
Relevância na Pesquisa
36.65%
Adolescence is a developmental period frequently characterized by impulsive behavior and suboptimal decision making, aspects that often result in increased rates of substance abuse, unprotected sex, and several other harmful behaviors. Functional magnetic resonance imaging (fMRI) studies have attempted to reveal the brain mechanisms that underlie the typical inhibitory control limitations associated with this developmental period. In the present review, all available studies in the PsycINFO, PubMed, and Web of Science databases that investigated this issue utilizing fMRI were analyzed. In contrast to adults, adolescents exhibited decreased activity in several brain regions associated with inhibitory control such as the dorsolateral prefrontal cortex, anterior cingulate cortex, and fronto-striatal regions. The decreased activity found in these regions may underlie the diminished inhibitory control abilities associated with this development period.

fMRI paradigm designing and post-processing tools

James, Jija S; Rajesh, PG; Chandran, Anuvitha VS; Kesavadas, Chandrasekharan
Fonte: Medknow Publications & Media Pvt Ltd Publicador: Medknow Publications & Media Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
36.65%
In this article, we first review some aspects of functional magnetic resonance imaging (fMRI) paradigm designing for major cognitive functions by using stimulus delivery systems like Cogent, E-Prime, Presentation, etc., along with their technical aspects. We also review the stimulus presentation possibilities (block, event-related) for visual or auditory paradigms and their advantage in both clinical and research setting. The second part mainly focus on various fMRI data post-processing tools such as Statistical Parametric Mapping (SPM) and Brain Voyager, and discuss the particulars of various preprocessing steps involved (realignment, co-registration, normalization, smoothing) in these software and also the statistical analysis principles of General Linear Modeling for final interpretation of a functional activation result.

Clinical utility of BOLD fMRI in preoperative work-up of epilepsy

Ganesan, Karthik; Ursekar, Meher
Fonte: Medknow Publications & Media Pvt Ltd Publicador: Medknow Publications & Media Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
36.65%
Surgical techniques have emerged as a viable therapeutic option in patients with drug refractory epilepsy. Pre-surgical evaluation of epilepsy requires a comprehensive, multiparametric, and multimodal approach for precise localization of the epileptogenic focus. Various non-invasive techniques are available at the disposal of the treating physician to detect the epileptogenic focus, which include electroencephalography (EEG), video-EEG, magnetic resonance imaging (MRI), functional MRI including blood oxygen level dependent (BOLD) techniques, single photon emission tomography (SPECT), and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). Currently, non-invasive high-resolution MR imaging techniques play pivotal roles in the preoperative detection of the seizure focus, and represent the foundation for successful epilepsy surgery. BOLD functional magnetic resonance imaging (fMRI) maps allow for precise localization of the eloquent cortex in relation to the seizure focus. This review article focuses on the clinical utility of BOLD (fMRI) in the pre-surgical work-up of epilepsy patients.

fMRI for mapping language networks in neurosurgical cases

Gupta, Santosh S
Fonte: Medknow Publications & Media Pvt Ltd Publicador: Medknow Publications & Media Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
36.65%
Evaluating language has been a long-standing application in functional magnetic resonance imaging (fMRI) studies, both in research and clinical circumstances, and still provides challenges. Localization of eloquent areas is important in neurosurgical cases, so that there is least possible damage to these areas during surgery, maintaining their function postoperatively, therefore providing good quality of life to the patient. Preoperative fMRI study is a non-invasive tool to localize the eloquent areas, including language, with other traditional methods generally used being invasive and at times perilous. In this article, we describe methods and various paradigms to study the language areas, in clinical neurosurgical cases, along with illustrations of cases from our institute.

Sex Differences in the Neurobiology of Fear Conditioning and Extinction: A Preliminary fMRI Study of Shared Sex Differences with Stress-Arousal Circuitry

Lebron-Milad, Kelimer; Linnman, Clas; Rougemount-Bücking, Ansgar; Abbs, Brandon R.; Milad, Mohammed Ragib; Zeidan, Mohammed A.; Holt, Daphne J.; Goldstein, Jill M.
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.65%
Background: The amygdala, hippocampus, medial prefrontal cortex (mPFC) and brain-stem subregions are implicated in fear conditioning and extinction, and are brain regions known to be sexually dimorphic. We used functional magnetic resonance imaging (fMRI) to investigate sex differences in brain activity in these regions during fear conditioning and extinction. Methods: Subjects were 12 healthy men comparable to 12 healthy women who underwent a 2-day experiment in a 3T MR scanner. Fear conditioning and extinction learning occurred on day 1 and extinction recall occurred on day 2. The conditioned stimuli were visual cues and the unconditioned stimulus was a mild electric shock. Skin conductance responses (SCR) were recorded throughout the experiment as an index of the conditioned response. fMRI data (blood-oxygen-level-dependent [BOLD] signal changes) were analyzed using SPM8. Results: Findings showed no significant sex differences in SCR during any experimental phases. However, during fear conditioning, there were significantly greater BOLD-signal changes in the right amygdala, right rostral anterior cingulate (rACC) and dorsal anterior cingulate cortex (dACC) in women compared with men. In contrast, men showed significantly greater signal changes in bilateral rACC during extinction recall. Conclusions: These results indicate sex differences in brain activation within the fear circuitry of healthy subjects despite similar peripheral autonomic responses. Furthermore...

Studying the Spatial Distribution of Physiological Effects on BOLD Signals Using Ultrafast fMRI

Tong, Yunjie; Frederick, Blaise deB.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.73%
The blood-oxygen-level dependent (BOLD) signal in functional MRI (fMRI) reflects both neuronal activations and global physiological fluctuations. These physiological fluctuations can be attributed to physiological low frequency oscillations (pLFOs), respiration, and cardiac pulsation. With typical TR values, i.e., 2 s or longer, the high frequency physiological signals (i.e., from respiration and cardiac pulsation) are aliased into the low frequency band, making it hard to study the individual effect of these physiological processes on BOLD. Recently developed multiband EPI sequences, which offer full brain coverage with extremely short TR values (400 ms or less) allow these physiological signals to be spectrally separated. In this study, we applied multiband resting state scans on nine healthy participants with TR = 0.4 s. The spatial distribution of each physiological process on BOLD fMRI was explored using their spectral features and independent component analysis (ICA). We found that the spatial distributions of different physiological processes are distinct. First, cardiac pulsation affects mostly the base of the brain, where high density of arteries exists. Second, respiration affects prefrontal and occipital areas, suggesting the motion associated with breathing might contribute to the noise. Finally...

The compensatory dynamic of inter-hemispheric interactions in visuospatial attention revealed using rTMS and fMRI

Plow, Ela B.; Cattaneo, Zaira; Carlson, Thomas A.; Alvarez, George A.; Pascual-Leone, Alvaro; Battelli, Lorella
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.65%
A balance of mutual tonic inhibition between bi-hemispheric posterior parietal cortices is believed to play an important role in bilateral visual attention. However, experimental support for this notion has been mainly drawn from clinical models of unilateral damage. We have previously shown that low-frequency repetitive TMS (rTMS) over the intraparietal sulcus (IPS) generates a contralateral attentional deficit in bilateral visual tracking. Here, we used functional magnetic resonance imaging (fMRI) to study whether rTMS temporarily disrupts the inter-hemispheric balance between bilateral IPS in visual attention. Following application of 1 Hz rTMS over the left IPS, subjects performed a bilateral visual tracking task while their brain activity was recorded using fMRI. Behaviorally, tracking accuracy was reduced immediately following rTMS. Areas ventro-lateral to left IPS, including inferior parietal lobule (IPL), lateral IPS (LIPS), and middle occipital gyrus (MoG), showed decreased activity following rTMS, while dorsomedial areas, such as Superior Parietal Lobule (SPL), Superior occipital gyrus (SoG), and lingual gyrus, as well as middle temporal areas (MT+), showed higher activity. The brain activity of the homologues of these regions in the un-stimulated...

Variational Bayesian causal connectivity analysis for fMRI

Luessi, Martin; Babacan, S. Derin; Molina, Rafael; Booth, James R.; Katsaggelos, Aggelos K.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.65%
The ability to accurately estimate effective connectivity among brain regions from neuroimaging data could help answering many open questions in neuroscience. We propose a method which uses causality to obtain a measure of effective connectivity from fMRI data. The method uses a vector autoregressive model for the latent variables describing neuronal activity in combination with a linear observation model based on a convolution with a hemodynamic response function. Due to the employed modeling, it is possible to efficiently estimate all latent variables of the model using a variational Bayesian inference algorithm. The computational efficiency of the method enables us to apply it to large scale problems with high sampling rates and several hundred regions of interest. We use a comprehensive empirical evaluation with synthetic and real fMRI data to evaluate the performance of our method under various conditions.

Zur neuronalen Repräsentation bimanuellen Lernens im menschlichen Gehirn : Untersuchungen mit funktioneller Kernspintomographie; Functional anatomy of bimanual coordination learning : a study with fMRI

Hansmann, Jessica
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.65%
Über die topographische Dynamik während des Erlernens von bimanuellen Sequenzen ist bisher wenig bekannt. Im EEG-Vorläuferexperiment (Andres et al., 1999) war die Hypothese entstanden, dass der initiale interhemisphärische Kohärenzanstieg bei der Fusion einer bimanuellen Fingerbewegung von Schrittmachern außerhalb von S1/M1 mitgesteuert würde. Diese Studie hat das Ziel, ein mögliches verstreutes kortikales Netzwerk zu evaluieren, welches verantwortlich ist für das Erlernen und Spielen von komplexen bimanuellen Sequenzen, sowie Kandidatenregionen für eine mögliche Schrittmacher- bzw. Autopilotfunktion topographisch zu lokalisieren. Die neuronalen Korrelate dieser Prozesse wurden bei acht erwachsenen rechtshändigen gesunden Probanden mittels funktioneller Kernspintomographie (fMRT) untersucht. Die Aufgabe der Testpersonen bestand in einem Verzahnen von einer gelernten rechts- und einer gelernten linkshändigen Sequenz von jeweils acht Tastendrücken bei 1 Hz in eine bimanuelle 2 Hz Sequenz. FMRT-Messungen wurden während der initialen Lernphase und über weitere drei Lernstadien aufgenommen, unterbrochen durch kurze Perioden von spezifischem Training, um die fusionierten Sequenzen in Ausübung und Korrektheit zu verbessern. Die Zahl der korrekten Sequenzen und Tastendrücke verbesserte sich während der Lernstadien. Das frühe Lernstadium aktivierte ein Netzwerk mit den bilateralen primären sensomotorischen Kortices...

Generalized likelihood ratio detection for fMRI using complex data

Nan, F.Y.; Nowak, Robert David; Nan, F.Y.; Nowak, Robert David
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.73%
Journal Paper; The majority of fMRI studies obtain functional information using statistical tests based on the magnitude image reconstructions. Recently, a complex correlation (CC) test was proposed based on teh complex image data in order to take advantage of phase information in teh signal. However, the CC test ignores additional phase information in the baseline component of the data. In this paper, a new detector for fMRI based on a Generalized Likelihood Ration Test (GLRT) is proposed. The GLRT exploits the fact that the fMRI response signal as well as the baseline component of the data share a common phase. Theoretical analysis and Monte Carlo simulation are used to explore the performance of the new detector. At relatively low signal intensities, the GLRT outperforms both the standard magnitude data test and the CC test. At high signal intensities, the GLRT performs as well as teh standard magnitude data test and significantly better than the CC test.

Effect of scanner acoustic background noise on strict resting-state fMRI

Rondinoni,C.; Amaro Jr,E.; Cendes,F.; Santos,A.C.dos; Salmon,C.E.G.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2013 Português
Relevância na Pesquisa
36.73%
Functional MRI (fMRI) resting-state experiments are aimed at identifying brain networks that support basal brain function. Although most investigators consider a ‘resting-state’ fMRI experiment with no specific external stimulation, subjects are unavoidably under heavy acoustic noise produced by the equipment. In the present study, we evaluated the influence of auditory input on the resting-state networks (RSNs). Twenty-two healthy subjects were scanned using two similar echo-planar imaging sequences in the same 3T MRI scanner: a default pulse sequence and a reduced “silent” pulse sequence. Experimental sessions consisted of two consecutive 7-min runs with noise conditions (default or silent) counterbalanced across subjects. A self-organizing group independent component analysis was applied to fMRI data in order to recognize the RSNs. The insula, left middle frontal gyrus and right precentral and left inferior parietal lobules showed significant differences in the voxel-wise comparison between RSNs depending on noise condition. In the presence of low-level noise, these areas Granger-cause oscillations in RSNs with cognitive implications (dorsal attention and entorhinal), while during high noise acquisition, these connectivities are reduced or inverted. Applying low noise MR acquisitions in research may allow the detection of subtle differences of the RSNs...

A spatio-temporal nonparametric Bayesian variable selection model of fMRI data for clustering correlated time courses

Zhang, Linlin; Guindani, Michele; Versace, Francesco; Vannucci, Marina
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Journal article; Text; post-print
Português
Relevância na Pesquisa
36.73%
In this paper we present a novel wavelet-based Bayesian nonparametric regression model for the analysis of functional magnetic resonance imaging (fMRI) data. Our goal is to provide a joint analytical framework that allows to detect regions of the brain which exhibit neuronal activity in response to a stimulus and, simultaneously, infer the association, or clustering, of spatially remote voxels that exhibit fMRI time series with similar characteristics. We start by modeling the data with a hemodynamic response function (HRF) with a voxel-dependent shape parameter. We detect regions of the brain activated in response to a given stimulus by using mixture priors with a spike at zero on the coefficients of the regression model. We account for the complex spatial correlation structure of the brain by using a Markov random field (MRF) prior on the parameters guiding the selection of the activated voxels, therefore capturing correlation among nearby voxels. In order to infer association of the voxel time courses, we assume correlated errors, in particular long memory, and exploit the whitening properties of discrete wavelet transforms. Furthermore, we achieve clustering of the voxels by imposing a Dirichlet process (DP) prior on the parameters of the long memory process. For inference...

Methodological advances in spinal cord and brainstem fMRI provide an unprecedented view of human pain processing and alterations to pain mechanisms in fibromyalgia

Bosma, RACHAEL
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.73%
Functional MRI of the human spinal cord and brainstem has tremendous potential to enhance our basic understanding of healthy subcortical function, and impact our ability to accurately diagnose and treat injury and disease. Despite this potential, there are many challenges and limitations that must be overcome before this technique can be of clinical use. The objectives of this thesis are to develop spinal cord and brainstem functional imaging methods in order to sensitively characterize sensory and pain processing in healthy humans, and to assess changes in the function of these structures that arise from a prevalent chronic pain condition, fibromyalgia (FM). Therefore, we first conducted a rigorous assessment of acquisition parameters and analytical approaches in order to reduce the impact of physiological noise and optimize our sensitivity for detecting neural function in the spinal cord and brainstem. These methodological developments were then applied to characterize the fMRI response to sensory stimuli presented in block and stepwise paradigms designed to probe different aspects of the sensory response. Results of this study confirmed the sensitivity of our fMRI methods for detecting subtle changes in sensory processing and highlight the importance of careful paradigm selection. Building on these findings...

Mapping brain response to pain in fibromyalgia patients using temporal analysis of fMRI

Pujol Nuez, Jesús; López-Solà, Marina; Ortiz, Héctor; Vilanova, Joan Carles; Harrison, Ben J.; Yücel, Murat; Soriano Mas, Carles; Cardoner, Narcís; Deus Yela, Juan
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2009 Português
Relevância na Pesquisa
36.73%
Background: Nociceptive stimuli may evoke brain responses longer than the stimulus duration often partially detected by conventional neuroimaging. Fibromyalgia patients typically complain of severe pain from gentle stimuli. We aimed to characterize brain response to painful pressure in fibromyalgia patients by generating activation maps adjusted for the duration of brain responses. Methodology/Principal Findings: Twenty-seven women (mean age: 47.8 years) were assessed with fMRI. The sample included nine fibromyalgia patients and nine healthy subjects who received 4 kg/cm2 of pressure on the thumb. Nine additional control subjects received 6.8 kg/cm2 to match the patients for the severity of perceived pain. Independent Component Analysis characterized the temporal dynamics of the actual brain response to pressure. Statistical parametric maps were estimated using the obtained time courses. Brain response to pressure (18 seconds) consistently exceeded the stimulus application (9 seconds) in somatosensory regions in all groups. fMRI maps following such temporal dynamics showed a complete pain network response (sensory-motor cortices, operculo-insula, cingulate cortex, and basal ganglia) to 4 kg/cm2 of pressure in fibromyalgia patients. In healthy subjects...

fMRI activity in posterior parietal cortex relates to the perceptual use of binocular disparity for both signal-in-noise and feature difference tasks

Patten, Matthew L.; Welchman, Andrew E.
Fonte: PLoS Publicador: PLoS
Tipo: Article; published version
Português
Relevância na Pesquisa
36.73%
This is the final version of the article. It first appeared from PLOS via http://dx.doi.org/10.1371/journal.pone.0140696; Visually guided action and interaction depends on the brain?s ability to (a) extract and (b) discriminate meaningful targets from complex retinal inputs. Binocular disparity is known to facilitate this process, and it is an open question how activity in different parts of the visual cortex relates to these fundamental visual abilities. Here we examined fMRI responses related to performance on two different tasks (signal-in-noise ?coarse? and feature difference ?fine? tasks) that have been widely used in previous work, and are believed to differentially target the visual processes of signal extraction and feature discrimination. We used multi-voxel pattern analysis to decode depth positions (near vs. far) from the fMRI activity evoked while participants were engaged in these tasks. To look for similarities between perceptual judgments and brain activity, we constructed ?fMR-metric? functions that described decoding performance as a function of signal magnitude. Thereafter we compared fMR-metric and psychometric functions, and report an association between judged depth and fMRI responses in the posterior parietal cortex during performance on both tasks. This highlights common stages of processing during perceptual performance on these tasks.

7 Tesla fMRI Reveals Systematic Functional Organization for Binocular Disparity in Dorsal Visual Cortex

Goncalves, Nuno R.; Ban, Hiroshi; S?nchez-Panchuelo, Rosa M.; Francis, Susan T.; Schluppeck, Denis; Welchman, Andrew E.
Fonte: Society for Neuroscience Publicador: Society for Neuroscience
Tipo: Article; published version
Português
Relevância na Pesquisa
36.73%
This is the final version of the article. It was originally published in the Journal of Neuroscience, 18 February 2015, 35(7): 3056-3072; doi: 10.1523/JNEUROSCI.3047-14.2015.; The binocular disparity between the views of the world registered by the left and right eyes provides a powerful signal about the depth structure of the environment. Despite increasing knowledge of the cortical areas that process disparity from animal models, comparatively little is known about the local architecture of stereoscopic processing in the human brain. Here, we take advantage of the high spatial specificity and image contrast offered by 7 tesla fMRI to test for systematic organization of disparity representations in the human brain. Participants viewed random dot stereogram stimuli depicting different depth positions while we recorded fMRI responses from dorsomedial visual cortex. We repeated measurements across three separate imaging sessions. Using a series of computational modeling approaches, we report three main advances in understanding disparity organization in the human brain. First, we show that disparity preferences are clustered and that this organization persists across imaging sessions, particularly in area V3A. Second, we observe differences between the local distribution of voxel responses in early and dorsomedial visual areas...

Spatial Bayesian Variable Selection with Application to Functional Magnetic Resonance Imaging (fMRI)

Yang, Ying
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2011 Português
Relevância na Pesquisa
36.73%

Functional magnetic resonance imaging (fMRI) is a major neuroimaging methodology and have greatly facilitate basic cognitive neuroscience research. However, there are multiple statistical challenges in the analysis of fMRI data, including, dimension reduction, multiple testing and inter-dependence of the MRI responses. In this thesis, a spatial Bayesian variable selection (BVS) model is proposed for the analysis of multi-subject fMRI data. The BVS framework simultaneously account for uncertainty in model specific parameters as well as the model selection process, solving the multiple testing problem. A spatial prior incorporate the spatial relationship of the MRI response, accounting for their inter-dependence. Compared to the non-spatial BVS model, the spatial BVS model enhances the sensitivity and accuracy of identifying activated voxels.

; Thesis