Página 22 dos resultados de 8518 itens digitais encontrados em 0.007 segundos

PRN: a preprint service for catalyzing R-fMRI and neuroscience related studies

Yan, Chaogan; Li, Qingyang; Gao, Lei
Fonte: F1000Research Publicador: F1000Research
Tipo: Artigo de Revista Científica
Publicado em 22/12/2014 Português
Relevância na Pesquisa
26.73%
Sharing drafts of scientific manuscripts on preprint hosting services for early exposure and pre-publication feedback is a well-accepted practice in fields such as physics, astronomy, or mathematics. The field of neuroscience, however, has yet to adopt the preprint model. A reason for this reluctance might partly be the lack of central preprint services for the field of neuroscience. To address this issue, we announce the launch of Preprints of the R-fMRI Network (PRN), a community funded preprint hosting service. PRN provides free-submission and free hosting of manuscripts for resting state functional magnetic resonance imaging (R-fMRI) and neuroscience related studies. Submissions will be peer viewed and receive feedback from readers and a panel of invited consultants of the R-fMRI Network. All manuscripts and feedback will be freely available online with citable permanent URL for open-access. The goal of PRN is to supplement the “peer reviewed” journal publication system – by more rapidly communicating the latest research achievements throughout the world. We hope PRN will help the field to embrace the preprint model and thus further accelerate R-fMRI and neuroscience related studies, eventually enhancing human mental health.

Methods and utility of EEG-fMRI in epilepsy

van Graan, Louis André; Lemieux, Louis; Chaudhary, Umair Javaid
Fonte: AME Publishing Company Publicador: AME Publishing Company
Tipo: Artigo de Revista Científica
Publicado em /04/2015 Português
Relevância na Pesquisa
26.73%
Brain activity data in general and more specifically in epilepsy can be represented as a matrix that includes measures of electrophysiology, anatomy and behaviour. Each of these sub-matrices has a complex interaction depending upon the brain state i.e., rest, cognition, seizures and interictal periods. This interaction presents significant challenges for interpretation but also potential for developing further insights into individual event types. Successful treatments in epilepsy hinge on unravelling these complexities, and also on the sensitivity and specificity of methods that characterize the nature and localization of underlying physiological and pathological networks. Limitations of pharmacological and surgical treatments call for refinement and elaboration of methods to improve our capability to localise the generators of seizure activity and our understanding of the neurobiology of epilepsy. Simultaneous electroencephalography and functional magnetic resonance imaging (EEG-fMRI), by potentially circumventing some of the limitations of EEG in terms of sensitivity, can allow the mapping of haemodynamic networks over the entire brain related to specific spontaneous and triggered epileptic events in humans, and thereby provide new localising information. In this work we review the published literature...

Orthogonalization of Regressors in fMRI Models

Mumford, Jeanette A.; Poline, Jean-Baptiste; Poldrack, Russell A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 28/04/2015 Português
Relevância na Pesquisa
26.73%
The occurrence of collinearity in fMRI-based GLMs (general linear models) may reduce power or produce unreliable parameter estimates. It is commonly believed that orthogonalizing collinear regressors in the model will solve this problem, and some software packages apply automatic orthogonalization. However, the effects of orthogonalization on the interpretation of the resulting parameter estimates is widely unappreciated or misunderstood. Here we discuss the nature and causes of collinearity in fMRI models, with a focus on the appropriate uses of orthogonalization. Special attention is given to how the two popular fMRI data analysis software packages, SPM and FSL, handle orthogonalization, and pitfalls that may be encountered in their usage. Strategies are discussed for reducing collinearity in fMRI designs and addressing their effects when they occur.

Dimensionality of ICA in resting-state fMRI investigated by feature optimized classification of independent components with SVM

Wang, Yanlu; Li, Tie-Qiang
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 08/05/2015 Português
Relevância na Pesquisa
26.73%
Different machine learning algorithms have recently been used for assisting automated classification of independent component analysis (ICA) results from resting-state fMRI data. The success of this approach relies on identification of artifact components and meaningful functional networks. A limiting factor of ICA is the uncertainty of the number of independent components (NIC). We aim to develop a framework based on support vector machines (SVM) and optimized feature-selection for automated classification of independent components (ICs) and use the framework to investigate the effects of input NIC on the ICA results. Seven different resting-state fMRI datasets were studied. 18 features were devised by mimicking the empirical criteria for manual evaluation. The five most significant (p < 0.01) features were identified by general linear modeling and used to generate a classification model for the framework. This feature-optimized classification of ICs with SVM (FOCIS) framework was used to classify both group and single subject ICA results. The classification results obtained using FOCIS and previously published FSL-FIX were compared against manually evaluated results. On average the false negative rate in identifying artifact contaminated ICs for FOCIS and FSL-FIX were 98.27 and 92.34%...

Objective Bayesian fMRI analysis—a pilot study in different clinical environments

Magerkurth, Joerg; Mancini, Laura; Penny, William; Flandin, Guillaume; Ashburner, John; Micallef, Caroline; De Vita, Enrico; Daga, Pankaj; White, Mark J.; Buckley, Craig; Yamamoto, Adam K.; Ourselin, Sebastien; Yousry, Tarek; Thornton, John S.; Weiskopf,
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 12/05/2015 Português
Relevância na Pesquisa
26.73%
Functional MRI (fMRI) used for neurosurgical planning delineates functionally eloquent brain areas by time-series analysis of task-induced BOLD signal changes. Commonly used frequentist statistics protect against false positive results based on a p-value threshold. In surgical planning, false negative results are equally if not more harmful, potentially masking true brain activity leading to erroneous resection of eloquent regions. Bayesian statistics provides an alternative framework, categorizing areas as activated, deactivated, non-activated or with low statistical confidence. This approach has not yet found wide clinical application partly due to the lack of a method to objectively define an effect size threshold. We implemented a Bayesian analysis framework for neurosurgical planning fMRI. It entails an automated effect-size threshold selection method for posterior probability maps accounting for inter-individual BOLD response differences, which was calibrated based on the frequentist results maps thresholded by two clinical experts. We compared Bayesian and frequentist analysis of passive-motor fMRI data from 10 healthy volunteers measured on a pre-operative 3T and an intra-operative 1.5T MRI scanner. As a clinical case study...

Atlas-based head modeling and spatial normalization for high-density diffuse optical tomography: In vivo validation against fMRI

Ferradal, Silvina L.; Eggebrecht, Adam T.; Hassanpour, Mahlega; Snyder, Abraham Z.; Culver, Joseph P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.73%
Diffuse optical imaging (DOI) is increasingly becoming a valuable neuroimaging tool when fMRI is precluded. Recent developments in high-density diffuse optical tomography (HD-DOT) overcome previous limitations of sparse DOI systems, providing improved image quality and brain specificity. These improvements in instrumentation prompt the need for advancements in both i) realistic forward light modeling for accurate HD-DOT image reconstruction, and ii) spatial normalization for voxel-wise comparisons across subjects. Individualized forward light models derived from subject-specific anatomical images provide the optimal inverse solutions, but such modeling may not be feasible in all situations. In the absence of subject-specific anatomical images, atlas-based head models registered to the subject’s head using cranial fiducials provide an alternative solution. In addition, a standard atlas is attractive because it defines a common coordinate space in which to compare results across subjects. The question therefore arises as to whether atlas-based forward light modeling ensures adequate HD-DOT image quality at the individual and group level. Herein, we demonstrate the feasibility of using atlas-based forward light modeling and spatial normalization methods. Both techniques are validated using subject-matched HD-DOT and fMRI data sets for visual evoked responses measured in five healthy adult subjects. HD-DOT reconstructions obtained with the registered atlas anatomy (i.e. atlas DOT) had an average localization error of 2.7 mm relative to reconstructions obtained with the subject-specific anatomical images (i.e. subject-MRI DOT)...

fMRI measurements of amygdala activation are confounded by stimulus correlated signal fluctuation in nearby veins draining distant brain regions

Boubela, Roland N.; Kalcher, Klaudius; Huf, Wolfgang; Seidel, Eva-Maria; Derntl, Birgit; Pezawas, Lukas; Našel, Christian; Moser, Ewald
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 21/05/2015 Português
Relevância na Pesquisa
26.73%
Imaging the amygdala with functional MRI is confounded by multiple averse factors, notably signal dropouts due to magnetic inhomogeneity and low signal-to-noise ratio, making it difficult to obtain consistent activation patterns in this region. However, even when consistent signal changes are identified, they are likely to be due to nearby vessels, most notably the basal vein of rosenthal (BVR). Using an accelerated fMRI sequence with a high temporal resolution (TR = 333 ms) combined with susceptibility-weighted imaging, we show how signal changes in the amygdala region can be related to a venous origin. This finding is confirmed here in both a conventional fMRI dataset (TR = 2000 ms) as well as in information of meta-analyses, implying that “amygdala activations” reported in typical fMRI studies are likely confounded by signals originating in the BVR rather than in the amygdala itself, thus raising concerns about many conclusions on the functioning of the amygdala that rely on fMRI evidence alone.

From Spatial Regularization to Anatomical Priors in fMRI Analysis

Ou, Wanmei; Golland, Polina
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2005 Português
Relevância na Pesquisa
26.73%
In this paper, we study Markov Random Fields as spatial smoothing priors in fMRI detection. Relatively high noise in fMRI images presents a serious challenge for the detection algorithms, creating a need for spatial regularization of the signal. Gaussian smoothing, traditionally employed to boost the signal-to-noise ratio, often removes small activation regions. Recently, the use of Markov priors has been suggested as an alternative regularization approach. In this work, we investigate fast approximate inference algorithms for using MRFs in fMRI detection, propose a novel way to incorporate anatomical information into the detection framework, validate the methods through ROC analysis on simulated data and demonstrate their application in a real fMRI study.

Reduced fMRI activity predicts relapse in patients recovering from stimulant dependence

Clark, Vincent P.; Beatty, Gregory; Anderson, Robert E.; Kodituwakku, Piyadassa; Phillips, John; Lane, Terran D.R.; Kiehl, Kent A.; Calhoun, Vince D.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.73%
Relapse presents a major problem for patients recovering from stimulant dependence. Here we examined the hypothesis that patterns of brain function obtained at an early stage of abstinence differentiates patients who later relapse vs. those who remain abstinent. Forty-five recently abstinent stimulant-dependent patients were tested using a randomized event-related functional MRI (ER-fMRI) design that was developed in order to replicate a previous ERP study of relapse using a selective attention task, and were then monitored until 6 months of verified abstinence or stimulant use occurred. SPM revealed smaller absolute BOLD response amplitude in bilateral ventral posterior cingulate and right insular cortex in 23 patients positive for relapse to stimulant use compared with 22 who remained abstinent. ER-fMRI data was compared with psychiatric, neuropsychological, demographic, personal- and family- history of drug use in order to form predictive models, and was found to predict abstinence with higher accuracy than any other single measure obtained in this study. Logistic regression using fMRI amplitude in right posterior cingulate and insular cortex predicted abstinence with 77.8% accuracy, which increased to 89.9% accuracy when history of mania was included. Using 10-fold cross-validation...

RETROSPECTIVE DETECTION OF INTERLEAVED SLICE ACQUISITION PARAMETERS FROM FMRI DATA

Parker, David; Rotival, Georges; Laine, Andrew; Razlighi, Qolamreza R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
26.73%
To minimize slice excitation leakage to adjacent slices, interleaved slice acquisition is nowadays performed regularly in fMRI scanners. In interleaved slice acquisition, the number of slices skipped between two consecutive slice acquisitions is often referred to as the ‘interleave parameter’; the loss of this parameter can be catastrophic for the analysis of fMRI data. In this article we present a method to retrospectively detect the interleave parameter and the axis in which it is applied. Our method relies on the smoothness of the temporal-distance correlation function, which becomes disrupted along the axis on which interleaved slice acquisition is applied. We examined this method on simulated and real data in the presence of fMRI artifacts such as physiological noise, motion, etc. We also examined the reliability of this method in detecting different types of interleave parameters and demonstrated an accuracy of about 94% in more than 1000 real fMRI scans.

Role of the parahippocampal cortex in memory for the configuration but not the identity of objects: converging evidence from patients with selective thermal lesions and fMRI

Bohbot, Véronique D.; Allen, John J. B.; Dagher, Alain; Dumoulin, Serge O.; Evans, Alan C.; Petrides, Michael; Kalina, Miroslav; Stepankova, Katerina; Nadel, Lynn
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 03/08/2015 Português
Relevância na Pesquisa
26.73%
The parahippocampal cortex and hippocampus are brain structures known to be involved in memory. However, the unique contribution of the parahippocampal cortex remains unclear. The current study investigates memory for object identity and memory of the configuration of objects in patients with small thermo-coagulation lesions to the hippocampus or the parahippocampal cortex. Results showed that in contrast to control participants and patients with damage to the hippocampus leaving the parahippocampal cortex intact, patients with lesions that included the right parahippocampal cortex (RPH) were severely impaired on a task that required learning the spatial configuration of objects on a computer screen; these patients, however, were not impaired at learning the identity of objects. Conversely, we found that patients with lesions to the right hippocampus (RH) or left hippocampus (LH), sparing the parahippocampal cortex, performed just as well as the control participants. Furthermore, they were not impaired on the object identity task. In the functional Magnetic Resonance Imaging (fMRI) experiment, healthy young adults performed the same tasks. Consistent with the findings of the lesion study, the fMRI results showed significant activity in the RPH in the memory for the spatial configuration condition...

3D interactive tractography-informed resting-state fMRI connectivity

Chamberland, Maxime; Bernier, Michaël; Fortin, David; Whittingstall, Kevin; Descoteaux, Maxime
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 11/08/2015 Português
Relevância na Pesquisa
26.73%
In the past decade, the fusion between diffusion magnetic resonance imaging (dMRI) and functional magnetic resonance imaging (fMRI) has opened the way for exploring structure-function relationships in vivo. As it stands, the common approach usually consists of analysing fMRI and dMRI datasets separately or using one to inform the other, such as using fMRI activation sites to reconstruct dMRI streamlines that interconnect them. Moreover, given the large inter-individual variability of the healthy human brain, it is possible that valuable information is lost when a fixed set of dMRI/fMRI analysis parameters such as threshold values are assumed constant across subjects. By allowing one to modify such parameters while viewing the results in real-time, one can begin to fully explore the sensitivity of structure-function relations and how they differ across brain areas and individuals. This is especially important when interpreting how structure-function relationships are altered in patients with neurological disorders, such as the presence of a tumor. In this study, we present and validate a novel approach to achieve this: First, we present an interactive method to generate and visualize tractography-driven resting-state functional connectivity...

A client-server software application for statistical analysis of fMRI data

Choudhary, Vijay Singh, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 66 leaves; 2781086 bytes; 2780893 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
26.73%
Statistical analysis methods used for interrogating functional magnetic resonance imaging (fMRI) data are complex and continually evolving. There exist a scarcity of educational material for fMRI. Thus, an instructional based software application was developed for teaching the fundamentals of statistical analysis in fMRI. For wider accessibility, the application was designed with a client/server architecture. The Java client has a layered design for flexibility and a nice Graphical User Interface (GUI) for user interaction. The application client can be deployed to multiple platforms in heterogeneous and distributed network. The future possibility of adding real-time data processing capabilities in the server led us to choose CGI/Perl/C as server side technologies. The client and server communicates via a simple protocol through the Apache Web Server. The application provides students with opportunities for hands-on exploration of the key concepts using phantom data as well as sample human fMRI data. The simulation allows students to control relevant parameters and observe intermediate results for each step in the analysis stream (spatial smoothing, motion correction, statistical model parameter selection etc.). Eventually this software tool and the accompanying tutorial will be disseminated to researchers across the globe via Biomedical Informatics Research Network (BIRN) portal.; by Vijay Singh Choudhary.; Thesis (S.M.)--Massachusetts Institute of Technology...

Multimodal neuroimaging with simultaneous electroencephalogram and high-field functional magnetic resonance imaging; Multimodal neuroimaging with simultaneous EEG and high-field fMRI

Purdon, Patrick L. (Patrick Lee), 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 189 p.
Português
Relevância na Pesquisa
26.73%
Simultaneous recording of electroencephalogram (EEG) and functional magnetic resonance imaging (tMRI) is an important emerging tool in functional neuroimaging with the potential to reveal new mechanisms for brain function by combining the high spatial resolution of fMRI with the high temporal resolution of EEG. Applications for this technique include studies of sleep, epilepsy, and anesthesia, as well as basic sensory, perceptual, and cognitive processes. Unlike methods that combine these modalities from separate recordings, simultaneous recordings can reveal temporal correlations between EEG and fMRI. Simultaneous recordings also eliminate environmental confounds inherent with separate recordings. MRI systems produce electromagnetic interference that can corrupt sensitive electrophysiological recordings, making simultaneous recordings challenging. Gradient switching and RF pulses can saturate EEG amplifiers, and cardiac pulsation within the static magnetic field produces large artifact signals ("ballistocardiogram") that confound EEG analysis. In this Ph.D. thesis, we develop an EEG acquisition system compatible with fMRI at 3 and 7 Tesla, a method for eliminating the ballistocardiogram artifact using adaptive filtering, and use these methods to study the 40-Hz auditory steady-state response (ASSR). The adaptive filtering method outperforms existing standard methods by up to 600%. The ASSR is a sub-microvolt level auditory evoked potential related to sleep...

Metabolic Brain-Computer Interfaces; Metabolische Gehirn-Komputer Schnittstelle

Sitaram, Ranganatha
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
26.73%
Brain-Computer Interfaces (BCI) utilise neurophysiological signals originating in the brain to activate or deactivate external devices or computers (Donoghue 2002; Wolpaw, Birbaumer et al. 2002; Nicolelis 2003; Birbaumer and Cohen 2007). The neuronal signals can be recorded from inside the brain (invasive BCIs) or outside (non-invasive BCIs) of the brain. Most BCIs developed so far have used operant training of direct neuroelectric responses, Electroencephalography (EEG) waves, event-related potentials and brain oscillations (Birbaumer, Weber et al. 2006; Birbaumer and Cohen 2007). Compared to neuroelectric studies on regulation of brain activity, there have been fewer studies with metabolic signals from the brain (Sitaram, Caria et al. 2007; Weiskopf, Sitaram et al. 2007; Sitaram, Weiskopf et al. 2008). Near Infrared Spectroscopy (NIRS) and Functional magnetic resonance imaging (fMRI) present themselves as attractive methods of acquiring hemodynamic activity of the brain for a developing a BCI. In this study, we exploit NIRS and fMRI for the implementation of BCIs for the investigation of regulation of hemodynamic signals in the brain and their behavioural consequences. We propose that these methods could be used not only for communication and control in paralysis...

Neural Correlates of Perception for Action in Humans Using TMS and fMRI; Neuronale Korrelate der Perzeption zur Bewegungssteuerung beim Menschen untersucht mittels TMS und fMRI

Reichenbach, Alexandra
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
26.73%
Movements are humans interface to their social and physical environment. The human brain processes numerous complex computations during everyday actions, such as reaching for a door knob. It must recognize and localize the knob visually, and calculate its spatial relation to the hand. Then, the movement of the arm and hand with all their muscles has to be planned. During the movement, these parameters are monitored, and when the environment changes, for instance when the door is opened, the movement is adapted on the fly. Sensorimotor integration processes during a movement take 60-160ms, thus are much faster than processes for conscious perception. The mechanisms and cortical localization of these processes is the topic of the present dissertation. Perturbation paradigms are utilized for investigating reach adjustments: Participants have to reach for a target, and a perturbation, such as a displacement of the target, is introduced during the ongoing movement. Thus, the participant must adjust the movement, and the brain has to integrate the newly arriving sensory information into the current movement plan. The first project investigated the chronometry of the processes responsible for the integration of visual and proprioceptive information. I measured with electromyography (EMG) the neural latency from the perturbation to the response. This method provided the computation time necessary for integrating and transforming sensory to motor signals. Furthermore...

Neuronale Korrelate des Ironieverständnisses bei schizophrenen Patientinnen

Langohr, Karin
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
Português
Relevância na Pesquisa
26.73%
Defizite im Ironieverständnis bei schizophrenen Patienten gelten als experimentalpsychologisch gut belegt. Oft wird in diesem Zusammenhang vom schizophrenen Konkretismus gesprochen. Die neuronalen Grundlagen sind bisher jedoch unbekannt. Wiederholt wurde eine Fehlfunktion des cerebralen Theory-of-Mind-network vermutet, fMRT-Untersuchungen zur psychometrischen Schizotypie legen jedoch eher ein Defizit frontotemporaler Sprachperzeptionsregionen nahe. In dieser Studie wurde erstmalig das Ironieverständnis bei schizophrenen Patientinnen mittels ereigniskorrelierter funktioneller Kernspintomographie untersucht. Methoden: 15 Patientinnen mit Diagnose Schizophrenie und 15 gesunde Kontrollpersonen nahmen an der funktionell- kernspintomographischen Untersuchung zum prosodiefreien Ironieverständnis teil (3-T-Scanner, whole brain, 32 Schichten, TR= 2s, TE= 40 ms). Datenanalyse mit SPM5 Software. Direkt im Anschluss absolvierten diese und zusätzlich 24 gesunde Probandinnen eine offline-Version des Ironieverständnistests sowie einen Irony-Rating-Test, Sprichworttest und den Schizotypal-Personality-Questionnaire (SPQ). Während des fMRT-Experiments lasen die Teilnehmerinnen 44 kurze Situationen; Aufgabe war, zu verstehen, ob die darauf folgenden Aussagen ironisch (n=22) oder wörtlich (n=22) zu verstehen sind. In der Offline-Version des kernspintomographischen Paradigmas wurden diese um 10 sinnlose Aussage ergänzt und erfragt...

Real-time fMRI pattern decoding and neurofeedback using FRIEND: an FSL-integrated BCI toolbox

Sato, João R.; Basilio, Rodrigo; Paiva, Fernando Fernandes; Garrido, Griselda J.; Bramati, Ivanei E.; Bado, Patricia; Moll, Fernanda Tovar; Zahn, Roland; Moll, Jorge
Fonte: Public Library of Science - PLOS; San Francisco Publicador: Public Library of Science - PLOS; San Francisco
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.73%
The demonstration that humans can learn to modulate their own brain activity based on feedback of neurophysiological signals opened up exciting opportunities for fundamental and applied neuroscience. Although EEG-based neurofeedback has been long employed both in experimental and clinical investigation, functional MRI (fMRI)-based neurofeedback emerged as a promising method, given its superior spatial resolution and ability to gauge deep cortical and subcortical brain regions. In combination with improved computational approaches, such as pattern recognition analysis (e.g., Support Vector Machines, SVM), fMRI neurofeedback and brain decoding represent key innovations in the field of neuromodulation and functional plasticity. Expansion in this field and its applications critically depend on the existence of freely available, integrated and user-friendly tools for the neuroimaging research community. Here, we introduce FRIEND, a graphic-oriented user-friendly interface package for fMRI neurofeedback and real-time multivoxel pattern decoding. The package integrates routines for image preprocessing in real-time, ROI-based feedback (single-ROI BOLD level and functional connectivity) and brain decoding-based feedback using SVM. FRIEND delivers an intuitive graphic interface with flexible processing pipelines involving optimized procedures embedding widely validated packages...

Seeking the neural basis of grammar : English noun and verb morphological processing investigated with rapid event-related fMRI and intracortical electrophysiology

Sahin, Nedim T. (Nedim Turan), 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (271 leaves); 21714406 bytes; 21749390 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
26.73%
(cont.) the functionality of the fMRI data analysis and visualization tools used at Massachusetts General Hospital. I analyze and interpret an 18-subject fMRI experiment I ran using the new task design and software tools. Finally, I present preliminary findings on linguistic questions as well as the nature of fMRI signal, using direct Electrophysiological data recorded from electrodes implanted in the brains of two Epilepsy patients. These patients had electrodes implanted through or near classical language areas of their brains, as a necessary clinical step in locating and surgically removing the seizure-causing tissue. The main findings of this thesis are: 1.) Morphology alone can activate Broca's area, 2.) Other areas are involved, including BA47, anterior insula, and SMA, 3.) Broca's area and BA47 respond to application of abstract grammatical features, even without phonological manipulations, 4.) Morphophonological manipulation additionally recruits insula and SMA, 5.) While simply accessing nouns versus verbs may involve separable brain regions, inflectional processing of the two categories may be done by the same process, 6.) Regularly and Irregularly inflected verbs show a double dissociation of activation in frontal and medial regions...

Transient brain activity disentangles fMRI resting-state dynamics in terms of spatially and temporally overlapping networks

Karahanoğlu, Fikret Işik; Van De Ville, Dimitri
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.73%
Dynamics of resting-state functional magnetic resonance imaging (fMRI) provide a new window onto the organizational principles of brain function. Using state-of-the-art signal processing techniques, we extract innovation-driven co-activation patterns (iCAPs) from resting-state fMRI. The iCAPs' maps are spatially overlapping and their sustained-activity signals temporally overlapping. Decomposing resting-state fMRI using iCAPs reveals the rich spatiotemporal structure of functional components that dynamically assemble known resting-state networks. The temporal overlap between iCAPs is substantial; typically, three to four iCAPs occur simultaneously in combinations that are consistent with their behaviour profiles. In contrast to conventional connectivity analysis, which suggests a negative correlation between fluctuations in the default-mode network (DMN) and task-positive networks, we instead find evidence for two DMN-related iCAPs consisting the posterior cingulate cortex that differentially interact with the attention network. These findings demonstrate how the fMRI resting state can be functionally decomposed into spatially and temporally overlapping building blocks using iCAPs.