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Diving into the depth of primary motor cortex: a high-resolution investigation of the motor system using 7Tesla fMRI

Amado, Catarina Pereira
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2014 Português
Relevância na Pesquisa
36.54%
Dissertação para a obtenção do Grau de Mestre em Engenharia Biomédica; Human behaviour is grounded in our ability to perform complex tasks. While human motor function has been studied for over a century the cortical processes underlying motor behaviour are still under debate. Central to the execution of action is the primary motor cortex (M1), which has previously been considered to be responsible for the execution of movements planned in the premotor cortex, yet recent studies point to more complex roles for M1 in orchestrating motor-related information. The purpose of this project is to study the functional properties of primary motor cortex using ultra-high fMRI. The spatial resolution made possible by using a high field magnet allows us to investigate novel questions such as the existence of cortical columns, the functional organization pattern for single fingers and functional involvement of M1 in motor imagery and observation. Thirteen young healthy subjects participated in this study. Functional and anatomical high resolution images were acquired. Four functional scans were acquired for the different tasks: motor execution; motor imagery; movement observation and rest. The paradigm used was a randomized finger tapping. The images analysis was performed with the Brainvoyager QX program. Using the novel high resolution cortical grid sampling analysis tools...

Cortical brain regions associated with color processing: an FMRI study

Bramão, Inês; Faísca, Luís; Forkstam, Christian; Reis, Alexandra; Petersson, Karl Magnus
Fonte: Bentham Open Publicador: Bentham Open
Tipo: Artigo de Revista Científica
Publicado em //2010 Português
Relevância na Pesquisa
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To clarify whether the neural pathways concerning color processing are the same for natural objects, for artifacts objects and for non-objects we examined brain responses measured with functional magnetic resonance imaging (FMRI) during a covert naming task including the factors color (color vs. black&white (B&W)) and stimulus type (natural vs. artifacts vs. non-objects). Our results indicate that the superior parietal lobule and precuneus (BA 7) bilaterally, the right hippocampus and the right fusifom gyrus (V4) make part of a network responsible for color processing both for natural objects and artifacts, but not for non-objects. When color objects (both natural and artifacts) were contrasted with color non-objects we observed activations in the right parahippocampal gyrus (BA 35/36), the superior parietal lobule (BA 7) bilaterally, the left inferior middle temporal region (BA 20/21) and the inferior and superior frontal regions (BA 10/11/47). These additional activations s uggest that colored objects recruit brain regions that are related to visual semantic information/retrieval and brain regions related to visuo-spatial processing. Overall, the results suggest that color information is an attribute that can improve object recognition (behavioral results) and activate a specific neural network related to visual semantic information that is more extensive than for B&W objects during object recognition

Variable fMRI activation during two different language tasks in a patient with cognitive delay

Escorsi-Rosset,Sara; Wichert-Ana,Lauro; Bianchin,Marino Muxfeldt; Velasco,Tonicarlo Rodrigues; Sakamoto,Américo C.; Leite,João Pereira; Santos,Antonio Carlos; Araújo,Dráulio Barros de
Fonte: Academia Brasileira de Neurologia - ABNEURO Publicador: Academia Brasileira de Neurologia - ABNEURO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2007 Português
Relevância na Pesquisa
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Functional MRI produces a more accurate localization of the language areas for epilepsy surgery purpose, but requires the patient cooperation. We report a 34 years-old woman with mental retardation who underwent two different verbal fluency tasks, category and word naming. We found a strong activation of the Broca’s area in the most difficult task. We suggest that a multi-task fMRI study could be successful in patients with cognitive delay.

Brain activation for reading and listening comprehension: an fMRI study of modality effects and individual differences in language comprehension

Buchweitz,Augusto; Mason,Robert A.; Tomitch,Lêda M. B.; Just,Marcel Adam
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 01/12/2009 Português
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The study compared the brain activation patterns associated with the comprehension of written and spoken Portuguese sentences. An fMRI study measured brain activity while participants read and listened to sentences about general world knowledge. Participants had to decide if the sentences were true or false. To mirror the transient nature of spoken sentences, visual input was presented in rapid serial visual presentation format. The results showed a common core of amodal left inferior frontal and middle temporal gyri activation, as well as modality specific brain activation associated with listening and reading comprehension. Reading comprehension was associated with more left-lateralized activation and with left inferior occipital cortex (including fusiform gyrus) activation. Listening comprehension was associated with extensive bilateral temporal cortex activation and more overall activation of the whole cortex. Results also showed individual differences in brain activation for reading comprehension. Readers with lower working memory capacity showed more activation of right-hemisphere areas (spillover of activation) and more activation in the prefrontal cortex, potentially associated with more demand placed on executive control processes. Readers with higher working memory capacity showed more activation in a frontal-posterior network of areas (left angular and precentral gyri...

Hippocampal-cerebellar involvement in enhancement of performance in word-based BRT with the presence of background noise: an initial fMRI study

Manan,Hanani Abdul; Franz,Elizabeth A.; Yusoff,Ahmad Nazlim; Mukari,Siti Zamratol-Mai Sarah
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 01/12/2012 Português
Relevância na Pesquisa
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Background noise may impose deleterious effects on cognitive processing. However, noise below the threshold level may increase the ability to detect stimuli via stochastic resonance mechanisms (SR). The present study investigates whether task performance is deteriorated or enhanced by 5-dB SNR and, if the task performance is enhanced, whether this facilitation in performance points to a particular neural area that serves to attenuate noise and/or increase effective task performance. The areas of interest are the cerebellum and hippocampus due to their roles in working memory (WM) and their links with attention. Fifteen healthy young Malay adults performed three tasks during fMRI scanning: listening to babble noise (N), WM task in quiet (WMQ), and WM task in noise (WMN). Activated regions during N are bilateral STG and MTG. Both WM tasks produced similar activation in a network of areas in the frontal, temporal and parietal lobes. However, the two tasks demonstrated marked differences in the left hippocampus, right posterior cerebellum, and bilateral anterior cerebellum. Moreover, the results obtained from the behavioral task demonstrated that participants responded better in the presence of noise. These results support the hypothesis that the left hippocampus...

Processing of affective faces varying in valence and intensity in shy adults: an event-related fMRI study

Tatham,Erica L.; Schmidt,Louis A.; Beaton,Elliott A.; Schulkin,Jay; Hall,Geoffrey B.
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
36.54%
Recent behavioral and electrocortical studies have found that shy and socially anxious adults are hypersensitive to the processing of negative and ambiguous facial emotions. We attempted to extend these findings by examining the neural correlates of affective face processing in shy adults using an event-related fMRI design. We presented pairs of faces that varied in affective valence and intensity. The faces were morphed to alter the degree of intensity of the emotional expressive faces. Twenty-four (12 shy and 12 non-shy) young adult participants then made same/different judgments to these faces while in an MR scanner. We found that shy adults exhibited greater neural activation across a distinct range of brain regions to pairs of faces expressing negative emotions, moderate levels of emotional intensity, and emotional faces that were incongruent with one another. In contrast, non-shy individuals exhibited greater neural activation across a distinct range of brain regions to pairs of faces expressing positive emotions, low levels of emotional intensity, and emotional faces that were congruent with one another. Findings suggest that there are differences in neural responses between shy and non-shy adults when viewing affective faces that vary in valence...

Resting state fMRI reveals a default mode dissociation between retrosplenial and medial prefrontal subnetworks in ASD despite motion scrubbing

Starck, Tuomo; Nikkinen, Juha; Rahko, Jukka; Remes, Jukka; Hurtig, Tuula; Haapsamo, Helena; Jussila, Katja; Kuusikko-Gauffin, Sanna; Mattila, Marja-Leena; Jansson-Verkasalo, Eira; Pauls, David L.; Ebeling, Hanna; Moilanen, Irma; Tervonen, Osmo; Kiviniemi,
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
In resting state functional magnetic resonance imaging (fMRI) studies of autism spectrum disorders (ASDs) decreased frontal-posterior functional connectivity is a persistent finding. However, the picture of the default mode network (DMN) hypoconnectivity remains incomplete. In addition, the functional connectivity analyses have been shown to be susceptible even to subtle motion. DMN hypoconnectivity in ASD has been specifically called for re-evaluation with stringent motion correction, which we aimed to conduct by so-called scrubbing. A rich set of default mode subnetworks can be obtained with high dimensional group independent component analysis (ICA) which can potentially provide more detailed view of the connectivity alterations. We compared the DMN connectivity in high-functioning adolescents with ASDs to typically developing controls using ICA dual-regression with decompositions from typical to high dimensionality. Dual-regression analysis within DMN subnetworks did not reveal alterations but connectivity between anterior and posterior DMN subnetworks was decreased in ASD. The results were very similar with and without motion scrubbing thus indicating the efficacy of the conventional motion correction methods combined with ICA dual-regression. Specific dissociation between DMN subnetworks was revealed on high ICA dimensionality...

Neural representation of conceptual knowledge in schizophrenic patients. An fMRI study.; Neuronale Repräsentation von semantischem Wissen in schizophrenen Patienten. Eine fMRT-Studie.

Holzwarth, Dorothea Anne
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.54%
Neural representation of conceptual knowledge in healthy subjects has already been investigated by lesion studies, as well as by functional neuro-imaging experiments, resulting in the implementation of mainly three different theories to explain the obtained data. Here, we investigate the representation of semantic concepts by studying the processing of “living” and “non-living” categories in schizophrenic patients, as compared to healthy controls. Distinction between “living” and “nonliving” constitutes an important aspect of social cognition where schizophrenic patients are impaired. We used a set of complex and naturalistic stimuli from a standardized picture data base (IAPS) to compare the differential brain activation induced by different categorical stimuli (humans, animals, food, tools). 11 schizophrenic patients and 15 healthy controls were measured with fMRI while watching the pictorial stimuli and performing a categorization task (discrimination between “living” and “nonliving” stimuli which were presented in a randomized order). A fronto-parietal network comprising orbito-frontal regions and regions at the occipito-temporal junction, as well as the superior temporal sulcus (STS) was found to be more strongly activated by “living” stimuli (human...

Die Rolle der Basalganglien zur Perzeption von Gesten - Erfassungen mit fMRT und PET; The role of the basalganglia to the perception of gestures - investigations with fMRI and PET

Heymans, Ulrike
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.54%
In dieser Arbeit wurde die Rolle der Basalganglien in der Gestikerkennung mit Hilfe eines multimodalen Ansatzes untersucht. Um die spezifische Rolle der Basalganglien zu beleuchten, wurde Parkinson Patienten im Vergleich zu einer altersangepassten Kontrollgruppe Videomaterial mit unterschiedlichen Arten von Bewegungen (isolierte Handbewegungen, nicht-emotionale körperbezogene Bewegungen und Ausdrucksgesten) gezeigt, während die BOLD-Aktivität (Blood Oxygenation Level Dependent contrast) im Kernspintomographen gemessen wurde. Um Aussagen darüber treffen zu können, in wieweit die Unterschiede zwischen den beiden Gruppen spezifisch für die Parkinsonerkrankung bzw. für die damit einhergehenden Veränderungen in den Basalganglien ist, korrelierten wir die fMRT-Ergebnsisse und Fehleranzahl in der Gestikerkennung mit einer PET - Messung der Dopamintransporterverfügbarkeit (DAT) im Putamen mit [11C]d-threo-methylphenidate sowie den klinischen Parametern (UPDRS, Hoehn und Yahr scale). Das Striatum ist über mehrere parallele Schleifen mit temporalen, limbischen und präfrontalen Arealen verbunden, die bei gesunden Probanden in die Gestik- und Gesichtererkennung eingebunden sind. Die Patienten zeigten durchschnittlich eine um 26% herabgesetzte Dopamintransporterverfügbarkeit gegenüber den alterskorrigierten gesunden Kontrollen. Diese Verminderung korrelierte nicht nur mit der klinischen Symptomatik der Patienten sondern auch mit der Fehleranzahl in der Gestikerkennung. Diese Veränderungen gingen mit einer verminderten Aktivität im Putamen gegenüber den gesunden Probanden während der Präsentation aller drei Arten von Bewegungen einher...

Zentralnervöse Verarbeitung von essensrelevanten Reizen bei Patienten mit Diabetes mellitus Typ 2 – eine fMRT-Studie; Neural resposes to food stimuli in patients with type 2 diabetes – a fMRI study

Klamer, Silke
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.54%
Diabetes mellitus Typ 2 wird aufgrund weltweit zunehmender Inzidenz bereits in naher Zukunft eine der führenden Ursachen von Morbidität und Mortalität darstellen. Das Risiko diabetesassoziierter Folgeerkrankungen kann jedoch durch eine erfolgreiche Modifikation der Essgewohnheiten anhand spezifischer Ernährungsempfehlungen reduziert werden. Allerdings haben viele Patienten Schwierigkeiten, diese Diätvorschriften dauerhaft einzuhalten. Bereits bei Gesunden führen eine temporäre Essensdeprivation und restriktive Diät zu einer Veränderung des positiven Verstärkungswertes von Nahrung. Die Auswirkungen der lebenslangen Diät auf Patienten mit Diabetes mellitus Typ 2 (T2DM) sind bislang jedoch nur wenig erforscht. Daher haben wir mittels fMRT die zerebrale Verarbeitung visuell präsentierter Essensstimuli bei Patienten mit Diabetes mellitus Typ 2 im Vergleich zu gesunden Kontrollpersonen untersucht und diese Ergebnisse mit Untersuchungen hinsichtlich des Appetitgefühls, der der Nahrungsaufnahme zugrunde liegenden motivationalen Faktoren, sowie des Einhaltens der Ernährungsempfehlungen und der eigenen Zuversicht diesbezüglich kombiniert. Die Ergebnisse zeigen, dass Personen mit T2DM eine verstärkte Antwort auf essensrelevante Stimuli in Insula...

Human visual processing of natural facial motion analyzed by fMRI; Die menschliche visuelle Verarbeitung von natürlichen Gesichtsbewegungen - untersucht mit fMRI

Brockhaus, Matthias
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.65%
Psychological studies have shown strong evidence that facial motion supports identification of faces. Until now, the sensitivity to moving faces in brain regions thought to process identity information was not well known. The present thesis studied how the brain processes natural non-rigid facial motion in direct comparison to static face stimuli. A previous study by Schultz and Pilz (2009) showed that dynamic faces elicit higher responses than static faces in lateral temporal areas (hMT/V5 and STS). Interestingly, that study showed that staticface-sensitive regions FFA and OFA also respond more to dynamic than static faces. The current study pursues this work to exclude potential confounding factors. Previous results were confirmed and specified: In order for this response increase to appear, a correct temporal order of the frames constituting the dynamic face stimuli is required. These results suggest cortical integration of facial motion and identity information and therefore link knowledge about cortical functioning with psychological experiments. For further investigation we suggest to examine a hypothesized transmission of dynamic facial signature information from motion-sensitive areas to the ventral temporal cortex.; Menschen sind hochspezialisierte soziale Wesen auf der Grundlage der Fähigkeit...

Kombinierte Untersuchung von sprachlichen und visuell-räumlichen Funktionen: eine zweifach-nutzbare Aufgabe für pädiatrische fMRT-Studien; Assessing language and visuospatial functions with one task: a "dual use" approach to performing fMRI in children

Ebner, Kathina Anna
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.65%
Die funktionelle Magnetresonanztomographie (fMRT) ist in der Klinik und in den Neurowissenschaften zu einer wichtigen, jedoch im Kindesalter noch schwierig anzuwendenden Methode geworden. In der Literatur ist gut belegt, dass eine Verkürzung der Untersuchungszeit die Rate erfolgreicher funktioneller Bildgebungsstudien bei Kindern erhöht. Ein Ansatz, die Untersuchungszeit zu verkürzen, wäre, zwei kognitive Funktionen mit nur einer Aufgabe zu untersuchen. Die Hypothese dieser Studie war, dass in der Kontrollbedingung einer bereits etablierten, kinderfreundlichen Sprachaufgabe (Vokal-Identifikations-Aufgabe, VIT) visuell-räumliche Funktionen benötigt werden. Somit könnte die Aufgabe als zweifach nutzbare Aufgabe eingesetzt werden, um sprachliche (Aktive Bedingung>Kontrollbedingung, AB>KB) und visuell-räumliche Funktionen (KB>AB) zu untersuchen. Für die Studie wurden 43 Kinder (12,0 ± 2,6 Jahre; 19 w) rekrutiert. Sie bearbeiteten den VIT, der aus der aktiven Bedingung (“Kommt im Namen des [visuell präsentierten] Objekts ein /i:/ vor?“) und der Kontrollbedingung (“Passt das kleinere [nicht benennbare, komplexe] Muster wie ein Puzzlestück in das größere?“) besteht, sowie eine visuell-räumliche Referenzaufgabe (Visuelle-Such-Aufgabe...

Approaching the Negative is not Avoiding the Positive: FNIRS, ERP and fMRI Studies on the Approach-Avoidance Task; Negatives annähern ist nicht dasselbe wie Positives vermeiden: FNIRS, EKP und fMRT Studien mit dem Approach-Avoidance Task

Ernst, Lena
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.65%
Approaching positive and avoiding negative stimuli are fundamental principles of behaviour. The Approach-Avoidance Task (AAT) assesses both automatic, compatible reactions (avoid negative, approach positive) as well as their regulation in incompatible conditions (approach negative, avoid positive). So-called stimulus response compatibility effects (SRC effects) denote enhanced reaction times (RTs) in incompatible compared to compatible conditions. Here, in 6 studies, the neuronal (fNIRS, fMRI) and neuropsychological (ERPs) correlates of such SRC effects were investigated in healthy persons reacting to positive and negative IAPS pictures. Most relevant were the following findings: For negative pictures, analyses revealed the mechanism of controlled attention allocation (P3 ERP) to mediate the relation between the personality trait goal-oriented pursuit and behaviour: Stronger willingness to actively regulate behavioural responses was associated with higher controlled attention allocation to the incompatible compared to the compatible condition and – thereby – with less automatic avoidance tendencies in response to negative pictures, i.e., with higher efficiency of regulation. Furthermore, an ad hoc developed, cued GoNoGo AAT variant was combined with fMRI: The cue event indicated participants to prepare a response...

Variational Bayesian causal connectivity analysis for fMRI

Luessi, Martin; Babacan, S. Derin; Molina Soriano, Rafael; Booth, James R.; Katsaggelos, Aggelos K.
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
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.

Neural substrates of 2D/3D object perception: a combined EEG/fMRI approach

Castelhano, João Miguel Seabra
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.65%
Perceptual decision making is defined as the choice of possible interpretations of the world based on the incoming sensory evidence. The role of temporal coding in this process and coherent perception, defined as hierarchical grouping of local elements, remains controversial. Oscillatory processes in the gamma frequency range (>30 Hz) have been proposed to play a role in signaling emerging object percepts in the brain. Studies using Electroencephalography and Magnetoencephalography (EEG and MEG) have suggested that gamma-band oscillations are related to the integration of information and the ability to form coherent gestalts as well as attention and working memory processes. It is accepted that gamma-band synchrony reflects binding of information across different brain regions leading to the emergence of a coherent percept. There are also reports that correlate gamma activity with many other cognitive processes. Hence, a wide variety of gamma-band patterns and sources were reported for different tasks. In this line, both animal and human studies have suggested that understanding oscillatory activity patterning can be important to understand normal and abnormal cognitive function. However, it remains unclear whether distinct patterns across the gamma frequency range related to different cognitive modules do coexist in the same task. We investigated visual perceptual recognition moments based on EEG analysis with ambiguous Mooney stimuli (black and white incomplete pictures). We departed from classical paradigms which are based on contrasts between stimuli conditions that are fixed in time...

Using Self-Organizing Maps to discover functional relationships of brain areas from fMRI images

O'Driscoll, Patrick
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text Formato: application/pdf
Português
Relevância na Pesquisa
36.65%
This thesis combines a Conscious Self-Organizing Map (SOM) with an interactive clustering method to analyze functional Magnetic Resonance Imaging (fMRI) data to produce improved brain maps compared to maps produced at The Methodist Hospital and in the literature focusing on similar problems. My new maps exhibit an increased level of symmetry, contiguity, coincidence with functional region, and more complete mapping of functional regions. The examined fMRI data contains brain activations of a subject repeatedly executing willed motion in response to a visual stimulus. Clustering the data from this experiment first determines the optimal preprocessing steps for cluster extraction, and second proves that the Conscious SOM provides a valid brain map that identifies interacting brain regions during the sequence of willed motion. I determined that the geometric rectification, motion correction, temporal smoothing, and normalization preprocessing steps facilitate the best clustering.

Investigating cognitive impairments in amyotrophic lateral sclerosis (ALS) using eye movements and functional magnetic resonance imaging (fMRI)

Witiuk, Kelsey
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.65%
Patients with Amyotrophic lateral sclerosis (ALS) often experience cognitive impairment that accompanies degeneration of the motor system. A valuable tool for assessing cognitive control over behaviour is the antisaccade task which requires: 1) inhibition of the automatic response to look towards an eccentric visual stimulus (prosaccade) to instead 2) redirect gaze in the opposite direction of the stimulus (antisaccade). Psychometric tests were used to quantify the degree of impairment, while eye tracking, functional magnetic resonance imaging (fMRI) and structural MRI were combined to identify the neural correlates of cognitive impairment in ALS. We predict ALS patients will have executive dysfunction and grey matter loss in executive and oculomotor control areas that will affect antisaccade performance and will alter the corresponding brain activation. ALS patients and age-matched controls participated in a rapid-event-related fMRI design with interleaved pro- and antisaccade trials. Catch trials (no stimulus presented after instructional cue to prepare pro- or antisaccade) allowed us to discern the preparatory period from the execution period. ALS patients were biased towards automatic saccade responses, and had greater difficulty with antisaccades relative to controls in terms of correct and timely responses. We found that worsened antisaccade performance in ALS correlated with the degree of cognitive impairment. Generally...

An fMRI study of emotional episodic memory in schizophrenia : effects of diagnosis and sex

Lakis, Nadia
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
36.65%
La schizophrénie est une psychopathologie largement hétérogène caractérisée entre autres par d’importantes défaillances dans le fonctionnement cognitif et émotionnel. En effet, par rapport à la population générale, forte proportion de ces individus présentent une mémoire déficitaire pour les événements émotionnels. À ce jour, le peu d’études qui se sont penchées sur la mémoire émotionnelle épisodique dans la schizophrénie, ont uniquement mis l’emphase sur l'effet de la valence des stimuli (c’est-à-dire le caractère agréable ou désagréable du stimulus). Toutefois, aucune n’a investigué spécifiquement l’intensité de la réaction aux stimuli (c’est-à-dire une faible par rapport à une forte réaction) malgré quantité de preuves faisant montre, dans la population générale, de différents processus de mémoire émotionnelle pour des stimuli suscitant une forte réaction par rapport à ceux évoquant une faible réponse. Ce manque est d’autant plus flagrant étant donné le nombre d’études ayant rapporté un traitement et un encodage atypiques des émotions spécifiquement au niveau de l’intensité de la réponse subjective chez des patients atteints de schizophrénie. Autre fait important...

Longitudinal assessment of neural activity in Parkinson’s disease with mild cognitive impairment using task based fMRI

Al-Azzawi, Mohamed Salah
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
36.65%
La maladie de Parkinson (PD) a été uniquement considérée pour ses endommagements sur les circuits moteurs dans le cerveau. Il est maintenant considéré comme un trouble multisystèmique, avec aspects multiples non moteurs y compris les dommages intérêts pour les circuits cognitifs. La présence d’un trouble léger de la cognition (TCL) de PD a été liée avec des changements structurels de la matière grise, matière blanche ainsi que des changements fonctionnels du cerveau. En particulier, une activité significativement réduite a été observée dans la boucle corticostriatale ‘cognitive’ chez des patients atteints de PD-TCL vs. PD non-TCL en utilisant IRMf. On sait peu de cours de ces modèles fonctionnels au fil du temps. Dans cette étude, nous présentons un suivi longitudinal de 24 patients de PD non démente qui a subi une enquête neuropsychologique, et ont été séparés en deux groupes - avec et sans TCL (TCL n = 11, non-TCL n = 13) en fonction du niveau 2 des recommandations de la Movement Disrders Society pour le diagnostic de PD-TCL. Ensuite, chaque participant a subi une IRMf en effectuant la tâche de Wisconsin pendant deux sessions, 19 mois d'intervalle. Nos résultats longitudinaux montrent qu'au cours de la planification de période de la tâche...

Multifocal fMRI mapping of visual cortical areas

Vanni, S; Henriksson, L.; James, Andrew
Fonte: Academic Press Publicador: Academic Press
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.65%
The multifocal mapping of electroretinograms and visual evoked potentials has established an important role in both basic research and in diagnostic procedures. We have developed a multifocal mapping method for fMRI, which allows detailed analysis of multiple local visual field representations in the cortex with excellent spatial resolution. Visual field was divided into 60 regions in a dartboard configuration, scaled according to the human magnification factor. Within blocks of 7 s, half of the regions were stimulated with checkerboard patterns contrast reversing at 8 reversals per second, while the other half remained inactive at uniform luminance. The subset of active regions changed with each 7-s block, according to an orthogonal design. Functional MRI was done with a 3-T GE Signa and analyzed with SPM2. A general linear model was fitted producing activation maps for each of the 60 regions, and local signal changes were quantified from V1. These activation maps were next assigned to 3D surface models of the cortical sheet, and then unfolded, using the Brain à la Carte software package. Phase-encoded retinotopic analysis of conventional design served as qualitative comparison data. With multifocal fMRI, all regions were mapped with good signal-to-noise ratio in V1...