Desenvolvimento de uma tecnica multimodal associando eletroencefalografia e imagens funcionais po ressonancia magnetica para o estudo de memoria operacional : aplicação em individuos com epilepsia de lobo temporal mesial associada a atrofia hipocampal

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

In this work, a multimodal approach involving electroencefalography (EEG) and functional Magnetic Resonance Imaging (fMRI) was implemented in order to perform studies on working memory in a group of subjects including controls and patients with mesial temporal lobe epilepsy (MTLE) associated with left hippocampal atrophy. In order to do that, a series of memory tests were implemented. These tests were based on a block paradigm containing epochs of memory codification and memory retention, optimized with respect to the time to fit both analysis of EEG and fMRI. The paradigm was presented to subjects for the first time during EEG acquisition and later during fMRI acquisition. EEG data indicated the presence of theta oscillations (4-8 Hz) in the frontal region and alpha oscillations (9-12 Hz) in the parieto-occipital region, in both groups. In the retention period, it was only observed the presence of the alpha rhythm in the posterior region, involving mainly the temporo-parietal regions. Diÿerently from what is found in the literature, correlations were established among these rhythms and both, positive and negative BOLD responses, but in diÿerent regions. Activation and deactivation zones were detected for all epochs. The deactivation zones were found not only in the neighborhood of the activation regions, but frequently in the homologous regions. Although both groups, controls and patients, presented similar performance for the memory tests, there were discrepancies between these groups in terms of the cortical structures involved in the memory task. In the control group, it was found predominance of activation at the left hemisphere whereas for the patient group activation was predominantly lateralized to the right, probably due to damage in the mesial temporal lobe structures. Such a finding is suggestive of the neuroplasticity phenomenon by which additional cortical areas would be recruited to compensate the structures affected by atrophy

ASSUNTO(S)

epilepsia do lobo temporal mesial mesial temporal lobe epilepsy functional magnetic resonance imaging imagem funcional de ressonancia magnetica eletroencefalografia memoria operacional working memory electroencephalography

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