Seminário em Neurociências 2011.2


Segunda-feira 19/12/2011 10:50h Anfiteatro 4 – Escola de Ciência e Tecnologia

Interareal directed interactions and their modulation by selective attention assessed with high density electrocorticography in monkey

Andre Bastos (Donders Institute, Radboud University Nijmegen, The Netherlands)


Behaviorally relevant stimuli are processed in visual cortex at the expense of irrelevant ones. The selection of relevant stimuli and the allocation of selective attention require parietal and frontal regions. Yet, it is not fully understood how these areas convey their selection to visual areas. The selection needs to flexibly implement appropriate patterns of interactions in visual cortex. Such flexible interactions might be subserved by flexible patterns of neuronal synchronization. To test this possibility, we trained two monkeys to perform a selective attention task. During fixation, two gratings were presented in the two hemifields. On a given trial, one of them was the behaviorally relevant target. We recorded local field potentials with a subdural electrocorticography (ECoG) grid that contained 252 electrodes, spaced at 2-3 mm, covering large expanses of the left hemisphere from V1 through V4, parietal and central cortex up to frontal eye field (FEF). Coherence and Granger Causality analyses revealed networks with spatially and spectrally distinct synchronization patterns. Areas V1 and V4 were synchronized in the gamma-frequency band (50-90 Hz) and this interaction was almost unidirectional from V1 to V4. Attention to a contralateral stimulus enhanced this feedforward gamma-band influence. Parietal cortex was synchronized with both V4 and with FEF in the beta frequency band. Between parietal cortex and V4, this interaction was predominantly from parietal to V4. For many V4-parietal electrode pairs, selective attention modulated and often enhanced the interaction. We propose that these two spatially and spectrally segregated networks interact to coordinate executive signals from the parietal and prefrontal cortices with perceptual processing in visual cortex.


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Notícia cadastrada em: 12/12/2011 13:36
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