| Popis: |
Attention is a crucial brain function for selectively processing behaviorally relevant stimuli over irrelevant ones. Several decades of psychophysical and neurophysiological studies have established that attention is highly dynamic and flexible, yet the mechanism underlying such flexible functionality remains unknown. In this thesis, we focus on the circuit and functional mechanisms of visual attention. We first investigate the flexible corticocortical communication mechanism by using a biophysically realistic large-scale circuit model consisting of sensory and association areas. We illustrate that spiking activity patterns with complex spatiotemporal dynamics emerging in both areas exhibit dynamically coordinated interactions, based on which the flexible gamma synchrony-based and subspace-based interareal communication can naturally emerge. We further demonstrate that such dynamic communication can be modulated during attention tasks and such modulated communication provides a mechanistic account for a great variety of neural effects of attention. We then apply this large-scale circuit model to attention-guided visual search, and illustrate that the interactions of bottom-up object saliency and top-down attention modulate the dynamics of spiking activity patterns; the modulation process can explain the hallmarks of neural and behavioral features of visual search, including the linear increase of reaction time with the number of search items. Finally, we identify a dynamical working regime of the visual cortex, in which a great variety of neural dynamics at the individual neuron and circuit levels can be reconciled and explained; these include super-Poisson spiking variability, theta-gamma coupling, and normalization. |
