The brain networks involved in orienting spatial attention have been elucidated to some extent. Just how these networks accomplish orienting, however, is still under investigation. It is proposed that neural synchronization plays an important role in the organization and function of these networks. I will describe some recent results from my laboratory that begin to describe the temporal dynamics within the dorsal network of brain regions that orients voluntary attention. Presentation of a cue as to where in space a target stimulus will occur begins a cascade of processes that involves synchronization of frontal and parietal regions with each other, and of parietal regions with sensory cortex, as well as changes in synchronization within those areas. Several of these changes happen regardless of target modality except for the substitution of the relevant sensory region. In particular, in visual orienting, a lateralized increase in synchronization in the gamma band occurs transiently around 250-300 ms after cue onset, and an increase in alpha band synchronization begins around that time and continues until target onset. Moreover, local alpha-band synchronization increases in occipital cortex ipsilateral to the target location and decreases contralateral to it, indicating that local and long-distance synchronization play different, complementary, roles in this task. Finally, I will present preliminary evidence from auditory attention orienting that theta synchronization maintains orienting networks whereas gamma synchronization indexes communication within them, based on within- and across-frequency coupling analyses.
17:00 à 18:00
