High-frequency, long-range coupling between prefrontal and visual cortex during sustained attention

Electrical recording studies in humans and monkeys have shown attentional enhancement of evoked responses and gamma synchrony in ventral stream cortical areas, but it is unknown if synchrony results from intrinsic activity in visual cortex or from inputs from other structures. Based on paired-recordings in the frontal eye field and area V4, we find that attention to a stimulus in their joint receptive field leads to enhanced oscillatory coupling between the two areas, which is particularly strong at gamma frequencies. Our data suggest that this coupling between areas is initiated by the frontal eye field and is time-shifted by about 8-13 ms across a wide range of frequencies. Taking into account the expected conduction and synaptic delays between the two areas, this time-shifted coupling at gamma frequencies may optimize the postsynaptic impact of spikes from one area upon the other, improving cross-area communication with attention and potentially other cognitive states.