Dynamics of temporal attention and expectation revealed by continuous tracking of visual cortical responses

In processing a stream of visual information, visual perception is improved by temporal expectation, the timing predictability of sensory events, and by voluntary temporal attention, the prioritization of sensory events at behaviorally relevant time points. Although temporal expectation and attention are often treated as a single process, they can be dissociated and may be supported by distinct neural mechanisms. Here, we manipulated temporal attention while holding expectation constant and used concurrent MEG to disentangle their effects on visual cortical dynamics. Human observers attended to one of two sequentially presented visual targets embedded in flickering noise on each trial. Using the intertrial phase coherence (ITPC) of visually responsive channels as a measure of cortical response reliability, we found two neural signatures of temporal expectation and attention in visual cortical responses. First, a ramping increase in ITPC anticipated the temporally expected onset of visual targets whether attended or not, with the slope of the ramp modulated by temporal attention. Second, the transient evoked ITPC response to the first visual target was larger when that target was temporally attended. These data reveal distinct and complementary impacts of temporal attention and expectation on visual cortical responses across time.