Overlapping perceptual benefits of temporal attention in aperiodic and periodic streams are mediated by delta phase alignment, but not alpha suppression, in sensory circuits

Predictions about the timing of upcoming stimuli allow to allocate attention proactively, facilitating perceptual processing. While both periodic and aperiodic predictions were associated with anticipatory suppression of occipital alpha-band activity, periodic predictions are thought to uniquely affect perception through entrainment of delta-band activity directly at the level of the sensory cortex. Here we isolated the perceptual effects of interval-based aperiodic predictions using a challenging perceptual paradigm with a delayed response. We compared the perceptual facilitation to entrainment-based predictions in isochronous streams, and how they are mediated by distinct neural mechanisms in delta and alpha bands. Compared to an irregular non-predictive condition, both interval-based and periodic temporal predictions facilitated objective discrimination performance and subjective visibility reports to an equal degree. Neurally, interval-based predictions led to increased delta-band phase alignment, equally to that observed in isochronous streams, with both effects centered on occipital regions. A computational model of oscillatory entrainment revealed that these results cannot be explained by entrainment to the aperiodic stream. Interestingly, anticipatory alpha-band suppression did not differ between predictive and the non-predictive conditions, dissociating the perceptual effects of temporal attention from modulations of occipital alpha amplitude. Overall, these results indicate that top-down temporal predictions can shape visual processing through phase alignment of non-oscillatory low-frequency activity at the sensory cortex, pointing to the context-independent neural mechanisms of temporal attention at the cortical level. More broadly, they highlight the unique functional and neural features of temporal attention.