The effect of temporal predictability on sensory gating: Cortical responses inform perception.

Prepulse inhibition of perceived stimulus intensity (PPIPSI) is a phenomenon where a weak stimulus preceding a stronger one reduces the perceived intensity of the latter. Previous studies have shown that PPIPSI relies on attention and is sensitive to stimulus onset asynchrony (SOA). Longer SOAs may increase conscious awareness of the impact of gating mechanisms on perception by allowing more time for attention to be directed toward relevant processing channels. In other psychophysiological paradigms, temporal predictability improves attention to task relevant stimuli and processes. We hypothesized that temporal predictability may similarly facilitate attention being directed toward the pulse and its processing in PPIPSI. To examine this, we conducted a 2 (SOA: 90 ms, 150 ms) × 2 (predictability: low, high) experiment, where participants were tasked with comparing the perceived intensity of an acoustic pulse-alone against one preceded by a prepulse. The relationship between PPIPSI and cortical PPI (N1-P2 inhibition) was also investigated. Significant main effects of temporal predictability, SOA, and cortical PPI were revealed. Under high temporal predictability, both SOAs (90 and 150 ms) elicited greater PPIPSI. The findings indicate that temporal predictability enhances the timely allocation of finite attentional resources, increasing PPIPSI observations by facilitating perceptual access to the gated pulse signal. Moreover, the finding that reductions in N1-P2 magnitude by a prepulse are associated with increased probability of the participants perceiving the pulse "with prepulse" as less intense, suggests that under various experimental conditions, the link between these cortical processes and perception is similarly engaged.