Distinct neural mechanisms and temporal constraints govern a cascade of audiotactile interactions

Abstract

Asynchrony is a critical cue informing the brain whether sensory signals are caused by a common source and should be integrated or segregated. It is unclear how the brain binds audiotactile signals into behavioural benefits depending on their asynchrony. Participants actively responded (psychophysics) or passively attended (electroencephalogrpahy) to noise bursts, taps-to-the-face, and their audiotactile (AT) combinations at seven audiotactile asynchronies: 0, {+/-}20, {+/-}70, and {+/-}500ms. Observers were faster at detecting AT than unisensory stimuli, maximally for synchronous stimulation and declining within a [≤]70ms temporal integration window. We observed AT interactions for (1) near-synchronous stimuli within a [≤]20ms temporal integration window for evoked response potentials (ERPs) at 110ms and [~]400ms, (2) specifically {+/-}70ms asynchronies, across the P200 ERP and theta-band inter-trial coherence (ITC) and power at [~]200ms, with a frontocentral topography, and (3) beta-band power across several asynchronies. Our results suggest that early AT interactions for ERP and theta-band ITC and power mediate behavioural response facilitation within a [≤]70ms temporal integration window, but beta-band power reflects AT interactions that are less relevant for behaviour. This diversity of temporal profiles and constraints demonstrates how audiotactile integration unfolds in a cascade of interactions to generate behavioural benefits.