The neural mechanisms of audiotactile binding depend on asynchrony

Abstract

Asynchrony is a critical cue informing the brain whether sensory signals are caused by a common source and should be integrated or segregated. This psychophysics‐electroencephalography (EEG) study investigated the influence of asynchrony on how the brain binds audiotactile (AT) signals to enable faster responses in a redundant target paradigm. Human participants actively responded (psychophysics) or passively attended (EEG) to noise bursts, ‘taps‐to‐the‐face’, and their AT combinations at seven AT asynchronies: 0, ±20, ±70, and ±500ms. Behaviourally, observers were faster at detecting AT than unisensory stimuli within a temporal integration window: the redundant target effect was maximal for synchronous stimuli and declined within a ≤70ms AT asynchrony. EEG revealed a cascade of AT interactions that relied on different neural mechanisms depending on AT asynchrony. At small (≤20ms) asynchronies, AT interactions arose for evoked response potentials (ERPs) at 110ms and ~400ms post‐stimulus. Selectively at ±70ms asynchronies AT interactions were observed for the P200 ERP, theta‐band inter‐trial coherence (ITC) and power at ~200ms poststimulus. In conclusion, AT binding was mediated by distinct neural mechanisms depending on the asynchrony of the AT signals. Early AT interactions in ERPs and theta‐band ITC and power were critical for the behavioural response facilitation within a ≤±70ms temporal integration window