Top-Down Attention Modulates Phase Effects on Audio-Tactile Processing

Multisensory processing is necessary in our daily lives, which is modulated by the temporal alignment of multiple sensory inputs. However, it remains poorly understood if and how selective attention interacts with this temporal alignment to further modulate audio-tactile processing. This study aimed to explore how selective attention and temporal alignment influence cortical responses to rhythmic audio-tactile streams. Participants were exposed to periodic auditory tones embedded in continuous background noise, either presented alone or paired with fluctuating tactile stimulation that was either in-phase or anti-phase with the tones. Selective attention was manipulated by instructing participants to perform an auditory detection task focusing on either the tones or the background noise. Electroencephalography recordings revealed that anti-phase audio-tactile inputs, compared to auditory-only inputs, elicited enhanced cortical steady-state responses and phase-locking to the tones. Importantly, this effect was further enhanced when participants paid attention to the tone, potentially reflecting the resolution of sensory competition among the simultaneous auditory and tactile inputs. In-phase tactile inputs elicited nonsignificant increases in tone processing regardless of attention. In sum, these findings underscore the dynamic interplay between bottom-up temporal alignment and top-down attentional modulations in audio-tactile processing, providing insights into how the brain integrates audio-tactile information.