Sensory attenuation of self-initiated sounds maps onto habitual associations between motor action and sound
Sensory attenuation refers to reduced brain responses to self-initiated sensations relative to those produced by the external world, a distinction that is vital for dynamic motor control and our sense of agency. Typically, willed vocalizations elicit larger N1 reduction of the auditory evoked potential compared to indirectly evoked sounds, such as tones generated by button-presses, which is attributed to the prediction and cancellation of incoming signals enabled by speech motor commands. However, physical confounds exist, including different stimuli and the increased motor artefact associated with mouth vs. finger movements. The present study investigated N1 attenuation to physically identical sounds evoked by hand, eye, and mouth-initiated movements. Twenty-eight healthy participants had their electroencephalogram (EEG) recorded as they blew into a microphone, pressed a button, or moved their eye to generate a pure tone. We found that N1 and P2 response was most reduced in the blow initiation condition, and that both blow and button-press but not saccade initiated tones elicited significantly reduced N1 and P2 amplitude compared to external initiation. This indicates that the eliciting motor action markedly influences ERP response to auditory stimuli. Given that saccades are never associated with sounds, finger movements sometimes are, and mouth movements often are, the pattern of results suggests that N1 attenuation to self-initiated sounds may depend on existing associations between the initiating action and resultant sensation.