Attenuated human auditory middle latency response and evoked 40-Hz response to self-initiated sounds.

For several modalities, it has been shown that the processing of sensory information generated by our own actions is attenuated relative to the processing of sensory information of externally generated stimuli. It has been proposed that the underlying mechanism builds predictions about the forthcoming sensory input and forwards them to the respective sensory processing levels. The present study investigated whether early auditory processing is suppressed by the top-down influences of such an internal forward model mechanism. To this end, we compared auditory middle latency responses (MLRs) and evoked 40-Hz responses elicited by self-initiated sounds with those elicited by externally initiated but otherwise identical sounds. In the self-initiated condition, the amplitudes of the Pa (27-33 ms relative to sound onset) and Nb (40-46 ms) components of the MLRs were significantly attenuated when compared to the responses elicited by click sounds presented in the externally initiated condition. Similarly, the evoked activity in the 40-Hz and adjacent frequency bands was attenuated. Considering that previous research revealed subcortical and auditory cortex contributions to MLRs and 40-Hz responses, our results support the existence of auditory suppression effects with self-initiated sounds on temporally and structurally early auditory processing levels. This attenuation in the processing of self-initiated sounds most probably contributes to the optimal processing of concurrent external acoustic events.