Suppression of the auditory N1 event-related potential component with unpredictable self-initiated tones: evidence for internal forward models with dynamic stimulation.

Internally operating forward model mechanisms enable the organism to discriminate the sensory consequences of one's own actions from other sensory events. The present event-related potential (ERP) study compared the processing of self-initiated tones with the processing of externally-initiated but otherwise identical tones. In different conditions, frequency and onset of the sound were either predictable or unpredictable. The amplitudes of the N1 component of the ERP for the self-initiated relative to the ones for externally-initiated sounds were significantly attenuated even when the particular frequency or sound onset could not be predicted by the subject. These results support internal forward model mechanisms which dynamically predict the sensorial consequences of ones own motor acts even in face of uncertainties with respect to the frequency of the sound and its onset. Moreover, the attenuation effect was reduced when the frequency was unpredictable suggesting that it is easier to discriminate a self-initiated sound with exact foreknowledge.