Suppressed responses to self-triggered sounds in the human auditory cortex.

Humans are assumed to predict the sensory consequences of their own actions by means of forward models that enable discrimination between self-produced and external sensory signals. Here we tested whether responses in the human auditory cortex would differ to self-triggered versus externally triggered tones. The responses were recorded with a whole-scalp neuromagnetometer from 12 healthy subjects who either themselves triggered a tone by pressing a button once every 5 s or passively listened to externally triggered tones, presented in an identical sound sequence. Sources of the auditory N100m responses, peaking approximately 90 ms after sound onset in the supratemporal auditory cortex, were significantly weaker to self-triggered than to externally triggered sounds (suppressions 24 +/- 7% and 18 +/- 4% in the left and right hemispheres, respectively). These results support the existence of a forward model that predicts the auditory consequences of the subject's own motor acts on the environment--even with a tool--and thereby enables discrimination between self-produced and external sounds.