Reactions of human auditory cortex to a change in tone duration.

Auditory evoked magnetic fields were measured using a stimulation sequence where repetitive identical tone bursts were randomly and infrequently replaced by shorter tones. The deviation in the stimulus duration evoked a specific response, the mismatch field, peaking about 130 ms after the end of the shorter stimulus. The response can be explained by neural activity at the supratemporal auditory cortex. The results suggest the existence of a neural mechanism specific to changes in sound duration.