An electrophysiologic indication of auditory processing defects in autism.

Averaged evoked potentials (EPs) to clicks, random pitch changes (signals), and random deletions of stimuli within a regular train of tones were examined in five autistic and five normal children. Brainstem auditory EPs were abnormal in one of the autistic patients. The early cortical EP components P60 and N100 showed no differences across groups, whereas the P200 component of the cortical responses to clicks, as well as the late positive component (P300) to the pitch changes and deleted stimuli, were significantly smaller in the autistic subjects as a group. Furthermore, when P200 and P300 amplitudes were averaged across conditions for the individual subjects, these components were smaller in every autistic subject than in any of the normal subjects. These results are consistent with the view that there are auditory defects in autism that may sometimes involve lower levels of neural transmission as manifested by abnormalities in the brainstem and auditory EP, but are more consistently manifest in higher aspects of processing that involve the registration and storage of stimulus information. It is suggested that the severe language disorder in childhood autism may be secondary to the basic deficits in higher auditory processing.