Neurophysiological evidence of corollary discharge dysfunction in schizophrenia

Objective: Speaking is hypothesized to generate a corollary discharge of mo tor speech commands transmitted to the auditory cortex, dampening its respo nse to self-generated speech sounds. Event-related potentials were used to test whether failures of corollary discharge during speech contribute to th e pathophysiology of schizophrenia. Method: The N1 component of the event-related potential elicited by vowels was recorded while the vowels were spoken by seven patients with schizophre nia and seven healthy comparison subjects and while the same vowels were pl ayed back. Results: In the healthy subjects, the N1 elicited by spoken vowels was smal ler than the N1 elicited by played-back vowels. This reduction in N1 elicit ed by spoken vowels was not observed in the patients with schizophrenia. Conclusions: These findings provide direct neurophysiological evidence for a corollary discharge that dampens sensory responses to self-generated, rel ative to externally presented, percepts in healthy comparison subjects and its failure in patients with schizophrenia.