Midlatency auditory evoked responses in schizophrenia.

The auditory evoked component P50 has been reported as having an abnormal recovery cycle in patients with schizophrenia. Recent studies examining the effects of stimulus rate on the midlatency response (MLR) component P1, found P1 recovery cycles in normals similar to P50. This study examined the P1 recovery cycle in patients using a rate protocol and MLR recording procedures. MLRs were recorded from 13 controls and 13 patients with schizophrenia in response to binaurally presented clicks presented at three stimulus rates: 0.9/sec, 5.1/sec, and 9.9/sec. The P1 (50-70 msec latency) in patients did not decrease as much in amplitude as in controls at the 9.9/sec stimulus rate. This lack of recovery was correlated with clinical ratings of symptomatology. Since evidence from both the human and the cat model suggests that the P1 is generated in thalamus, these findings are consistent with reports of thalamic dysfunction in schizophrenia.