Evidence of abnormalities in mid-latency auditory evoked responses (MLAER) in cognitive subtypes of patients with schizophrenia.

Abnormalities in measures of mid-latency auditory evoked responses (MLAER) have frequently been reported in schizophrenia, while few studies have examined whether these measures could distinguish cognitive subtypes of schizophrenia. The aim of this study was to investigate whether patterns of performance on MLAER measures could differentiate a cognitive subtype of patients characterized by pervasive cognitive deficits (CD) from patients with only mild cognitive deficits (CS) and controls. An auditory paired-click conditioning test was administered to 55 schizophrenia patients (26 CD, 29 CS) and 49 healthy controls. Amplitudes, latencies and sensory gating indices of the P50, N100, and P200 MLAER were analysed. The results showed that CD patients exhibited smaller S1 amplitudes of N100 and P200 than controls, while CS patients were comparable to controls. Binary logistic regression identified the P200 S1 amplitude as a significant predictor of patients' membership in the CD subtype. However, none of the other MLAER measures could differentiate the two subtypes of schizophrenia. These findings suggest that the abnormal pathophysiologic mechanisms underlying the electrophysiological brain responses to auditory stimulation are associated with the pervasive cognitive deficits, which characterize the CD subtype of schizophrenia. This finding might provide additional electrophysiological endophenotypes for future genetic research of schizophrenia.