EFFECTS OF P50 TEMPORAL VARIABILITY ON SENSORY GATING IN SCHIZOPHRENIA

The conditioning-testing (S1-S2) P50 auditory evoked potential (EP) ha s been well-documented and accepted as an important tool for measuring sensory gating in schizophrenia research. However, the physiological mechanism of the phenomenon is not known. In this study a single-trial analysis was used to determine the influence of the latency variabili ty of the responses in the formation of the averaged P50. Ten schizoph renic patients and 10 normal controls were tested in the dual-click EP paradigm. Using ensemble averaging analysis, we replicated the previo us finding of a lower S1 P50 amplitude and higher S2/S1 ratio in schiz ophrenics compared with normal controls. The single-trial analysis rev ealed that patients had significantly higher trial-to-trial latency va riability in S1 responses than normal subjects, while the S2 showed th e same variability as in controls. Measured by the single-trial proced ure, the arithmetic mean amplitudes of P50 responses to S1 and S2 were similar between normal and schizophrenic subjects. The same measure a lso eliminated the difference in averaged P50 amplitude between S1 and S2 for both groups. Temporal variability appears to be an important f actor in the assessment of averaged EPs and thus contribute to the cha nge of P50 amplitude observed in schizophrenia. (C) 1997 Elsevier Scie nce Ireland Ltd.