Progressive reduction of visual P300 amplitude in patients with first-episode schizophrenia: an ERP study

To understand the underlying dynamic neurophysiological changes over the course of schizophrenia, it is important to study subjects longitudinally from the early stage of the illness. We previously reported that visual P300 was already impaired in patients with first-episode schizophrenia (FESZ). This study demonstrates how the visual P300, as well as earlier components P1, N1, and N200, changed at the 1-year follow-up after their initial measurement.

Visual ERPs were recorded with the same experimental paradigm and acquisition protocol at both time points in FESZ (n = 18) and healthy comparison subjects (n = 24). Participants silently counted infrequent target stimuli ("x") amid standard stimuli ("y") presented on the screen while the 64-channel electroencephalogram was recorded.

FESZ showed smaller visual P300, N200, P1 (trend level) amplitude and delayed P300 and N1 latency at both time points; however, only P300 showed progressive amplitude reduction over the course of the illness at 1-year follow-up. P300 latency did not change over time in either group. FESZ showed significantly reduced Spatial Span total score at both time points, and there was a significant negative correlation between P300 peak amplitude and the Brief Psychiatric Rating Scale positive symptom score at baseline.

These data show progressive P300 amplitude reduction in response to visual stimuli in the early stage of schizophrenia. These visual P300 findings support the concept of progression of schizophrenia, suggesting the usefulness of the visual P300 as a biological marker of progression.