The effect of cognitive training on evoked potentials in schizophrenia

Electrophysiological indices are sensitive to cognitive dysfunction in schizophrenia but have rarely been used to assess benefits of cognitive remediation. Our aim was to evaluate the effect of specific cognitive training approaches on event-related potentials. Forty-six patients with schizophrenia underwent either auditory (AUD) or visuo-spatial (VIS) cognitive training or treatment-as-usual (TAU). Cognitive training was computer-assisted and administered for 10 sessions within two weeks. Event-related potentials during an active odd-ball paradigm together with clinical and neuropsychological variables were assessed before and after training and again at a two-month follow-up. Compared to the TAU group both the AUD and VIS training groups showed decreased P2 latency following training. At follow-up, the P2-latency reduction was stable in the VIS group but the AUD group experienced a relapse. Training resulted in improved digit-span backward among neuropsychological variables. Increased P2 amplitude was related to more positive symptoms and lower social-occupational functioning and longer P2 latency was associated with greater severity of stereotyped thinking. The more general visuo-spatial training appears to have a longer-lasting effect on P2 latency than the specific auditory training. Alternatively, there may be specific auditory discrimination deficits in schizophrenia requiring more extensive training for a stable change.