Neurophysiological sensitivity to attentional overload in patients with psychotic disorders

Objective: Disturbances of information selection under high processing load might be a key feature predisposing to psychotic disorders. The N2pc component of the ERP is a specific measure of selective attention. It is unclear whether N2pc is altered under increased demands in patients with psychosis. Methods: Patients with schizophrenia, with bipolar disorder (n= 20 each), and age-matched healthy controls (n= 21) had to identify two targets (" T1" and "T2") in two different simultaneous rapidly presented series of letters. We assessed the target-evoked N2pc and P3 components and the visually evoked potentials (VEPs) evoked by the rapid stream. Results: T1 and T2 identification rates did not substantially differ between groups. However, T1- and T2-evoked N2pc components were reduced in both patient groups. VEPs were enlarged in response to the first stimulus of the fast series in healthy participants but not in patients. T2-evoked P3 was reduced in patients with schizophrenia only. Conclusions: Under high attentional load, neurophysiological mechanisms underlying visual selection are compromised in patients with psychosis. The lacking VEP increase to the first stimulus probably indicates deficient arousal. Significance: These deficiencies of attentional selection and arousal might enhance liability to psychotic symptoms under stressful conditions.