Neurophysiological sensitivity to attentional overload in patients with psychotic disorders

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.

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.

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.

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.

These deficiencies of attentional selection and arousal might enhance liability to psychotic symptoms under stressful conditions.