An electrophysiological investigation of attentional blink in schizophrenia: separating perceptual and attentional processes.

When two visual targets are presented in a rapid serial visual presentation (RSVP) paradigm, the ability to identify the second target is reduced when it is presented 200-500ms after the initial target. This phenomenon is referred to as the "attentional blink (AB)." Previous behavioral studies have reported aberrant AB in schizophrenia. The underlying cause, however, of the AB deficit in schizophrenia remains ambiguous. Individuals with schizophrenia consistently demonstrate impairments in early visual processing stages and later attentionally-mediated stages, yet the stage of processing that is contributing to patient-control differences on AB is unknown. The current study attempted to resolve this ambiguity by applying electrophysiological methodology to an RSVP paradigm with 70 clinically stable outpatients with schizophrenia and 63 healthy controls. The task was simplified to reduce task demands, and a suppression ratio was employed to control for possible differences between groups in the ability to identify a single stimulus within a visual stream. Early perceptual processing was assessed using the steady-state visual evoked potential (ssVEP), and attentional processing was assessed using the P300 event-related potential. Relative to the healthy controls, patients showed the expected behavioral AB deficits. These deficits coincided with reduced P300 amplitude: both performance and P300 reductions extended beyond the traditional AB window. Mean ssVEP amplitude did not differ between the groups, and the differences in P300 remained after controlling for ssVEP. These results suggest that the observed AB deficits were due to attentional, not perceptual, processing deficits.