Exploring the short term visual store in schizophrenia using the attentional blink.

Schizophrenia patients exhibit numerous deficits on visual processing tasks, ranging from very early stages of visual processing (e.g., backward masking) to the later working memory stages (e.g., delayed match-to-sample, N-back). However, little is known about deficits in an intermediate stage of visual information processing, namely short term visual memory (STVM). The attentional blink (AB) paradigm is considered to be a valid way to assess the STVM, and recent studies have reported AB deficits in schizophrenia. However, it is not clear whether the reported AB deficit in schizophrenia patients is due to their increased susceptibility to backward masking or increased vulnerability in the STVM. In this study we first found poorer performance in the AB task in 37 schizophrenia patients compared to 26 normal controls. To examine the effects of increasing and decreasing mask strength on AB performance in patients and controls, we next systematically varied the masking effect by varying the length of the distracters immediately following the targets. The manipulation had relatively little effect on the patient--control differences and patients continued to show an enhanced AB effect across conditions. The findings suggest that the enhanced AB effect in schizophrenia reflects an abnormality in their short term visual memory, as opposed to their enhanced susceptibility to visual masking.