Visual backward masking deficits in schizotypy

Background: In visual backward masking, a target is followed by a mask impeding target perception. Visual backward masking is a potential endophenotype for schizophrenia because patients with schizophrenia and also their unaffected relatives show significant performance deficits compared to controls. If backward masking is an endophenotype, unaffected students with elevated schizotypal traits should also show relative backward masking impairments. In the past, research on endophenotypes has mostly focused on higher cognitive functions. For this reason, we also assessed performance in the widely used Wisconsin Card Sorting Test (WCST). Methods: We tested 40 healthy undergraduate students in the visual backward masking task and the WCST used in clinical studies before (Herzog et al., 2004; Chkonia et al., 2010). The visual backward masking paradigm is based on a two-step procedure. In the first step, we presented a visual target and determined the presentation time to reach 75% correct responses for each observer individually. With this step, we compensate for general, task-irrelevant effects. In the second step, this individual duration was used to assess the actual visual backward masking performance. Here, the target was followed by a masking stimulus (5 or 25 element grating) after a blank period (ISI). All participants filled in a self-report schizotypy measure, i.e. the O-life questionnaire assessing schizotypy along three dimensions, i.e. positive schizotypy (unusual experience), cognitive disorganization, and negative schizotypy (introvertive anhedonia). Results: We observed that both visual backward masking and the total number of errors in the WCST were impaired for students with high scores on the cognitive disorganization dimension. No significant differences were found for introvertive anhedonia scores or unusual experience scores. Discussion: The present findings indicate that both tasks are potential endophenotypes along the schizophrenia spectrum. However, previous studies indicate that the backward masking task is more reliable than higher cognitive tasks (e.g. WCST) (Herzog et al., 2004; Chkonia et al., 2010). Because our findings were specific to cognitive disorganization, we suggest that this dimension is the most illness-relevant schizotypy dimension. Our results show further evidence that visual backward masking is a potential endophenotype for schizophrenia.