BACKWARD-MASKING PERFORMANCE IN UNAFFECTED SIBLINGS OF SCHIZOPHRENIC-PATIENTS - EVIDENCE FOR A VULNERABILITY INDICATOR

Background: Visual masking is a procedure that is used to assess the e arliest components of visual processing. In backward masking, the iden tification of an initial stimulus (the target) is disrupted by a later stimulus (the mask). The masking function can be divided into an earl y component (eg, up to about 60 ms) that reflects the involvement of s ensory-perceptual processes, and a later component that reflects susce ptibility to attentional disengagement as the mask diverts processing away from the representation of the target. Schizophrenic patients sho w anomalies on both masking components. It is not known whether backwa rd masking deficits reflect enduring genetic vulnerability to schizoph renia. Methods: We assessed 32 unaffected siblings of schizophrenic pa tients and 52 normal control subjects on the early and late components of 4 masking conditions. The conditions differentially involved the s ustained and transient visual pathways. Results: The unaffected siblin gs showed poorer overall performance than control subjects on the mask ing procedures. More specifically, siblings showed anomalies on the ea rly, sensory-perceptual component, but not on the later, attentional d isengagement component. Conclusions: The backward masking performance deficits that have been observed in schizophrenic patients appear to r eflect enduring vulnerability to the disorder rather than only the sym ptoms of the illness. This vulnerability appears to be associated with early, sensory-perceptual processes.