Backward-masking deficit in adolescents with schizophrenic disorders or attention deficit hyperactivity disorder

OBJECTIVE: Backward masking is a cognitive task that involves the earliest phases of visual information processing. Disrupted task performance caused by a visual mask has been found repeatedly in schizophrenic patients; however, the specificity to schizophrenia of deficits in backward masking has received only limited study. METHOD: In this study 20 patients with early-onset schizophrenic disorders were compared to 20 adolescents with attention deficit hyperactivity disorder (ADHD) and 30 normal adolescents on a two-digit identification task in three backward-masking conditions: no mask, a short stimulus interval (33.0 msec), and a long stimulus interval (49.5 msec). RESULTS: The performance of the two groups of patients was similar, and both groups showed a statistically significant masking deficit after the long stimulus interval and a nearly significant deficit after the short stimulus interval in comparison with the normal subjects. CONCLUSIONS: Increased vulnerability to the masking stimulus was confirmed in schizophrenic subjects, but it is not specific to schizophrenia and is not accounted for by psychotic symptoms alone, since the subjects with ADHD performed similarly.