Am J Psychiatry 1996; 153:1154-1157
Copyright © 1996 by American Psychiatric Association
Backward-masking deficit in adolescents with schizophrenic disorders or attention deficit hyperactivity disorder
BR Rund, M Oie and K Sundet
National Centre for Child and Adolescent Psychiatry, University of Oslo, Norway.
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.
