Eye movement task measures inhibition and spatial working memory in adultswith schizophrenia, ADHD, and a normal comparison group

Schizophrenia and attention deficit/hyperactivity disorder (ADHD) are both associated with deficits in inhibition and working memory, although in ADHD the working memory deficit is hypothesized to be secondary to the inhibito ry deficit. This similarity in cognitive processes has been paralleled by s imilarities across the two groups in the performance of working memory and inhibition tasks. The delayed oculomotor response task is an alternative ta sk, which may allow greater separation of working memory from inhibitory co mponents, and thus its use may provide additional information on primary vs . secondary deficits in these disorders. Ten young adult ADHD sufferers, 10 schizophrenic subjects, and 10 normal subjects were matched on age, gender , and education. Eye movements were recorded during delayed oculomotor resp onse tasks with 1- and 3-s delays. Both the ADHD and the schizophrenic subj ects demonstrated dis-inhibition (an increased percentage of premature sacc ades); however only schizophrenic subjects demonstrated an impaired working memory (decreased spatial accuracy of the remembered saccade). The results are consistent with the hypothesis that working memory is a primary defici t in schizophrenia, but secondary to the inhibitory deficit in ADHD. (C) 20 00 Elsevier Science Ireland Ltd. All rights reserved.