Independent frontal-system deficits in schizophrenia: cognitive, clinical,and adaptive implications

This study examined whether frontal-system impairments in schizophrenia occ ur independently of one another and whether they have distinct implications for information processing, symptom severity, and adaptive functioning. We assessed 26 medication-free schizophrenic outpatients and 18 normal contro l subjects on eight frontally mediated tasks, semantic information processi ng, IQ, the BPRS, and long-term psychosocial adaptation. Schizophrenic subj ects showed three types of deficits, which were uncorrelated with one anoth er: (1) Executive dysfunction (inflexible problem solving) was related to d ecreased use of expectancy during controlled semantic priming, lower intell igence, more severe negative symptoms and stereotyped mannerisms. (2) Disin hibition of responses (to irrelevant stimuli) was associated with increased automatic priming, a trend for more severe hallucinations, and was unrelat ed to intelligence. (3) Motor dyscoordination (inaccurate, dysfluent motor sequencing) was not related to semantic processing, intelligence, or sympto ms. Furthermore, all three impairments were unrelated to generalized slowne ss, age, sex, illness length, or pre-washout neuroleptic dose. Two deficits accounted for aspects of long-term psychosocial adaptation, even after sta tistical correction for IQ: Executive dysfunction was associated with young er illness onset, poor purposefulness and planning, impaired social relatio ns, and lower global functioning. Motor dyscoordination was associated with poor treatment outcome and restricted educational advancement. Furthermore , executive and motor deficits interacted significantly; subjects who had b oth deficits showed the least favorable treatment outcome. These findings a re neither consistent with generalized impairment nor with a unitary 'front al syndrome' in schizophrenia. They provide preliminary evidence for at lea st three frontal-system deficits (dorsolateral, orbital, and premotor), whi ch are dissociable from one another, can occur without general intellectual impairment, and have distinct implications for long-term adaptive function ing. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.