Neurological signs and the positive-negative dimension in schizophrenia

Schizophrenic patients have been observed to manifest a variety of abnormal neurological signs, but the nature of their association with differing clinical presentations is less well established. To address this issue, we administered a newly compiled neurological inventory to 28 well-characterized chronic schizophrenic inpatients and separately assessed them on the Positive and Negative Syndrome Scale and on control variables that included measures of global pathology, chronicity of illness, neuropsychological and intellectual integrity, and extrapyramidal dysfunction. We found, first, that our neurological battery provided statistically independent measures of apraxia, fine motor function, and prefrontal, parietal, and nonlocalizing signs. A significant association emerged between negative symptomatology and neurological signs of prefrontal impairment (p less than 0.01), which could not be accounted for by any of the control variables. Positive symptoms were associated with an absence of parietal and nonlocalizing signs; however, these correlations were mediated by higher neuroleptic doses in these patients. There was no association between any neurological sign and age, extrapyramidal symptoms, general neuropsychological integrity, education, IQ, or severity or chronicity of illness. We concluded that the negative syndrome in schizophrenia represents a distinct dimension of psychopathology that is related specifically to prefrontal deficit.