Two types of thought disorder and lateralized neuropsychological dysfunction

This report examined positive and negative thought disorder in relation to medication status and cerebral lateralization measures obtained from the Halstead-Reitan Neuropsychological Battery and Wechsler Adult Intelligence Scale in a sample of 59 patients with schizophrenia, schizoaffective and manic disorders, and unspecified functional psychoses. Discriminant function analyses of comparable left- and right-hemisphere variables from the neuropsychological tests were examined for both types of thought disorder, in which presence or absence of psychotropic medications was included as a variable in each analysis. Results indicated a relationship between positive thought disorder and left- but not right-hemisphere variables. Both the left- and right-hemisphere variables were related to negative thought disorder, and these relationships were influenced by the global measures of verbal and performance IQ as well as by medication status. These findings provide qualified support for the left-hemisphere-dysfunction hypothesis, insofar as it is associated specifically with positive thought disorder. Diffuse or bilateral cerebral impairment is more characteristic of negative thought disorder; however, medication status is also equivalent to neuropsychological variables in influencing this relationship.