RELATIONS BETWEEN NEUROPSYCHOLOGICAL PERFORMANCE AND BRAIN MORPHOLOGICAL AND PHYSIOLOGICAL MEASURES IN MONOZYGOTIC TWINS DISCORDANT FOR SCHIZOPHRENIA

Correlational approaches that examine the relation between neuropsycho logical measures and brain morphology or physiology in schizophrenia h ave yielded inconsistent results. This may be due in part to difficult ies in ascertaining precisely to what degree each measure deviates fro m its genetically and enviromentally determined potential level. We at tempted to surmount this problem in a paradigm involving monozygotic t win pairs discordant for schizophrenia. In this paradigm, the differen ce score between the unaffected member and affected member of a twin p air should represent the degree of pathologic involvement irrespective of actual level. In correlating intrapair difference scores of anatom ic structures measured from magnetic resonance imaging (n = 15) and pr efrontal regional cerebral blood flow (rCBF) (n = 10) with cognitive a bilities (after partialing IQ), we found strong associations between ( 1) the left hippocampus and a parameter of verbal memory, and (2) pref rontal rCBF with symptom scores and perseveration on the Wisconsin Car d Sorting Test. These results support other research implicating media l temporal and prefrontal regions as important in the symptomatic expr ession and cognitive failures of schizophrenia. Overall, however, ther e was a relative paucity of significant associations between neuroanat omic and neurocognitive variables. This may have been due to the relat ively restricted ranges of hippocampal size or cognitive ability found in this sample.