Neurobiological Correlates of Learning Potential in Healthy Subjects and in Schizophrenic Patients

Abstract

Dynamic testing has increasingly been recognized as a measure of neurocognitive modifiability. For instance, executive function deficits as measured by the Wisconsin Card Sorting Test (WCST) can be ameliorated in a subgroup of schizophrenic patients by integrating instructions and feedback into the testing procedure. In the first study reported herein, we investigated the relation between learning typology on the WCST and chronicity in 60 first-episode patients and 44 patients with chronic schizophrenia. We found that nonretainer categorization of WCST performance is not related to chronic schizophrenia. In the second study, we investigated the relationship between learning potential on the WCST and cerebral metabolism, assessed by single-voxel proton magnetic resonance spectroscopy of the dorsolateral prefrontal cortex (DLPFC) and the anterior cingulate cortex (ACC), in 43 schizophrenic patients and 37 matched healthy control subjects. The level of N-acetylaspartate (NAA), a marker of neuronal integrity, in the DLPFC correlated with performance on the dynamic WCST in healthy subjects. In schizophrenic patients, a significant correlation was observed between NAA in the ACC and learning potential (cf. Ohrmann et al., 2008). These data suggest the involvement of different neuronal networks in learning among schizophrenic patients as compared to healthy controls.