Neurocognitive measures of prefrontal cortical dysfunction in schizophrenia

Frontal lobe dysfunction in individuals with schizophrenia has frequently been detected using both neuroimaging and neuropsychological testing. Results from previous studies vary in the findings of regional specificity vs. generalized frontal cortical dysfunction. We sought to examine potential regional differences in frontal cortical functioning among patients with schizophrenia vs. a comparison group using two different neurocognitive tasks: the Gambling Task (GT) and the Wisconsin Card Sorting Test (WCST). In general, the GT is thought to reflect function of the ventromedial prefrontal cortex (VMPFC), while the WCST reflects function of the dorsolateral prefrontal cortex (DLPFC). Twenty individuals with schizophrenia or schizoaffective disorder and 15 nonpsychiatrically ill comparison subjects underwent an assessment battery consisting of the GT, WCST, and positive and negative symptom ratings. Patients with schizophrenia performed worse on the GT with respect to total monetary gain (p=0.05) and total monetary loss (p<0.05). They also preferred disadvantaged vs. advantaged cards (p<0.04). Surprisingly, WCST performance was poor in both groups and was not significantly different between groups. These findings are at some variance with those in the previously reported literature, but nonetheless support the idea that prefrontal cortical areas mediating different cognitive tasks may be distinguished by specific neurocognitive assessments.