Limbic hyperactivity associated to verbal memory deficit in schizophrenia

In schizophrenia there seems to be an inefficient activation of prefrontal and hippocampal regions. Patients tend to show worse cognitive performance in functions subserved by those regions as compared to healthy controls in spite of higher regional activation. However, the association between activation abnormalities and cognitive deficits remains without being understood. In the present study, we compared cerebral perfusion using single-photon emission tomography (SPECT) in patients and controls to study the association between activation patterns and cognitive performance in this disease. The SPECT studies were simultaneously obtained with an electrophysiological recording during a P300 paradigm to elicit P3a and P3b components. We included 23 stable patients with paranoid schizophrenia and 29 healthy controls that underwent clinical and cognitive assessments. Patients with schizophrenia showed an increased perfusion in the right hippocampus with respect to healthy controls, they also displayed a statistically significant inverse association between perfusion in the left hippocampus and verbal memory performance. Healthy controls showed an inverse association between perfusion in the left dorsolateral prefrontal (DLPFC) region and working memory performance. P3b but not P3a amplitude was significantly lower in patients. The limbic overactivation in the patients may contribute to their cognitive deficits in verbal memory.