Insular cortex abnormalities in schizophrenia: Relationship to symptoms and typical neuroleptic exposure

The insular cortex is a limbic integration region engaged in emotional and cognitive functions. Previously, we found that neuroleptic-naive subjects had abnormally small insular volumes compared with control subjects, with volume directly related to severity of psychotic symptoms.

To further investigate insular cortex abnormalities and their functional correlates, we measured insular gray matter volume and cortical surface size, using magnetic resonance images among 30 patients with schizophrenia and a matched control group. The sample was designed to represent a variety of phenomenologic profiles to provide sufficient variance in multiple measures, including severity of illness and exposure to neuroleptics (typical only).

There were no significant differences in morphology between patients and control subjects; however, among patients, psychotic symptoms were inversely correlated with insular volume, replicating our previous finding in neuroleptic-naive subjects. Neuroleptic exposure had a specific effect on insular morphology: increasing drug exposure (measured in dose-years) correlated with larger insular volume.

This effect of neuroleptic exposure might account for the lack of difference in structural measures in this more chronic sample, whereas the initial study on neuroleptic-naive subjects showed group differences. Further research is needed to investigate the potential relationship between changes in insula volume from neuroleptic exposure and clinical outcome.