Relatively few magnetic resonance imaging studies of schizophrenia have investigated the entire cerebral cortex. Most focus on only a few areas within a lobe or an entire lobe. To assess expected regional alterations in cortical volumes, we used a new method to segment the entire neocortex into 48 topographically defined brain regions. We hypothesized, based on previous empirical and theoretical work, that dorsolateral prefrontal and paralimbic cortices would be significantly volumetrically reduced in patients with schizophrenia compared with normal controls.
Twenty-nine patients with DSM-III-R schizophrenia were systematically sampled from 3 public outpatient service networks in the Boston, Mass, area. Healthy subjects, recruited from catchment areas from which the patients were drawn, were screened for psychopathologic disorders and proportionately matched to patients by age, sex, ethnicity, parental socioeconomic status, reading ability, and handedness. Analyses of covariance of the volumes of brain regions, adjusted for age- and sex-corrected head size, were used to compare patients and controls.
The greatest volumetric reductions and largest effect sizes were in the middle frontal gyrus and paralimbic brain regions, such as the frontomedial and fronto-orbital cortices, anterior cingulate and paracingulate gyri, and the insula. In addition, the supramarginal gyrus, which is densely connected to prefrontal and cingulate cortices, was also significantly reduced in patients. Patients also had subtle volumetric increases in other cortical areas with strong reciprocal connections to the paralimbic areas that were volumetrically reduced.
Findings using our methods have implications for understanding brain abnormalities in schizophrenia and suggest the importance of the paralimbic areas and their connections with prefrontal brain regions.