Gyrification in first-episode schizophrenia: a morphometric study

Background A number of studies have found localized differences in the appearance and extent of cortical folding between the brains of schizophrenic patients and healthy control subjects. This study aimed to determine whether there are differences in gyral folding in schizophrenia by conducting a detailed analysis of magnetic resonance images. Methods Thirty-four young adults in their first episode of schizophrenia and 36 age-matched, healthy control subjects were studied. The gyrification index (GI), the ratio of the inner and outer cortical surface contours, was measured bilaterally on every second 1.88-mm image slice in four specifically defined lobar regions. Independent t tests were conducted for each region, followed by post hoc analysis of variance testing for the effects of laterality. Results Gyrification index values between groups corresponded closely in the occipital and parietal regions but were significantly increased in the right temporal lobe of the schizophrenic patients. Calculating the GI by two different methods (used in previous studies) notably affected results. Gyrification index values were significantly lateralized in the frontal and temporal regions, with no group × side interactions. Conclusions Differences in the temporal lobe GI of first-episode schizophrenic patients might reflect disturbed or abnormal connectivity. Further examination of specific sources of sulco–gyral difference in schizophrenia is required to clarify this.