Cortical abnormality in schizophrenia: an in vivo application of the gyrification index.

To investigate the hypothesis that patients with schizophrenia exhibit gross cortical abnormalities of developmental origin, we utilized the gyrification index (GI) (ratio of inner to outer cortical contours), a measure of overall cortical folding, in an in vivo magnetic resonance imaging study of young, strongly right-handed male patients and controls. The two groups did not differ with respect to whole-brain volume, age, or handedness. In an examination confined to the left hemisphere, mean GI values were significantly reduced in the patient group in both anterior and posterior regions. Neither age nor length of illness were found to be significant predictors of GI variance in the patients group, suggesting that GI reductions do not result from an ongoing atrophic process. Rather, these results are consistent with the hypothesis of neurodevelopmental abnormalities in schizophrenia that result in an overall reduction in cortical folding.