Reduced Cortical Folding in Mental Retardation

BACKGROUND AND PURPOSE: MR is a developmental disorder associated with impaired cognitive functioning and deficits in adaptive behavior. With a 2D region of interest-based GI, a preliminary study reported significantly reduced gyrification in the prefrontal lobe in MR. The purpose of this study was to further investigate the abnormalities of cortical gyrification in MR and to explore the possible causes of these abnormalities. MATERIALS AND METHODS: Thirteen patients with MR and 26 demographically matched healthy controls were included in this study. A 3D surface-based IGI was calculated as a measure to quantify gyrification. Then vertex-by-vertex contrasts of IGI were performed between patients with MR and healthy controls. RESULTS: Statistical analysis showed that patients with MR had significantly reduced IGI in multiple brain regions compared with healthy controls. These regions include the lateral and medial prefrontal cortices, the right superior temporal gyrus, the left superior parietal lobe, the bilateral insular and adjacent cortices, and the visual and motor cortices. CONCLUSIONS: The observed abnormal pattern of cortical gyrification revealed by significant reduction of IGI in multiple brain regions might reflect the developmental disturbance in intracortical organization and cortical connectivities in MR.