| Human brains, and those of most higher mammals, are gyrencephalic (folded) to accommodate a large cortical surface within the limited volume of the skull. Abnormal folding of the cerebral cortex in humans is associated with a number of neurological dysfunctions and diseases such as schizophrenia and Williams syndrome. To understand the mechanism of gyrification, and to illuminate the underlying causes of abnormal folding, objective, quantitative methods to characterize normal and abnormal development must be developed. The ferret is an excellent model in which to study the development of convolutions in the brain because folding occurs post-natally over a period of several weeks, and the brain can be imaged conveniently in small-animal magnetic resonance (MR) scanners. Here, MR imaging was used to acquire three-dimensional image volumes of the ferret brain in vivo at different stages during the period of cortical folding. Through segmentation of these volumes, surface representations of the cortex are generated at each time point. A novel intra-subject registration algorithm (LAndmark Correspondence and Relaxation Of Surface Strain: LACROSS), which provides a point-to-point correspondence between two surfaces, is applied to the cortical surfaces from two ferret kits. The resulting calculations of growth show regional patterns within the cortex, and temporal variations over this period of early brain development. |
