I. Introduction
The cortex of the human brain is a thin convoluted sheet comprised of gyri and sulci, which are folds oriented outwards and inwards, respectively. It is believed that many cortical sulci are linked to the underlying cytoarchitectonic and functional organization of the brain, although this relationship varies throughout the cortex and is not well understood at present. Recently, there has been great interest within the brain imaging community in developing image analysis methods for characterizing sulcal shapes. Such methods would have several applications. First, sulci are natural pathways to deeper brain structures in certain neurosurgical procedures. Therefore, having better understanding of their structure is important in neurosurgical planning [1]. Second, it has been suggested that sulcal shapes are related to the underlying connectivity of the brain, since they are influenced by forces exerted by connecting fibers [2]. Therefore, shape analysis of the sulci is important in understanding normal variability, as well as in studying developmental disorders or effects of aging.