Sulcal basins and sulcal strings as new concepts for describing the human cortical topography Gabriele Lohmann, D. Yves von Cramon Max-Planck-Institute of Cognitive Neuroscience Inselstraße 22-26, 04103 Leipzig, Germany lohmann,cramon @cns.mpg.de Abstract Human brain mapping aims at establishing correspon- dences between brain function and brain anatomy. One of the most intriguing problems in this field is the high inter-personal variability of human neuroanatomy which makes studies across many subjects very difficult. The cortical folds (“sulci”) often serve as landmarks that help to establish correspondences between subjects. In this paper, we will present a method that both au- tomatically detects and attributes neuroanatomical names to the cortical folds using image analysis methods applied to magnetic resonance data of human brains. We claim that the cortical folds can be subdivided into a number of substructures which we call sulcal basins. In addition to the concept of sulcal basins, we introduce the concept of sulcal strings which are groups of sulcal basins arranged as strings that are aligned with the Sylvian fissure and the inter-hemispheric cleft. The concept of sulcal basins allows to establish a com- plete parcellation of the cortical surface into separate re- gions. These regions are neuroanatomically meaningful and can be identified from MR data sets across many sub- jects. At the same time, the parcellation is detailed enough to be useful for brain mapping purposes. 1 Introduction The folding of the cortical surface of the human brain varies dramatically from person to person. However, the folding pattern is not completely arbitrary. In fact, the cortical folds (also called “sulci”) often serve as land- marks for referencing brain locations, and the more pro- nounced sulci have names that are well established in the neuroanatomical literature [1]. In this paper, we will present a new method that both automatically detects and attributes neuroanatomical names to these folds. More precisely, we subdivide each fold into a number of substructures which we call sulcal basins, and attach labels to these substructures. The rea- son why we introduce the concept of a sulcal basin is that we believe that sulcal basins have a lower degree of inter- personal variability than entire sulci. The work we present here is an extension of our earlier work([2]) which differs in that we introduce a new type of spatial relationship to characterize sulcal basins which lead to a significant increase in classification accuracy. In particular, we exploit the fact that sulcal basins are ar- ranged in three distinctive strings across the cortical sur- face. The first string is aligned with the inter-hemispheric cleft, the second string is aligned with the Sylvian fis- sure and a third string is located in between the first two strings. We will present a method of locating these three strings, and putting them to use as spatial constraints in the identification process. Our method is important in the context of human brain mapping. Human brain mapping aims at establishing cor- respondences between brain function and brain anatomy. One of the most intriguing problems in this field is the high inter-personal variability of human neuroanatomy which makes studies across many subjects very difficult. Most previous attempts at solving this problem are based on various methods of image registration where