Brain Atlases of Normal and Diseased Populations

The concept of atlases in neuroscience is an old one (see Toga and Mazziotta, 1996 for a historical survey). Cartographic approaches have been used for centuries to identify and target specific regions in the brain and to establish relationships between a coordinate and a structure. In a brain atlas, spatial correspondence between a point in a coordinate system and a neuroanatomic feature was traditionally (and is sometimes still) achieved through definition of a set of rules governing pitch, roll, and yaw between a given brain and the atlas. Originally, the brain atlas was built around a rigid Cartesian coordinate system, but modern brain atlases incorporate flexible, computable systems that accommodate the sometimes considerable differences between a brain and the atlas. The transition from a static atlas representation to a computational one has resulted in dramatic extensions to the atlas concept. The brain atlas is now equivalent to a database: it incorporates a multitude of data points, all of which are organized, relational, extendable, and queriable. Originally, the brain atlas was purely neuroanatomical; now it can include functional information like descriptions of gene expression, receptor patterns, or connectivity. Originally, the brain atlas was built from a single, supposedly representative, example of the species at a single age (or weight); now it represents whole populations of individuals and statistically incorporates their distribution. Originally, the brain atlas was three dimensional (3D) (although most published book-form atlases were not accurate in the z axis). Now it incorporates time (making it four dimensional [4D]), from a scale of milliseconds (functional activity) to years (development and aging). Originally, the brain atlas depicted only the normal brain; now it can be used to describe a particular disease, and it may soon become a routinely applied biomarker for the detection of early stages in a pathological process or for assessing drug effects in clinical trials. This chapter reviews the background, evolution, and application of brain atlases in health and disease.