Diffusion Tensor Imaging

The central nervous system (CNS) spans across different levels of organization, covering the gamut from genes to behavior. It is the aim of neuroscience to elucidate all these levels at a gross and an ultrastructural resolution and to define the relationships among them. One of the highest levels of organization is the systems level, which includes the motor, sensory, and central neural systems. Among the central systems are included those related to cognitive function, such as attention, memory, language, and executive function. Each system can be considered as a set of interconnected processors or centers constituted by nerve cells. Their physical connections are composed of axons of different lengths that can form fascicles as they run from origin to destination. Within the neocortex, these connections are selective and architectonic (1). How cytoarchitecture, connections, and function relate within the neocortex is a fundamental problem in neuroscience. This question addresses basic organizational principles of the nervous system and aims to elucidate the mechanisms through which the cerebrum mediates behavior (2,3). Behavior, to a large extent the product of cerebral function and at the same time a modulator of this function, is certainly the key to solving the problem of meaning related to any neural system. To explore thoroughly the behavioral dimension of an organism, it appears necessary to perform studies in vivo. If experi-