parts or fields based on cytoarchitectonics, two dorsal fields and two ventral fields. They then studied the properties of the ventral premotor fields, establishing tactile, visual, and motor properties of a complex nature (summarized in greater detail above in Divisions of the premotor cortex). At least three representations of the hand were reported in the motor cortex, one in the primary motor cortex, one in the ventral premotor cortex, and one in the dorsal premotor cortex. By implication, at least three different cortical fields may exist, each one performing its own special function in relation to the fingers and wrist. For these and other reasons, a consensus has now emerged that the lateral motor cortex does not consist of a single, simple map of the body, but instead contains multiple subregions including the primary motor cortex and several premotor fields. These premotor fields have diverse properties. Some project to the spinal cord and may play a direct role in movement control, whereas others do not. Whether these cortical areas are arranged in a hierarchy or share some other more complex relationship is still debated. Graziano and colleagues suggested an alternative principle of organization for the primary motor cortex and the caudal part of the premotor cortex, all regions that project directly to the spinal cord and that were included in the Penfield and Woolsey definition of M1. In this alternative proposal, the motor cortex is organized as a map of the natural behavioral repertoire. The complicated, multifaceted nature of the behavioral repertoire results in a complicated, heterogeneous map in cortex, in which different parts of the movement repertoire are emphasized in different cortical subregions. More complex movements such as reaching or climbing require more coordination among body parts, the processing of more complex control variables, the monitoring of objects in the space near the body, and planning several seconds into the future. Other parts of the movement repertoire, such as manipulating an object with the fingers once the object has been acquired, or manipulating an object in the mouth, involve less planning, less computation of spatial trajectory, and more control of individual joint rotations and muscle forces. In this view the more complex movements, especially multi-segmental movements, come to be emphasized in the more anterior part of the motor map because that cortex emphasizes the musculature of the back and neck which serves as the coordinating link between body parts.