Cerebral cortical mechanisms of reaching movements.

Because reaching movements have a clear objective--to bring the hand to the spatial location of an object--they are well suited to study how the central nervous system plans a purposeful act from sensory input to motor output. Most models of movement planning propose a serial hierarchy of analytic steps. However, the central nervous system is organized into densely interconnected populations of neurons. This paradox between the apparent serial order of central nervous system function and its complex internal organization is strikingly demonstrated by recent behavioral, modeling, and neurophysiological studies of reaching movements.