Spatial organization of cortical and spinal neurons controlling motor behavior

A major task of the central nervous system (CNS) is to control behavioral actions, which necessitates a precise regulation of muscle activity. The final components of the circuitry controlling muscles are the motorneurons, which settle into pools in the ventral horn of the spinal cord in positions that mirror the musculature organization within the body. This 'musculotopic' motor-map then becomes the internal CNS reference for the neuronal circuits that control motor commands. This review describes recent progress in defining the neuroanatomical organization of the higher-order motor circuits in the cortex and spinal cord, and our current understanding of the integrative features that contribute to complex motor behaviors. We highlight emerging evidence that cortical and spinal motor command centers are loosely organized with respect to the musculotopic spatial-map, but these centers also incorporate organizational features that associate with the function of different muscle groups during commonly enacted behaviors.

► The neural control of complex movement is founded in the coordination of motor pool activity. ► Cortical and spinal neurons are spatially organized to reflect body space and behavioral function. ► Neural circuits for movement specify diverse motor parameters such as muscle, force, and endpoint. ► Spinal interneurons integrate multimodal inputs and relay commands to motor pools.