On the translation of directional motor cortical commands to activation of muscles via spinal interneuronal systems

I discuss in this paper some of the neural mechanisms by which directional motor cortical commands could be potentially translated into multi-muscle activations to generate a directed force (and initial movement) in space. Specifically, I review the results of recent studies in the motor cortex of monkeys and the spinal cord of the frog, and propose a possible mechanism by which these results could be formally connected. It is suggested that spinal mechanisms of the kind described in the spinal frog could serve as substrates for the operation of directionally tuned motor cortical activity to produce an appropriately directed motor output by the limb.