Characterization of motor cortex activity of the lower limb region.

Understanding the functional properties of the motor cortex is a key step to developing effective neuroprosthetic and computer interfaces for amputees and patients with spinal cord injury. Most efforts have been directed towards studying the upper limb region of the motor cortex. Little has been done in the way of addressing lower limb motor cortical physiology. In this study, we implanted multiple microelectrode arrays along the central sulcus in the primary motor cortex of a macaque monkey. Using intracortical microstimulation, we identified neurons that evoked leg movements, either exclusively or mostly, and we studied their firing activity during a center-out arm movement task. We found that some of these neurons modulated their firing rate during arm movement. Surprisingly, we found that some of these neurons even had selective tuning to the direction of arm movement. We built a decoding model which was able to predict the direction of arm movement based on putative leg motor cortical firing activity significantly better than chance. These findings have interesting and surprising implications for understanding motor cortical physiology.