Reorganization of the Motor Cortex Following Spinal Cord Injury

Deafferentation of the spinal cord has been shown to produce extensive reorganization of the corresponding deafferented cortex. However, the role of the adjacent intact motor cortex and the integration between the primary motor (M1) and primary sensory cortex (S1) in this reorganization is not fully understood. In this study, we show that a contusion of the spinal cord increases the evoked responses of the forelimb, trunk, hindlimb, and tail motor cortices to forepaw stimuli in Layer II/III of anesthetized Sprague Dawley rats. Further, we show the identification of new evoked potentials to forelimb stimuli in motor regions below the level of the lesion. We also show a feasible stereotaxic solution for the simultaneous recording of evoked potentials from Layers I - V of M1 and S1. The increased responses in the forelimb motor cortex, coupled with the increased identification of evoked responses in the deafferented hindlimb and tail motor cortices, suggest that spatial reorganization of neuronal fibers within the motor cortex occurs through mechanisms involving the sprouting of either cortico-cortical connections from neighboring intact motor regions, or through sprouting of thalamocortical projections.