Neuroimaging evidence suggests that human Brodmann area 5 (BA5) within the superior parietal lobule contributes to movement planning. However, a causal role for the contribution of BA5 to preparatory processes has yet to be reported. We used paired-pulse transcranial magnetic stimulation to investigate the influence of human BA5 on corticospinal excitability during movement preparation in the context of a GO/NO-GO task. Functional connectivity between BA5 and the ipsilateral primary motor cortex (M1) was investigated by probing corticospinal output to the first dorsal interosseous muscle of the right hand. Results indicate that BA5 influences M1 during movement preparation in a task-specific manner: motor-evoked potentials are suppressed in the context of a NO-GO versus GO task. These findings provide evidence that human BA5 participates in movement preparation and differentiates between whether a movement is withheld or executed.

Spinal cord injury may lead to complete or incomplete damage to ascending sensory and/or descending motor pathways and therefore alter neural circuits of the primary motor cortex. Transcranial magnetic stimulation (TMS) is a valuable tool for investigating the function of neural circuitry within primary motor cortex and also for promoting plasticity in these circuits for the ultimate purpose of improving the control of movement. For spinal cord injury, information about motor cortical circuits and TMS approaches to induce plasticity in these circuits is steadily emerging. In this review, we discuss TMS investigations of motor cortical circuitry and review TMS approaches to promote plasticity in motor cortical circuitry in spinal cord injury.