The purpose of this study is to investigate the effect of homotopic and heterotopic sensory afferent input on surround inhibition in the motor cortex. Surround inhibition is a cortical phenomenon, the function of which may be to suppress unwanted movements in surrounding muscles during voluntary actions. In support of this, a recent study showed that motor output to the little finger was reduced during self-paced, voluntary movements of the index finger, despite an increase in spinal excitability. Work has also shown that in relaxed muscle, homotopic and heterotopic peripheral stimulation results in time dependent modulation of motor cortical excitability. However, no studies have examined the relationship between volitional movement and afferent sensory input on cortical surround inhibition. Therefore, the aim of this study is to examine the changes in surround inhibition when electrical stimulation is applied to either the finger being actively moved (homotopic stimulation) or a separate finger not involved in the movement (heterotopic stimulation) at different time periods prior to the initiation of movements to assess the affect of these stimuli on surround inhibition and excitation in the motor cortex.