supplementary motor area

The supplementary motor area (SMA) is located on the medial surface of the cerebral hemisphere, in front of the primary motor strip. Stimulation of the SMA can cause vocalization or interrupt speech. It is also involved in large, often symmetrical, movements of both sides of the body. In experiments with monkeys, the SMA is active when an animal chooses to respond to one sensation over another, suggesting a role in decision-making related to movement. Fibers from the SMA project to the spinal cord, other brain areas, and the precentral gyri of both hemispheres. It is considered to be upstream from the primary motor area, initiating movements, while the primary motor area is involved in carrying them out. The SMA also receives input from the thalamus, which relays signals from the corpus striatum.12