General Control of Movement by the Cerebral Cortex
The control of movement by the central nervous system is a complicated process that involves multiple regions of the brain. While specific regions have been designated the “motor cortex,” almost all of the neocortex becomes engaged during the control of voluntary movement.
Consider some of the key components of a goal directed movement:
- An individual must first be aware of the surrounding environment and his position in space. This information is generated through somatosensory, proprioceptive, and visual sensory inputs to the posterior parietal cortex.
- The individual then decides what action is desired. This is accomplished via the parietal and anterior frontal lobes, which are extensively interconnected. These regions are thought to be important for abstract thought and decision making, and hence it is here that decisions about what actions to take are made and their likely outcomes are judged.
- A plan must then be constructed to determine how the actions will be carried out. This is performed in the premotor cortex (PMC) and supplemantary motor areas (SMA), where axons from the both the prefrontal and and parietal cortex converge. In this area the signals indicating what actions are desired are converted into signals that indicate how the actions will be perfomed.
- Finally, a command to begin the action must be issued and the plan must be implemented. This invloves the primary motor cortex, which, together with the PMC and SMA, contributes most of the axons to the descending corticospinal tract. From this region of the brain signals pass out to the muscles, converting the plan of action into an actual movement.
Source: Carlson, Neil Physiology of Behavior, 6th ed. Needham Heights, MA: Allyn and Bacon, 1998, pp.234-236, 242-245