A tour of the brain: The Motor Cortex

How do we move? In the brain there is an area called the motor cortex which conducts the coordination of voluntary movements.

The principle site in the brain which governs our motor functions is the section highlighted in the above diagram, although the brain is such a complex organ that it is hard to pinpoint any exact locations. The control of voluntary movements is thought to be spread out across essentially the entire brain.

The location of  the Primary motor cortex was confirmed by the neurosurgeon Dr Wilder Penfield, who is notorious for the homunculus. This was a map of the functions within the cortex, with the ‘motor homunculus’ being a map of the motor cortex. The size of each body part of the model was proportional to the complexity of the movements that it can perform, meaning the hands and mouth were by far the largest. Somatotopy is the correspondence of an area of the body to a specific point in the central nervous system.

The blue area on the diagram above is known as the premotor Cortex. This section helps to guide our body movements, by preparing and executing limb movements. The supplementary motor area is involved in planning more complex movements and coordinating hand movements.

The Basal Ganglia

This is a group of structures within the brain which are involved in regulating the smoothness of movements. The caudate nucleus, the putamen, the globus pallidus and the subthalamic nucleus are all structures grouped under the basal ganglia.  There is an awful lot of neuroprocessing that occurs in the brain, with the basal ganglia playing a huge part for movements. There is a complex loop of processing in which data is sent to the basal ganglia, where it is processed and returned to the motor cortex via the thalamus. Once passing through the thalamus, the information is sent to the supplementary motor area.

http://webspace.ship.edu/cgboer/basalganglia.html – what happens when it goes wrong

The Cerebellum 

This is the croissant like structure at the base of the brain. The functions range from storing learned sequences of movements (probably an example is how my fingers know where each letter is positioned as I am typing), co-ordination, fine tuning movements to balance.

In order to compute these harmonious body movements, another information loop is involved, just as there is with the basal ganglia. First, information is sent to the cerebellum from the sensory and motor cortex, where it is processed and relayed back to the motor cortex. The force, direction and duration of movement are all properties of the information which the cerebellum adds to the message being sent back to the motor cortex.



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