Grey matter

Not to be confused with dark matter, a concept in theoretical physics.

Grey matter is a category of nervous tissue with many nerve cell bodies and few myelinated axons.

It forms the superficial parts of the brain and the deep parts of the spinal cord. It is composed of the bodies of the nerve cells (neuron) and the nonmyelniated sections of processes (axons and dendrites), including processes just emerging from the neurons. Grey matter is the major part of the nervous system in which the nerve impulses for all kinds of mental functions are produced and then sent away to be carried to their target organs by white matter.

The cerebral cortex and the basal ganglia, such as the putamen and the caudate nucleus, are composed of grey matter.

In general, grey matter can be understood as the parts of the brain responsible for information processing, whereas white matter is responsible for information transmission. In addition, grey matter - unlike white matter - does not have a myelin sheath and does not regenerate after injury.

Despite its name, grey matter may appear to have a pink hue, eventually losing its color after being removed from an active brain.