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Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil ( dendrites and unmyelinated axons), glial cells ( astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distinguished from
white matter White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribu ...
in that it contains numerous cell bodies and relatively few myelinated axons, while white matter contains relatively few cell bodies and is composed chiefly of long-range myelinated axons. The colour difference arises mainly from the whiteness of
myelin Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can ...
. In living tissue, grey matter actually has a very light grey colour with yellowish or pinkish hues, which come from capillary blood vessels and neuronal cell bodies.


Structure

Grey matter refers to unmyelinated neurons and other cells of the central nervous system. It is present in the brain, brainstem and cerebellum, and present throughout the spinal cord. Grey matter is distributed at the surface of the cerebral hemispheres ( cerebral cortex) and of the cerebellum ( cerebellar cortex), as well as in the depths of the cerebrum (the thalamus; hypothalamus; subthalamus, basal gangliaputamen, globus pallidus and nucleus accumbens; as well as the
septal nuclei The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum. The septal nuclei are loc ...
), cerebellum (deep cerebellar nuclei – the dentate nuclei, globose nucleus, emboliform nucleus, and fastigial nucleus), and brainstem (the substantia nigra,
red nucleus The red nucleus or nucleus ruber is a structure in the rostral midbrain involved in motor coordination. The red nucleus is pale pink, which is believed to be due to the presence of iron in at least two different forms: hemoglobin and ferritin. ...
, olivary nuclei, and cranial nerve nuclei). Grey matter in the spinal cord is known as the grey column which travels down the spinal cord distributed in three grey columns that are presented in an "H" shape. The forward-facing column is the anterior grey column, the rear-facing one is the
posterior grey column The posterior grey column (posterior cornu, dorsal horn, spinal dorsal horn, posterior horn, sensory horn) of the spinal cord is one of the three grey columns of the spinal cord. It receives several types of sensory information from the body, inc ...
and the interlinking one is the lateral grey column. The grey matter on the left and right side is connected by the grey commissure. The grey matter in the spinal cord consists of interneurons, as well as the cell bodies of projection neurons. File:Cervical_vertebra_english.png, Cross-section of a spinal vertebra with the spinal cord in the centre (and grey matter labelled). File:Medulla spinalis - Section - English.svg, Cross-section of spinal cord with the grey matter labelled. Grey matter undergoes development and growth throughout childhood and adolescence. Recent studies using cross-sectional neuroimaging have shown that by around the age of 8 the volume of grey matter begins to decrease. However, the density of grey matter appears to increase as a child develops into early adulthood. Males tend to exhibit grey matter of increased volume but lower density than that of females.


Function

Grey matter contains most of the brain's neuronal cell bodies. The grey matter includes regions of the brain involved in muscle control, and sensory perception such as seeing and hearing, memory, emotions, speech, decision-making, and self-control. The grey matter in the spinal cord is split into three grey columns: * The anterior grey column contains motor neurons. These synapse with interneurons and the axons of cells that have travelled down the pyramidal tract. These cells are responsible for the movement of muscles. * The
posterior grey column The posterior grey column (posterior cornu, dorsal horn, spinal dorsal horn, posterior horn, sensory horn) of the spinal cord is one of the three grey columns of the spinal cord. It receives several types of sensory information from the body, inc ...
contains the points where sensory neurons synapse. These receive sensory information from the body, including
fine touch In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position ( proprioception), and pain. It ...
, proprioception, and
vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, su ...
. This information is sent from receptors of the skin, bones, and joints through sensory neurons whose cell bodies lie in the dorsal root ganglion. This information is then transmitted in axons up the spinal cord in spinal tracts, including the dorsal column-medial lemniscus tract and the spinothalamic tract. * The lateral grey column is the third column of the spinal cord. The grey matter of the spinal cord can be divided into different layers, called Rexed laminae. These describe, in general, the purpose of the cells within the grey matter of the spinal cord at a particular location. File:Anatomy and physiology of animals A reflex arc.jpg, Interneurons present in the grey matter of the spinal cord File:Medulla spinalis - Substantia grisea - English.svg, Rexed laminae groups the grey matter in the spinal cord according to its function.


Clinical significance

High alcohol consumption has been correlated with significant reductions in grey matter volume. Short-term cannabis use (30 days) is not correlated with changes in white or grey matter. However, several cross-sectional studies have shown that repeated long-term cannabis use is associated with smaller grey matter volumes in the hippocampus, amygdala, medial
temporal cortex The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe is involved in proc ...
, and prefrontal cortex, with increased grey matter volume in the cerebellum. Long-term cannabis use is also associated with alterations in white matter integrity in an age-dependent manner, with heavy cannabis use during adolescence and early adulthood associated with the greatest amount of change. Meditation has been shown to change grey matter structure. Habitual playing of action video games has been reported to promote a reduction of grey matter in the hippocampus while 3D platformer games have been reported to increase grey matter in the hippocampus. Women and men with equivalent IQ scores have differing proportions of grey to white matter in cortical brain regions associated with intelligence. Pregnancy renders substantial changes in brain structure, primarily reductions in grey matter volume in regions subserving social cognition. The grey matter reductions endured for at least 2 years post-pregnancy. The profile of brain changes is comparable to that taking place during adolescence, a hormonally similar transitional period of life.


History


Etymology

In the current editionFederative Committee on Anatomical Terminology (FCAT) (1998). ''Terminologia Anatomica''. Stuttgart: Thieme of the official Latin nomenclature, '' Terminologia Anatomica'', ''substantia grisea'' is used for English ''grey matter''. The adjective ''grisea'' for ''grey'' is however not attested in classical Latin. The adjective ''grisea'' is derived from the
French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...
word for grey, ''gris''. Alternative designations like ''substantia cana'' and ''substantia cinerea'' are being used alternatively. The adjective ''cana'', attested in classical Latin, can mean ''grey'', or ''greyish white''. The classical Latin ''cinerea'' means ''ash-coloured''.


Additional images

Image:Human brain right dissected lateral view description.JPG , Human brain right dissected lateral view Image:Gray678.png, Schematic representation of the chief ganglionic categories (I to V).


See also

* Grey matter heterotopia


References


External links

* {{DEFAULTSORT:Grey Matter Neuroanatomy Central nervous system