White matter of the brain: structure and functions

The opposite side of the gray matter plays a very important role in the functioning of the brain.

The human brain is a complex structure. If we look at it from the outside we see a gelatinous mass of a roughly grayish color, with numerous protrusionsThe brain is a gelatinous mass, with numerous protrusions, grooves and convolutions lining its surface. Inside, however, a series of structures of a whitish color can be observed.

This change in coloration is not accidental: the neurons that make up the brain have different parts with different functions, having delimited the existence of two types of matter or substances throughout the nervous system: the gray matter, in which we find mainly somas or nuclei of neurons, and the white substance, also called white matter.

The white matter

The white matter is that part of the nervous system mainly made up of neuron axons, i.e., the part of the neurons responsible for transmitting the information processed by the soma to the rest of the system. Although the gray matter (also called gray matter) is especially visible in the cerebral cortex and inside the spinal cord, white matter can be found more easily in the inner structures of the brain and in the outermost part of the spinal cord..

The whitish coloration of this substance is due to the presence of myelin, a substance that coats the axons of most neurons. The main function of this myelin is to accelerate the transmission of information.. This acceleration is due to the fact that, thanks to the myelin, the information does not have to pass in a straight and continuous way through the axon, but through small jumps between the myelin sheaths (this type of communication is called jumping transmission).

Basic functions

The main function of the white matter is the correct transmission of brain information.. This substance has a great implication in allowing the human being to transfer the electrochemical pulses emitted by the brain to the rest of the body. In this way we can consider that it coordinates the communication between the different systems of the human body, both inside and outside the brain. Thanks to it, distant parts of the nervous system can maintain the necessary contact to work together.

That is why where there is white matter, the axons of neurons predominate, which means that these white areas of the brain are, in essence, neuronal highways. these white areas of the brain are, in essence, neuronal highways, communication zones between parts of the brain.communication zones between parts of the brain.

Other recently discovered functions

Traditionally, it has been assumed that what we have seen is the main function of the white matter, which was believed to be a passive element that was limited to transferring orders from the nucleus of the neuron to other cells. However, more recent research indicates that the white matter, apart from the mere transmission of information, is related to different cognitive elements, is related to different cognitive and emotional elements of the brain..

This is because the connection and speed offered by the substance allows the construction of neural networks that can govern different processes. Specifically, it greatly affects memory and learning, as well as the management of cognitive resources and executive functions. Thus, it has been indicated that the white matter greatly affects the development and use of intelligence..

Structure and internal configuration

As we have indicated, the white matter is predominantly made up of myelinated axons, which are the part of the neuron responsible for projecting the nerve impulse to relatively distant areas, with maximum speed and efficiency. This does not mean that somas, or even unmyelinated axons, cannot be found, but their proportion is much lower than in the gray matter, thus producing the visual effect that white predominates in these regions.

In addition to these components, also contains a large number of glial cells, structures that support and maintain the neurons.. Myelin is not the only substance associated with these glial cells, there is a great variety of these that serve to keep neurons functioning properly.

The tracts of the brain

Both inside and outside the central nervous system, the white matter is organized as bundles of nerve fibers. is organized in the form of bundles of nerve fibers.. The so-called tracts or projection nerve fibers send the information processed by the gray matter to the different body regions outside the brain. A second type of white matter fibers are the association fibers that connect different brain regions of the same hemisphere.. The third and last type corresponds to the interhemispheric commissures, which connect structures of different hemispheres.

Within the brain there are a large number of structures made up mainly of white matter. One of the most visible and remarkable is the corpus callosum, one of the interhemispheric commissures, of great relevance that joins the two cerebral hemispheres and transmits information between them.

When the white matter fails

As we already know, there are numerous disorders caused by damage to brain structures of a neurological nature. Considering that the speed of processing is largely due to the presence of myelin and the need for information to travel effectively and efficiently in order to coordinate our actions, the presence of damage to the white matter can cause disorders such as the following: fatigue, psychomotor slowness, muscular incoordination and weakness, blurred vision, difficulty remembering, deficits in executive functions and intellectual abilities are some of the frequent symptoms of white matter malfunction.

Some of the disorders that affect or are affected by the white matter are multiple sclerosis (in which there is an inflammation of the white matter that produces a demyelination of neurons), Alzheimer's disease and other dementias, adhd (in subjects with this disorder a lower amount of white matter has been observed) or dyslexia (difficulties with processing speed are linked).

Bibliographical references:

• Fields, D. (2008). White Matter Matters. Scientific American, p. 54.

• Tirapau-Ustarroz, J., Luna-Lario, P., Hernáez-Goñi, P., & García-Suescun, I. (2011). Relationship between white matter and cognitive functions. Journal of Neurology, 52 (12), 725-742.