Most of us have heard about the gray matter in one person or another. In Spain it is a concept that has been popularly associated with intelligence, but in reality its role is much more important than that.

Grey matter can be found in the brain, yes , and furthermore its existence has to do with the way in which mental processes related to, among other things, cognition and intelligence are developed. But having more or less grey matter does not imply being more or less intelligent. This is because its function is more general and essential, and it has to do with the basic functioning of the nervous system.

What is grey matter?

The grey matter, also called grey substance, comprises the areas of the central nervous system in which the somas of the neurons predominate (i.e. the part of the neuron in which its nucleus is located and its “body” from which the branches start).

The grey colour of these areas is in contrast to the white of the rest of the nervous system, which has that aspect because the axons of the neurons, that is, the extensions that are born of the somas and are covered by myelin, are predominant in them and are white in colour.

In qualitative terms, there are no relevant differences between the composition of the white matter and the grey matter: in both there are neuronal somas, dendrites and axons with myelin. However, there are significant differences in the quantities and proportions in which these elements are present in each of them .

So, technically, grey matter is not a part of the brain, but the material with which some parts of the brain are built.

The distribution of the grey substance

The areas of the brain and spinal cord that are made up of gray matter do not form a homogeneous whole, but are spread out and in some cases there is white matter between them.However, in most cases these areas are large enough to be easily distinguished with the naked eye.

In the medulla, the grey matter is in the central and lateral part (in any of its sections, regardless of the height), but in the brain it is more distributed.

The cerebral cortex, for example, is made up of grey matter , but the same is true of the basal ganglia, which are located below, the deepest and most superficial part of the cerebellum and many other scattered areas, such as the thalamus and hypothalamus.

The function of these areas

Unlike white matter, where myelin causes nerve impulses to be transmitted rapidly through axons, gray matter cannot make the information flowing through it go as fast. The main function of these areas is not to make electricity pass through them quickly , but it has to do with the processing of information, whatever kind it is.

As the information content processed by the grey matter areas is very diverse, the effects of a decrease or an increase of this substance are also varied. That is why injuries in these areas depend on the type of structure they affect. However, no part of grey matter can work without the help of white matter, as they need to be connected to each other to function properly.

The grey matter of the spinal cord acts as an information directory , i.e. it decides what information enters and exits the nerves of the peripheral nervous system and what information should travel up or down the spinal cord. In addition, there are some theories about memory according to which memories are stored chemically within the neuronal somas, which are much more abundant in this type of brain tissue.

Concluding

The presence of grey matter tells us that the part of the brain in which it is located receives information from many areas of white substance and that, in some way, they function as information processing clusters and in which the nerve impulses that travel through the axons meet a relay that directs them to another destination.

This implies, among other things, that grey matter and white matter are needed to work as they should; not for nothing are they two types of brain tissue differentiated by the concentration of the part of the neurons that predominate most in them (axons or somas), and these small nerve cells form an organic unit that cannot be separated without destroying it.