The cerebral cortex is located on the surface of the brain and although its thickness is only four millimeters, the cortex makes up as much as 40% of the mass of the entire brain. In the cortex of the brain, there are numerous nerve cells that are responsible for sensation and for controlling movements. It is because of the complex functions of the cerebral cortex that its damage usually leads to very serious difficulties. What disturbs the functions of the cerebral cortex and what symptoms indicate its damage?

The cerebral cortex(akacerebral cortex) is part of the gray matter of the nervous system - it consists of numerous cells nerve impulses (their number can reach up to 16 billion), which are responsible for receiving, sending and processing various nerve impulses.

The cerebral cortex itself is quite thin - in humans it is usually 2 to 4 mm thick - its surface, however, is relatively large, as it can even reach 0.25 square meters.

It may seem almost unbelievable, but it is possible due to the folding of the cortex of the brain.

Cerebral cortex: types

There are basically two types of cerebral cortex in humans. The first is the mammalian neocortex, which covers 90% of the brain's surface and has a six-layer structure.

The second is the much less extensive old cortex, which can be found primarily within the structures that make up the limbic system and in the forebrain. Ancient cortex is found in the brain of mammals and lower vertebrates, and usually has less than 6 cell layers.

Cerebral cortex: layered structure

Taking into account the fact that the majority of the cerebral cortex is formed by the neocortex, it is definitely worth taking a closer look at its structure. As mentioned above, it has 6 layers, which are:

  • particulate layer: the outermost layer in which relatively few nerve cells are present; located in the particle layer are single horizontal Cajal neurons, as well as fibers of pyramidal neurons and associative (associative) fibers
  • outer granular layer: there are numerous pyramidal and stellate cells within it
  • outer pyramid layer: the most characteristic for it are numerous pyramidal cells, additionally inin this layer, granular cells as well as basket and spindle cells are present in small amounts
  • inner granular layer: it is a thin layer of the neocortex, in which numerous granular cells are located, it is also characterized by the fact that there are many bunches of horizontal nerve fibers in it
  • inner pyramid layer: there are large pyramidal cells in it, in addition to them in the inner pyramid layer there are also giant Betza cells
  • layer of polymorphic cells: the innermost layer of the neocortex with numerous polygonal neurons (mainly triangular and spindle neurons)

Cerebral cortex: functional division

The division of the cerebral cortex into the new and the old cortex is definitely not the only functioning division of this part of the brain - the functional division of the cerebral cortex is also popular. In this case, the following are listed:

  • motor cortex: it is located within the pre-central gyrus, in the anterior part of the peri-medial lobe and in part of the superior, middle and inferior frontal gyrus; it is responsible for generating nerve impulses that enable people to make various movements
  • sensory cortex: it occupies the medial gyrus and the posterior part of the parietal lobe, and its centers are also located in the superior parietal lobe; Additionally, within the sensory cortex, there are areas responsible for the reception and analysis of specific stimuli, they are the visual cortex (located within the occipital lobe) and the auditory cortex (located in the superior temporal lobe)

Within the cerebral cortex, there are also several associative areas that are responsible for the integration of nerve stimuli reaching the cerebral cortex.

As it is easy to guess, in order for the cerebral cortex to function properly, it must have numerous connections with various parts of the nervous system.

Most of the impulses that are originally picked up at various receptors throughout the body go to the cerebral cortex via the thalamus.

Centers that are located in a given hemisphere of the brain deal with receiving impulses from the opposite half of the body - more precisely, sensory stimuli from the right side of the body are analyzed in the left hemisphere of the brain and vice versa.

It should be clearly emphasized when discussing the functions of individual parts of the cerebral cortex that the cortex located in the left and right cerebral hemispheres may function as separate,specialized functions.

Within the dominant hemisphere (which in most Europeans is the left hemisphere of the brain) there are cortical centers responsible for speech, the ability to perform various calculations or receive and interpret various sensory stimuli.

In the structures of the non-dominant hemisphere, there are centers related to spatial imagination or three-dimensional perception of the surrounding reality.

Cerebral cortex: functional centers

One more division of the cerebral cortex, which still finds practical use in medicine, should definitely be mentioned here. This is a division that was proposed at the beginning of the last century by a German-born neurologist, Korbinian Brodmann.

Based on the cellular structure of individual regions of the cerebral cortex, he distinguished several dozen areas, which are now referred to as Brodmann fields. The researcher specified the following fields and functions:

  • 1, 2, 3 - surface feeling
  • 4 - free movement
  • 5 - astereognosia
  • 6 - limb and eyeball movement control
  • 7 - analyzing motor and visual stimuli
  • 8 - eye movements
  • 9, 10, 11, 12 - awareness and thinking
  • 17, 18 - vision
  • 19 - picking up colors and movements
  • 20-21- spatial vision
  • 22 - speech sensory center
  • 23, 24, 25, 26, 27, 29, 30, 31, 32, 33 - emotions and memory
  • 28, 34, 35, 36, 38 - sense of smell
  • 37 - reading, speaking, seeing
  • 39 - seeing, reading, counting, distinguishing between the sides of the body
  • 40 - planning complex movements, facial expressions
  • 41,42 - hearing
  • 43 - flavor
  • 44, 45 - speech motor center
  • 46 - behavior, thinking, planning eyeball movements

The absence of some fields may be puzzling, incl. fields from 13 to 16 - their absence is not a result of a mistake, but it follows that in the division of the cerebral cortex proposed by Brodmann, these fields simply… do not exist.

Cerebral cortex: causes and effects of damage

Damage to the cortex of the brain may occur in connection with many different pathological processes.

It happens that the patients themselves cause it - the abuse of various harmful substances, including excessive alcohol consumption or smoking can lead to progressive damage to the cerebral cortex.

A stroke may also result in the death of its nerve cells, in addition, dysfunctions in various parts of the cerebral cortex may appear in patientsstruggling with some neurological diseases (including neurodegenerative diseases or multiple sclerosis).

Various intracranial neoplasms can also lead to the degradation of the cerebral cortex.

It is simply impossible to list all possible symptoms of cerebral cortex damage - patients may experience various types of ailments depending on which parts of this structure will be damaged.

It is possible to experience sensory disturbances as well as difficulties with performing free movements. It happens that patients experience problems with understanding speech (when the sensory center of speech is damaged), as well as difficulties with independent expression (occurring when there is a degeneration of the speech motor center).

Vision or hearing impairment, and the occurrence of seizures in patients are possible. This is where the clinical significance of distinguishing Brodmann fields appears - when the doctor knows which brain regions are responsible for which activities, on the basis of the patient's complaints, he can conclude which part of the brain has been damaged by the cerebral cortex.

Category:

Anatomy