Cerebral hemisphere neurophysiology

2021-06-16 03:40 PM

To study the functional areas of the cerebral cortex, people divide the cortex in different ways

Structural features

The cerebrum consists of two cerebral hemispheres, right and left, separated by the interhemispheric sulcus. Each cerebral hemisphere is surrounded by a layer of gray matter 2 to 4 mm thick called the cortex. The cerebral cortex is divided into four main lobes:

Frontal lobe.

Occipital lobe.

Top lobe.

The temporal lobe.

Functions of the cerebral cortex

The cerebral cortex is the centre of many important neurological functions:

Movement function.

Sensory function.

Botanical function.

Advanced neural function.

Each area of ​​the cerebral cortex corresponds to a certain function.

The cerebral cortex is also the centre of higher neural activities: thinking, feeling...

In this article, we only study the functional areas of the cerebral cortex, the higher neural activity will be covered in another chapter.

To study the functional areas of the cerebral cortex, people divide the cortex in different ways. Among them, Brodmann's way of dividing the cerebral cortex into 50 regions numbered from 1 to 50 is the most common.

Sensory regions

Visual area:

Including regions 17, 18, 19 belonging to the occipital lobes on both sides.

Zone 17:

As the normal visual field, this area gives us the perception of light and colour but does not allow us to perceive the visible object.

Zone 18, 19:

It is the perceptual visual area that allows us to perceive what we see.

When this area is damaged, you can see the object but do not know what it is.

Hearing area:

Including regions 22, 41, 42 belonging to the bilateral temporal lobes.

Areas 41, 42:

This is the normal auditory region, giving us the sensation of sound (raw sound). Damage to this area causes deafness.

Zone 22:

Is the auditory perception area, which allows us to perceive what kind of sound?

Taste area:

Belongs to area 43 of the parietal lobe.

Olfactory area:

Belonging to area 34 of the temporal lobe, this region belongs to the limbic system.

Sensory area

Belongs to zone 1, 2, 3 of the peak rally.

Motion zone

Belonging to the ascending frontal gyrus, this is the starting point of the tower bundle.

Compared with other regions, the motion zone has the largest area.

In addition, besides the motor area, there is a premotor area in the 6 frontal lobes, which is the place where the fibres go to the subcortical gray nuclei and then follow the extrapyramidal system to govern automatic movements.

The motor and sensory areas of the cerebral cortex have the following rules of operation:

Crossover rule:

One hemisphere of the brain controls the movement and sensation of the other half of the body.

Rule of precedence:

The organs that have a lot of movement and subtle sensations occupy a larger cortical area (hands, mouths, etc.).

Inversion rule:

The upper cortex governs the movement and sensation of the lower parts of the body. In contrast, the lower cortex governs the upper parts.

Speech zone

There are two regions related to speech:

Broca area:

Belongs to areas 44 and 45 of the frontal lobe.

This is the area that governs the movement of organs involved in vocal movements such as the larynx, lips, tongue...

When this area is damaged, they become mute but still understand words and words. The patient hears and reads and understands but cannot express his or her thoughts verbally. However, they can express themselves through writing.

Wernicke Region:

Located in the temporal lobe, this is a very important region in the formation of speech and thought. Therefore, also known as the language comprehension area, the comprehension area...

This area not only governs speech, but also allows us to understand words, understand words...

When Wernicke's area is damaged, he suffers from muteness accompanied by incomprehension of words, words...

The speech region is unevenly distributed in 2 hemispheres. In right-handed people (about 90%), Broca and Wernicke's areas develop very widely on the left hemisphere, the right hemisphere is negligible, and the left hemisphere is called the dominant hemisphere.

In left-handed people (accounting for 10%), the dominance of both hemispheres is equal. The number of hemispheric people must be very small.