The forebrain is divided into two hemispheres (right and left), which are connected by the corpus callosum. The lower surface of the hemispheres is called the base of the brain.
The developed cerebral hemispheres in humans cover the entire midbrain and diencephalon.
Such mental functions as memory, speech, thinking, creative processes, personal qualities are associated precisely with the cerebral hemispheres. The functions of the left and right hemispheres are not equal. The right hemisphere is responsible for imaginative thinking, the left one for abstract thinking. In case of damage to the left hemisphere, the person’s speech is impaired.
The gray matter forms the cerebral cortex. White matter forms the pathways of the hemispheres. The nuclei of the gray matter (subcortical structures) are scattered in the white matter.
The activity of all human organs is controlled by the cerebral cortex. The cerebral cortex is formed by the bodies of neurons that cover the entire forebrain with a thin layer. The surface area of the cortex is about 2000–2500 cm² (this is due to the presence of a large number of grooves and convolutions). The bark provides a connection between the body and the external environment, is the material basis of human mental activity.
Deep grooves divide each hemisphere into 4 lobes: frontal, parietal, temporal, and occipital. Between the grooves are the folds of the cerebral cortex – gyrus.
The frontal lobes, separated from the parietal lobes by a deep central groove, reach the greatest development in humans. Their mass is about 50% of the mass of the brain.
Information from different senses comes to the frontal lobes of the cerebral cortex. Here the information is processed and the goal and program of action are formed. Such zones of the cortex are called associative, their development determines a person’s ability to learn. With the destruction of the frontal lobes, a person cannot establish a relationship between the sound and the letter with which it is designated, between the object and its name.
In the temporal lobes are the centers of hearing, taste and smell, and in the occipital – the visual centers.
In the cerebral cortex, the following sensitive and motor zones are distinguished:
– the motor zone is located in the anterior central gyrus of the frontal lobe;
– the zone of musculocutaneous sensitivity is located in the posterior central gyrus of the parietal lobe;
– the visual area is located in the occipital lobe;
– the auditory zone is located in the temporal lobe;
– the centers of smell and taste are located on the inner surfaces of the temporal and frontal lobes.