The telencephalon consists of two hemispheres and a middle part connecting the two hemispheres. The part of the surface of the cerebral hemisphere is called the cerebral cortex.

The cortical surface is covered with grooves with different depths, which are called cerebral sulcus, and the protruding part between the sulcus is called cerebral gyrus. The total weight of human cerebral cortex accounts for about 4% of the total brain weight, covering an area of more than 2, square centimeters, of which 1/3 (about 75 square centimeters) is exposed on the surface, and 2/3 is located at the groove wall and groove bottom.

The sensitivity of the brain can be praised with a thumbs up. It sometimes takes only one thousandth of a second from receiving a "signal" to issuing a "command".

The brain is a biological universe with complex structure, clear hierarchy, strict hierarchy and clear division of labor. The two hemispheres of the human brain are highly specialized in some advanced functions.

Generally speaking, the left hemisphere is related to abstract thinking, symbolic relations and logical analysis of details. It can talk, write and calculate, and has the ability of language, analysis and continuous calculation. It is more like a ruler, plays an active leading role in controlling the nervous system, and is a meticulous and serious external executive body. The right hemisphere is often taciturn. Generally speaking, it can't keep in touch with the outside world, and it gives the right to drive behavior to the left hemisphere. The right hemisphere is related to perception and sense of spatial position, and can handle single things, but not continuous mathematical sequences. However, it is endowed with a special talent, that is, it is good at thinking in images. He is a master of art and a pioneer full of passion for invention and creation. It has musical, painting, comprehensive, holistic and geometric space discrimination ability.

Because most of the language functions are concentrated in the left hemisphere, it has the opportunity to get on the command desk of the three armed forces. Therefore, for a long time, people have unanimously called it the dominant hemisphere, while the humble, silent and introverted right hemisphere has been dismissed as the inferior hemisphere. In fact, the right hemisphere is obviously superior to the left hemisphere in many aspects, especially in concrete thinking ability, creative thinking ability, thinking ability of space composition and understanding of complex relationships. The right hemisphere is a talented band conductor, who is brilliant in explaining auditory-sound impression and understanding musical characteristics; The right hemisphere has a unique eye for expressing emotions and identifying emotions. The subtle handling of these emotions depends on the right hemisphere. In fact, the obscure right hemisphere is at the advanced level of human thinking, sensing, thinking, and learning and remembering with emotion; It holds the present and dreams of the future. As the important functions of the right hemisphere are constantly revealed, the dominance of the left hemisphere will definitely end, and the "dominant hemisphere theory" will eventually be replaced by the "functional asymmetry theory of the two hemispheres of the brain".

There are frontal, temporal and parietal regions on the left and right hemispheres of the brain, which are called "lobes" in medicine.