(I) Sensory Areas of the Cerebral Cortex and Their Functions
1. Visual Area: Located in the occipital lobe, it generates primary forms of vision. If this area is damaged, even if the eyes function normally, a person will completely lose their vision and become blind.
2. Auditory Area: Located in the temporal lobe, it generates primary forms of hearing. If this area is damaged, even if both ears function normally, a person will completely lose their hearing and become deaf.
3. Somatosensory Area: Located in the parietal lobe, it receives sensory information from the skin, muscles, and internal organs, generating sensations such as touch, temperature, pain, and movement.
- The projection relationship between different body parts and their corresponding sensory areas is as follows:
(1) Crossed representation, inverted top-bottom, and upright head;
(2) The size of the projection area of each body part is proportional to its importance in terms of function.
(II) Motor Areas of the Cerebral Cortex and Their Functions
The motor area is located in the anterior part of the precentral gyrus and the adjacent middle frontal gyrus (frontal lobe). It sends out motor commands, governing and regulating the movements of various parts of the body, as well as the body's position and posture in space.
The relationship between the motor area and different body parts is as follows:
(1) Crossed representation, inverted top-bottom, and upright head;
(2) The size of the corresponding area for each body part is proportional to its importance in terms of function.
(III) Language Areas of the Cerebral Cortex and Their Functions
The language areas are mainly located in the left hemisphere of the brain. They consist of extensive brain regions, including several important areas, as detailed in Chapter 8 "Language".
(IV) Lateralization of Brain Hemispheres
The brain is divided into left and right hemispheres, each of which has sensory areas, motor areas, visual areas, auditory areas, and association areas. Under normal circumstances, the two hemispheres coordinate their activities.
The corpus callosum is the part that connects the left and right hemispheres, allowing information to be transmitted and unified responses to be made. Each hemisphere only responds to stimuli from the opposite side of the body and regulates the movements of the contralateral body.
The functions of the two brain hemispheres are asymmetric. The left hemisphere is mainly responsible for language, reading, writing, mathematical calculations, logical reasoning, etc., while the right hemisphere is mainly responsible for perceiving spatial relationships of objects, emotions, artistic appreciation, dance, sculpture, etc. Under normal circumstances, the two hemispheres of the brain both have specialized functions and work together to complete complex tasks.
In the 1960s, Sperry conducted experiments on patients who had undergone corpus callosotomy, further confirming the asymmetry of functions between the two brain hemispheres. It should be noted that the lateralization of brain hemisphere functions is not absolute.