The perietal lobe is one of the four lobes that make up the cerebral cortex . Others are the frontal , temporal, and occipital lobes. There is one each in both hemispheres of the brain, left and right. The parietal lobe is located at the top of the middle of the head, just behind the frontal lobe and above the occipital and temporal lobes. Its border with the frontal lobe is the central sulcus, its border with the occipital lobe is the parieto-occipital sulcus and its border with the temporal lobe is largely formed by the lateral sulcus (sylvian fissure). The right and left parietal lobes are separated from each other by the medial longitudinal fissure.
It plays a central role in the perception and integration of senses such as touch, sight, taste, smell and hearing. This is the primary sensory area where the sensory signals from the body are interpreted. As a result of the researches, it has been seen that as the sensory stimulus from a certain part of the body increases, more areas are allocated to that region in the parietal lobe. For example, in a person who is busy with the senses coming from the fingers, a wider brain region is concerned with the finger sense.
Some functions of the parietal lobe:
- Two-point sense distinction. Without looking at something touched, do not distinguish whether it is one or two pieces.
- Identifying where the sense of touch comes from.
- Integration of sensory data with other areas of the brain.
- Visual-spatial orientation and reasoning. The parietal lobe is activated in situations such as following directions, reading maps, and overcoming unexpected obstacles on the road. In addition to these, it is also important in the sense of knowing the position of different parts of the body, called proprioception. For example, being able to touch the nose with the tip of the index finger when our eyes are closed is through the sense of proprioception.
- It carries out some functions related to vision together with the occipital lobe.
- To evaluate numerical relations, to know the number of objects seen.
- To evaluate the size, shape and placement of seen and remembered objects.
- Mapping the visual world. Special parts of the parietal lobe function as a map of the visual world.
- Coordination of hand, arm and eye movements.
- Language processes.
- Coordination of attention.
Some Important Structures in the Parietal Lobe
Postcentral gyrus: This area is the primary sensory cortex of the brain. The sensory homonculus is a region where the sensory data of the body are processed and each body part is represented by a certain cortex area. Also known as Brodmann’s 3rd field.
Posterior parietal cortex: plays a vital role in coordinating movements and spatial reasoning. It provides the attention triggered by new stimuli, such as an animal leaping onto the road while driving.
Superior parietal lobule: Allows the person to orient himself and other objects with respect to the environment. It is thought to help coordinate fine skills, as it also receives significant stimulation from the hands.
Inferior parietal lobule: Also known as the Gerschwind area, this area helps evaluate facial expressions and emotions. They may also have tasks in different areas such as language processing, simple mathematical operations, body perception. Angular and supramarginal gyrus are also here.
How Does the Parietal Lobe Affect the Body?
Each sub-region of the brain performs its functions in relation to other parts and the body. The parietal lobe also uses sensory data from the whole body to work. Various sensory stimuli that come constantly are made sense in the parietal lobe. It also establishes strong connections with the occipital lobe. Thus, functions such as visual perception and direction determination are performed. The functions of different parts of the cerebral cortex do not remain constant throughout life. It can vary based on experience. When there is a brain injury, the healthy segments can take over the duties of the damaged segments. The adaptive ability of the brain is called plasticity . Physical therapy and rehabilitation in the early period after problems such as stroke and trauma increase the rate of recovery.
What Happens in Damage?
Symptoms due to parietal lobe damage vary according to the location and size of the damage. The recovery process depends on the cause, how early the diagnosis is made and the treatment applied. Causes such as stroke, brain hemorrhage, trauma, tumor, infection can lead to brain damage. Symptoms of parietal lobe damage may include:
- In right parietal lobe damage, the person may not be able to pay attention to the left half of his body. In the so-called neglect syndrome , one half of the environment and the body is neglected. It can be evaluated by methods such as clock drawing and star deletion test.
- Gerstmann syndrome can be seen in left parietal lobe damage. The person may experience loss of skills such as writing, calculation and language. The inability to distinguish right and left, and the inability to recognize fingers are also distinctive findings.
- Damages affecting both parietal lobes can cause Balint syndrome. Movement skills and visual attention are impaired. The person may not be able to fix their eyes voluntarily. May have difficulty integrating the components of a landscape, may not be able to reach out and use the object without looking at it.