Occipital Brain Lobe and Its Function

The occipital lobe participates in vision processing. It processes and interprets everything we see. The occipital lobe is also responsible for analyzing contents, such as shapes, colors, and movement, and also for interpreting and drawing conclusions about the images we see.

Boundaries, Anatomy, Position, and Structure of the Occipital Brain Lobe

The boundaries of the occipital lobe include the edges of the parietal and temporal lobe. The occipital lobe contains the primary visual cortex and associative visual areas (1).

The occipital lobe occupies the posterior parts of the hemispheres. On the convex surface of the hemisphere, the occipital lobe has no sharp boundaries separating it from the parietal and temporal lobes.

The exception is the upper part of the parietal-occipital groove, which, located on the inner surface of the hemisphere, separates the parietal lobe from the occipital lobe. The furrows and edges of the upper canopy of the occipital lobe are unstable and have a variable structure.

On the inner surface of the occipital lobe, there is a groove of spores, which separates the wedge (triangular norm of the occipital lobe) from the lingual gyrus and the occipital-temporal gyrus (1). 

In the occipital lobe of the cerebral cortex is, the following fields are positioned: 

• Area 17 - Gray matter buildup in a visual analyzer. This field is the primary zone. It is made up of 300 million nerve cells.
• Area 18 - It is also a nuclear set of visual analyzers. This field performs the function of perceived writing and is a more complex secondary area. 
• Area 19 – This field is involved in evaluating the value of what we see. 
• Area 39 - This brain part does not completely belong to the occipital region. This area is located at the border between the parietal, temporal, and occipital lobes. Its functions include integrating visual, auditory, and general sensitivity of information (1).

The Function of the Occipital Brain Lobe

The function of the occipital lobe is related to the perception and processing of visual information, as well as the organization of complex processes of visual perception.

At the same time, the upper half of the retina, which detects light from the lower field of vision, is projected into a wedge; in the reed area, the gyrus is the lower half of the retina, noticing the light from the upper field of view(1).

In the occipital cortex, there is a primary visual area (the cortex of the part of the sphenoid gyrus and the lingual lobule). There is a local representation of the retinal receptors. Each retinal point corresponds to its portion of the visual cortex, while the yellow dot area has a relatively large representation area.

In connection with the incomplete intersection of visual pathways, the same half of the retina is projected into the visual area of each hemisphere. The presence of retinal projection of both eyes in each hemisphere is the basis of binocular vision.

The neurons of these zones are polymodal and respond not only to light but also to tactile and auditory stimuli. Different types of sensitivities are synthesized in this visual area, more complex visual images emerge and they are recognized.

An example can be given to understand the function of the occipital lobe in visual perception. When we look at a map and "put" the route planner information into our working memory, the first step would be to process millions of light stimuli in the recognition centers, i.e. to process different signals perceived by the photosensitive cells of our retina. 

Furthermore, the occipital lobe receives incoming information, which is processed and immediately sent to the hippocampus, where it is formed into memory. Firstly, it becomes short-term memory. Accordingly, we remember the name of the place of destination and remember it as we move along this route.

As we have already stated, the occipital lobe is responsible for the visual perception of information, as well as its operational storage. Generally, everything projected by the retina is recognized and formed into a specific image in the occipital lobe.

For absolutely healthy people, this proportion works independently and flawlessly, but irreparable consequences can occur with injuries and some illnesses. Sometimes, total blindness can occur. This is the process that happens if there is a damage on the surface of the primary visual cortex.

Light signals transmit information to the occipital lobe via nerve endings, which represents a form of irritation or stimuli for the retina. The nerves then transmit information to the diencephalon, another part of the brain. And diencephalon, in turn, sends information to the primary visual cortex, called the sensory cortex.

From the primary sensory cortex, nerve signals are sent to the adjacent areas and are called sensory associative cortex areas. The main function of the occipital lobe is to send signals from the primary visual cortex to the visual associative cortex. The areas described together analyze the visual information observed and retain visual memories. 

As already implied, this occurs when the primary visual cortex, whose surface is visible, is damaged. Complete damage to the primary cortex occurs in three cases, as a result of a head injury, as a result of the development of a tumor on the surface of the brain, and finally, yet very rarely, as a consequence of certain congenital anomalies.

Damage of the Occipital Brain Lobe

Damage to the primary visual cortex leads to a form of central blindness called the Anton's syndrome; patients cannot recognize objects via their sense of sight and are completely unaware of their deficits (2).

Epileptic seizures in the area of the occipital lobe cause visual hallucinations, most commonly in the form of dashes and a colored mesh that appears on the contralateral field of view.

Damage of the occipital brain lobe can occur as a result of a head injury, a tumor on the surface of the brain, and certain congenital anomalies. 

However, focal lesions do not lead to complete loss of vision. For example, after taking a familiar object in his hands, a patient may describe the object he/she is touching. However, if that same object is shown in the picture, then the patient will not be able to describe its shape and color. In medical language, this condition is called visual agnosia. 

At times, focal lesions can localize and restore vision and perception. However, it is important to note that the chances of a partial recovery in children are higher than those in patients whose brain is already formed and not growing anymore. Treatment is usually done surgically(2).

Pain in the occipital brain lobe region

There are many different causes of pain in this region. Some of them include:  

• Nerve tension and stress. With prolonged tension, neck and back muscle spasms and neck pain occurs. Also, pain in the occipital brain region can be localized. The patient can diminish the pain by breathing calmly and deeply. If the pain does not stop after the patient feels relaxed, a visit to a doctor is obligatory. 
• Osteochondrosis of the cervical spine. This condition results in sharp pain in the back of the head. Specialized forms of gymnastics can help. However, the patient must see a neurologist. 
• High blood pressure. This condition can cause pain with a feeling of fullness. Pressure control is essential for extending one’s lifetime. Contact a neurologist if you feel pain in the occipital part of your brain and suffer from blood pressure disorders. 
• Increased intracranial pressure. This serious condition is characterized by oppressive eye pain. The pain is localized in the occipital lobe. The patient must immediately see a doctor.

Conclusion

The occipital lobe is located in a triangle, the apex of which is the parietal lobe and the sides of the temporal lobes of the brain. The cerebellum is positioned below the occipital lobe. This brain part has a variable structure.

Its key function is processing visual information. The visual cortex, located on both hemispheres of the occipital lobe, provides binocular vision - the world seems vast and wide to the human eye. 

The visual cortex, called the associative area, constantly communicates with other brain structures, forming a complete image of the world. The occipital lobe has strong links with the limbic system (especially the hippocampus), the parietal, and temporal lobes.

Thus, this or that visual image may be accompanied by negative emotions or vice versa: long-term visual memory may evoke positive emotions.

The occipital lobe, along with simultaneous signal analysis, also plays the role of an information container. However, the amount of such information is insignificant, and most of the environmental information is stored in the hippocampus.  

The occipital cortex is strongly associated with feature integration. The essence of these theories is that the cortical analytic centers of separate properties of an object (color) are processed separately, and in parallel with the processing of other information.

To sum up, the occipital lobe is responsible for processing visual information and their integration into the general relation to the world; storing visual information; interaction with other areas of the brain, and, partly, tracking their functions; as well as the binocular perception of the environment.

References:

1. Rehman A, Al Khalili Y. Neuroanatomy, Occipital Lobe. [Updated 2019 Jul 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544320/  Found online at: https://www.ncbi.nlm.nih.gov/books/NBK544320/
2. Macaskill J. A CASE OF OCCIPITAL LOBE INJURY. Br J Ophthalmol. 1945 Dec;29(12):626-8. PMID: 18170164; PMCID: PMC512175.  Found online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC512175/