Occipital lobe: anatomy, characteristics and functions

The cerebral cortex, which is the most iconic part of the brain and known for its folds and labyrinth shape, is not an organ in charge of performing a specific function. Rather, what happens is that different parts of the cerebral cortex are responsible for participating in different mental processes, although all of them work in coordination with each other.

For example, him occipital lobe, located in the part of the brain closest to the nape of the neck, is very different from frontal lobe (located in the part of the brain closest to the forehead) not only because of its shape and location and shape, but especially because of the functions that these two are responsible for lobes of the brain.

If the frontal has a very important role in executive functions and the initiation of deliberate actions, the occipital lobe has a very specific role that has to do with perception and, specifically, with the recognition and analysis of everything that we see. Next we will see the main characteristics of the latter part of the brain.

What is the occipital lobe?

The occipital lobe is one of the smallest lobes of the brain, and occupies a small portion of the back of the brain, between the cerebellum, the temporal lobe and the parietal lobe.

In addition, as with the rest of the lobes, it exists both in the Cerebral hemisphere left as well as right, which means that each person has two nearly symmetrical occipital lobes that are separated by a narrow fissure.

Unlike what happens with the frontal lobe, it is believed that throughout the evolution of the ancestors of our species the occipital lobe has not grown in proportion to the rest of parts of the brain. That is, while the rest of the areas of the cerebral cortex were developing and organizing in a more complex way, the occipital lobe has remained almost the same over hundreds of thousands of years; although, curiously, it is believed that in Neanderthals, which were an evolutionary branch parallel to that of Homo sapiens, this area was larger (relative and absolute) than that of our species.

Functions of this brain region

However... What is the occipital lobe in charge of and why has it not been growing throughout our evolutionary history? While there is no brain area It has only one function, since they all work together and in a coordinated way, the process that best defines the usefulness of the occipital lobe is the processing of visual information.

The occipital lobe comprises the visual cortex, which is the area of ​​the cerebral cortex where information from the retinas first reaches. In turn, the visual cortex is divided into several regions classified according to the level of processing they are responsible for.

Thus, the primary visual cortex (v1) is the part of the occipital lobe that processes the most "raw" visual data. and it is in charge of detecting the general patterns that can be found in the information collected by the eyes. These general and not very detailed data about what is seen are sent to other parts of the occipital lobe responsible for perform a more refined processing of vision and these, in turn, send the analyzed information to other areas of the brain.

The dorsal pathway and the lateral pathway

Once the information has passed through the primary visual cortex in the occipital lobe, the stream of data emitted by this area forks following two different routes: the ventral route and the dorsal route. These are spreading in parallel while communicating with parts of the brain that the other way does not access directly, as we will see.

Ventral route

The ventral pathway starts from the primary visual cortex in the occipital lobe and goes towards the frontal area of ​​the brain through the lower part of the brain, which includes the visual cortices V2 and V4 which, as indicated by its number, They are in charge of processing the information already worked on by v1.

It is considered that the neurons that participate in this "assembly line" of visual information they are in charge of processing the characteristics of the isolated elements that are being seen at all times, that is, about the content of the vision. For this reason, this route is also called the "what" way.

Dorsal route

This route goes from the occipital lobe to the frontal area of ​​the cerebral cortex through networks of neurons near the upper part of the skull. In it, the information processed by the primary visual cortex reaches the parietal lobe through the v3 and v5 visual cortices. This visual processing zone is believed is responsible for establishing the characteristics of the location and movement of what is seen; That is why the dorsal pathway is also called the "where and the" how.

Along with the ventral pathway, this visual processing pathway related to the occipital lobe tells us about how the brain works: sometimes, mental processes that seem to form a unity and that come to our consciousness as a complete experience, in reality they are the product of several brain pathways that work in parallel, each one focused on one aspect different.

The occipital lobe and epilepsy

The occipital lobe is believed to play a prominent role in the appearance of epileptic seizures, or at least part of them. These are cases in which exposure to frequent “flashes” of intense light causes the appearance of a pattern of emission of electrical signals by neurons of the occipital lobe that extends throughout the brain causing the attack.

Due to the complexity of the brain's functioning and the speed with which neurons work, not much is known about the mechanisms by which this occurs. type of epileptic seizures, although from these cases it is assumed that some external stimuli can cause a focus of epilepsy to appear in some part of the temporal lobes, which happens to affect other parts of the brain in the same way that the visual cortex sends information to other regions under normal conditions.

However, for these cases to occur it is believed that there must be a biological or genetic propensity.

In conclusion

Although the processing of data collected by the retinas is probably not the only function of the occipital lobe, is practically occupied by the visual cortex, and that is why it is believed that its main function has to do with the interaction of the information that comes from the optic nerves.

It may seem strange that a single sense claims for itself an entire lobe of each cerebral hemisphere, but it is not so strange when we consider that the lobe Temporal is the smallest in humans and that in mammals the processing of information collected by the eyes usually occupies very large areas of the body. brain. Ultimately, as descendants of an arboreal and diurnal evolutionary line, vision has been of great importance to both time to move through three-dimensional spaces full of dangers and obstacles as when detecting predators and food.

On the other hand, another of the most important aspects of the occipital lobe is that it is the beginning of the two parallel information processing pathways. This makes us better understand what the perceptual phenomenon of vision is like., which is presented through at least two separate information processing chains: on the one hand, the backbone, in charge of that we can know well the movement, position and location of what we see, and on the other the ventral path, related to the recognition of what we are seeing (that is, the integration of small image fragments into large units that we can identify).

Bibliographic references:

• Carlson, Neil R. (2007). Psychology: the science of behavior. New Jersey, USA: Pearson Education.
• Destina Yalçin, A.; Kaymaz, A.; Forta, H. (2000). "Reflex occipital lobe epilepsy". Seizure.
• Houdé, O. Mazoyer, B., Tzourio-Mazoyet, N. (2002). Cerveau et psychologie Introduction à l'imagerie cerébrale anatomique et fonctionnelle.
• Schacter, D. L., Gilbert, D. L. & Wegner, D. M. (2009). Psychology. (2nd ed.). New Work (NY): Worth Publishers.