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 a body responsible for performing a specific function. What happens, rather, is that different parts of the cerebral cortex are responsible for participating in different mental processes , although all of them work coordinating with each other.
For example, him occipital lobe , located in the part of the brain closest to the nape, is very different from the frontal lobe (located in the part of the brain closest to the forehead) not only by its shape and location and shape, but especially by the functions of These two lobes of the brain are in charge.
If the frontal has a very important role in the 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 we see. Next we will see the main characteristics of this last part of the brain.
What is the occipital lobe?
The occipital lobe is one of the smallest brain lobes , and occupies a small portion of the back part of the brain, between the cerebellum, the temporal lobe and the parietal lobe.
In addition, as with the rest of the lobes, it exists in both the left and right cerebral hemispheres, which means that each person has two almost 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 the 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 the Neandertals, which were an evolutionary branch parallel to that of Homo sapiens, this area had a larger size (relative and absolute) than that of our species.
Functions of this brain region
However... What is the occipital lobe responsible for and why has it not been growing throughout our evolutionary history? While there is no area of the brain that has only one function, since all of them function together and in a coordinated manner, 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 to which the information coming from the retinas first arrives. 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 is responsible for detecting the general patterns that can be found in the information collected by the eyes. These general and little detailed data about what is seen are sent to other parts of the occipital lobe in charge of carrying out a more refined processing of the vision and these, in turn, send the analyzed information to other areas of the brain.
The dorsal and lateral routes
Once the information has passed through the primary visual cortex in the occipital lobe, the torrent of data that this zone emits bifurcates following two different routes: the ventral route and the dorsal route . These are extending in parallel while communicating with parts of the brain that the other route does not directly access, as we will see.
The ventral route starts from the primary visual cortex in the occipital lobe and goes to the frontal area of the brain through the lower part of the brain, which includes the visual cortexes V2 and V4 that, as indicated by their number, They are responsible for processing the information already worked by the v1 .
It is considered that the neurons involved in this "assembly line" of visual information are responsible for processing the characteristics of the isolated elements that are being viewed at any time , that is, about the content of the vision. Therefore, this route is also called the "what" route.
This route goes from the occipital lobe to the frontal zone of the cerebral cortex through networks of neurons near the top of the skull. In it, the information processed by the primary visual cortex reaches the parietal lobe through the visual cortexes v3 and v5. It is believed that this area of visual processing is responsible for establishing the characteristics of the location and movement of what is seen ; that's why the dorsal track is also called the "where and how" way.
Next to the ventral route, this route of visual processing related to the occipital lobe tells us about how the brain works: sometimes, mental processes that seem to form a unit and come to our consciousness as a complete experience, are actually the product of several brain routes that work in parallel, each focused on a different aspect.
The occipital lobe and epilepsy
It is believed that the occipital lobe plays a prominent role in the appearance of epileptic seizures, or at least in 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.
Because of the complexity of brain function and the speed with which neurons work, not much is known about the mechanisms by which this type of epileptic seizures appear, although from these cases it is assumed that some external stimuli can cause it to appear a focus of epilepsy somewhere in 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. But nevertheless, for these cases to occur, it is believed that there must be a biological or genetic propensity .
Although probably the processing of the data collected by the retinas is not the only function of the occipital lobe, it is practically occupied by the visual cortex , and for that reason 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 if we consider that the temporal lobe is the smallest in humans and that in mammals the processing of the collected information Through the eyes it usually occupies very large areas of the brain. After all, as descendants of an arboreal and diurnal evolutionary line, vision has been very important both when it comes to moving through three dimensional spaces full of dangers and obstacles and 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 ways of processing information. This makes us know better how is the perceptual phenomenon of vision , which is presented by at least two separate chains of information processing: on the one hand the dorsal path, responsible for knowing 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).