Occipital lobe: anatomy, characteristics and functions.

We review all the details and functions of this lobe of the brain.

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

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

If the frontal lobe 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 we see. Below 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 lobes of the brain.It occupies a small portion of the back part of the brain, between the cerebellum, the temporal lobe and the parietal lobe.

Moreover, as with the other lobes, it exists in both the left and right cerebral hemispheres, 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 the parts of the brain. That is, while the other areas of the cerebral cortex were developing and organizing themselves in a more complex way, the occipital lobe has grown in proportion to the rest of the brain, the occipital lobe has remained almost unchanged over hundreds of thousands of years. over hundreds of thousands of years; although, curiously, it is believed that in the Neanderthals, who were an evolutionary branch parallel to Homo sapiens, this area was larger (relative and absolute) than that of our species.

Functions of this brain region

Now then... what is the occipital lobe responsible for and why has it not been growing throughout our evolutionary history? While no area of the brain has only one function, as they all work together in a coordinated fashion, the process that best defines the utility 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 information from the retinas arrives first. 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 not very detailed data about what is seen are sent to other parts of the occipital lobe in charge of a more refined processing of vision and these, in turn, send the analyzed information to other areas of the brain.

The dorsal and lateral pathways

Once the information has passed through the primary visual cortex in the occipital lobe**, the stream of data emitted by this area bifurcates along two different routes: the ventral pathway and the dorsal pathway**. They run in parallel while communicating with parts of the brain that the other pathway does not access directly, as we shall see.

Ventral pathway

The ventral pathway 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 which, as their number indicates, are in charge of processing the information already processed by v1..

It is considered that the neurons that participate in this "assembly chain" of visual information are in charge of processing the characteristics of the isolated elements that are being seen at each moment, i.e. about the content of the vision.that is to say, about the content of the vision. For this reason, this pathway is also called the "what" pathway.

Dorsal pathway

This pathway runs from the occipital lobe to the frontal area of the cerebral cortex through networks of neurons near the top of the skull. Here, information processed by the primary visual cortex reaches the parietal lobe via the v3 and v5 visual cortexes. is believed to be responsible for establishing the characteristics of the location and movement of what is seen.This is why the dorsal pathway is also called the "where and how" pathway.

Together 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 unit and reach our consciousness as a complete experience are actually the product of several brain pathways working in parallel, each focused on a different aspect.

The occipital lobe and epilepsy

The occipital lobe is believed to play a prominent role in the occurrence 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 electrical signal emission by neurons in the occipital lobe that spreads throughout the brain causing the seizure.

Due to the complexity of the functioning of the brain 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 may cause a focus of epilepsy to appear in some part of the temporal lobes, which then affects other parts of the brain in the same way that the visual cortex sends information to other regions under normal conditions.

However, for such cases to occur, it is believed that there must be a Biological or genetic propensity to epilepsy..

In conclusion

Although the processing of data collected by the retinas is probably not the only function of the occipital lobe, it is practically occupied by the visual cortexand therefore its main function is thought to have to do with the interaction of information coming from the optic nerves. 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 if we take into account that the temporal lobe is the smallest in humans and that in mammals the processing of information gathered by the eyes 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 for moving through three-dimensional spaces full of dangers and obstacles and for 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 pathways of information processing. This gives us a better understanding of the perceptual phenomena of vision.This is presented by at least two separate chains of information processing: on the one hand, the dorsal pathway, which is responsible for the movement, position and location of what we see, and on the other, the ventral pathway, which is related to the recognition of what we are seeing (i.e., the integration of small image fragments into large units that we can identify).