Occipital lobe: anatomy, characteristics and functions

The cerebral cortex, which is the most iconic part of the brain and known for its folds and labyrinthine shape, is not an organ tasked with performing a specific function. What happens instead is that different parts of the cerebral cortex are responsible for participating in different mental processes, Although they all work in coordination with each other.

For example, the occipital lobe, Located in the part of the brain closest to the neck, is very different from the frontal lobe (located in the part of the brain closest to the forehead) not only for its shape and location and shape, but above all for in charge of these two brain lobes.

If the frontal plays a very important role in executive functions and the initiation of deliberate actions, the occipital lobe has a very specific role which has to do with perception and, more precisely, with the recognition and analysis of everything. what we see. Below we will look at the main features of this 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 part of the back of the brain, between the cerebellum, temporal lobe and parietal lobe.

In addition, as with the rest of the lobes, there are in the left and right cerebral hemispheres, which means that each person has two almost symmetrical occipital lobes separated by a narrow slit.

Unlike the frontal lobe, it is believed that during the evolution of the ancestors of our species, the occipital lobe did not increase in proportion to the rest of the brain. In other words, while the other areas of the cerebral cortex developed and organized themselves in more complex ways, the occipital lobe has remained almost the same over hundreds of thousands of years; although, oddly enough, it is believed that among the Neanderthals, who 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 responsible for and why has it not grown throughout our evolutionary history? While no area of ​​the brain has a single function because they all work together and in a coordinated fashion, the process that best defines the utility of the occipital lobe is the processing of visual information.

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

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 general patterns that can be found in information gathered by the eyes. This general and inaccurate data about what is seen is sent to other parts of the occipital lobe responsible for performing more refined vision processing and these, in turn, send the analyzed information to other areas of the body. brain.

The dorsal approach and the lateral approach

Once the information has passed through the primary visual cortex to the occipital lobe, The torrent of data emitted by this zone branches off following two different routes: the ventral route and the dorsal route. These extend in parallel because they communicate with parts of the brain that the other path does not directly access, as we will see.

via ventral

The ventral tract leaves 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 cortex V2 and V4 which, as indicated by their number, they are in charge of processing the information already processed by v1.

Neurons are considered to be involved in this “assembly line” of visual information they are responsible for processing the characteristics of isolated elements that are viewed at any given timeIn other words, on the content of the vision. Therefore, this route is also referred to as the “what” route.

dorsal approach

This pathway runs from the occipital lobe to the frontal area of ​​the cerebral cortex through neural networks near the top of the skull. In it, information processed by the primary visual cortex reaches the parietal lobe through visual cortices 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; this is why the dorsal route is also called the “where and how” route.

Along the ventral pathway, this visual processing pathway linked to the occipital lobe teaches us about the functioning of the brain: sometimes mental processes which seem to form a unit and come to our consciousness as a complete experience, are actually the product of several brains. parallel course, each focused on a different aspect.

The occipital lobe and epilepsy

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

Due to the complexity of how the brain works and the speed at which neurons work, not much is known about the mechanisms by which this type of epileptic seizure occurs, although from these cases we assumes that some external stimuli can cause an outbreak of epilepsy to appear somewhere in the temporal lobes, which affects other parts of the brain in the same way that the visual cortex sends information to other areas under normal conditions .

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

To conclude

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 cortex, And that is why it is believed that its main function is related to the interaction of information from optic nerves.

It may seem strange that a single sense claims for itself an entire lobe of each cerebral hemisphere, but this is not so much when one considers that the temporal lobe is the smallest in humans and that now the mammals The processing of information collected by the eyes generally 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 allows us to better understand what the perceptual phenomenon of vision looks like, Which is presented through at least two distinct chains of information processing: on the one hand the dorsal pathway, responsible for knowing the movement, position and location of what we see, and on the other share the ventral path, related to the recognition of what we see (that is, the integration of small image fragments into large units that we can identify).

Bibliographical references:

  • Carlson, Neil R. (2007). Psychology: the science of behavior. New Jersey, United States: Pearson Education.
  • Destina Yalçinn, A .; Kaymaz, A .; Forta, H. (2000). “Reflex epilepsy of the occipital lobe”. Confiscation.
  • Houdé, O. Mazoyer, B., Tzourio-Mazoyet, N. (2002). Brain and Psychology Introduction to anatomical and functional brain imaging.
  • Schacter, DL, Gilbert, DL and Wegner, DM (2009). Psychology. (2nd ed.). New Work (New York): Worth Publishers.

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