What happens in the areas of the brain dedicated to the vision of people blind from birth?

In France, there are just over 200,000 blind people, born or not. Knowing that a large part of our brain is used for vision, how does the brain of these people work? In people blind from birth, the areas of the brain normally attributed to vision are not inert, quite the contrary! They are stimulated during tasks other than vision, such as language and memory. On the other hand, the nature of the information that triggers these activations is not well known.

In people blind from birth, the visual cortex is totally reorganized

A team of the Paris Brain Institute has looked into this question. To better understand what is happening in the visual cortex of people who were born blind, the researchers used two brain imaging techniques: magnetoencephalography (MEG) and imaging by nuclear magnetic resonance (MRI) functional. MRI maps the functional activities of the brain but does not reflect activity in real time. MEG makes it possible to record the magnetic activity of the brain in real time. It makes it possible to know which areas of the brain are activated when the subject performs an action.

I’Functional MRI made it possible to observe the reorganization of the cortex vision in people blind from birth. For example, areas usually dedicated to vision are assigned to memory in blind people and this area is linked to that devoted to memory in sighted people.

The MEG provides even more interesting information. Patients blind from birth heard a list of words and had to categorize them: plant, animal or object. As the patient categorized the word, the visual cortex would light up differently depending on the category being uttered. The visual cortex is therefore involved in the understanding of speech.

How is the visual cortex activated?

In sighted people, the visual cortex activates based on information from eyes. What happens to people who are blind from birth? Information from the ears or from touch passes through the hearing or touch regions of the brain before reaching the area of ​​vision, via links established between the different regions. These links do not exist in sighted people.

As summarized the author“ it is an outstanding example of plasticityillustrating the brain’s ability to functionally reorganize itself in an unusual situation, where a whole part of the brain is not supplied with the type of information it usually receives “.