The parietal lobe, a potential ally in the fight against Alzheimer's

That the brain is a fascinating organ is not a mystery. For the Greek physician and philosopher Hippocrates, it was the “throne” of intelligence, experience and consciousness, and perhaps he was right. It is the cradle of thought, reason and language. He is the puppeteer who pulls the strings so that we carry out actions that are as simple as eating our grandmother's beloved paella or running to catch the bus. It helps us discriminate certain sound qualities in our environment and, ultimately, allows us to enjoy life.

Unfortunately, nothing lasts forever and some brain areas, such as the parietal lobe, suffer deterioration in Alzheimer's disease. This lobe is responsible for mainly processing somatosensory information, that is, it handles data about touch, movement and the position of our body in relation to space. In addition, it also processes cognitive and multimodal information (that comes from different sensory modalities).

The parietal lobe is so important that some researchers point out that reduced blood flow in this area could serve as a biomarker to detect Alzheimer's in its earliest stages.

Neuroplasticity in vision loss
As a person ages, problems following a conversation in a noisy restaurant or detecting a smell or taste become more acute. However, the most commonly known sensory deficit that occurs with age is vision loss. This does not prevent us from remembering that both vision deficits and blindness are problems that are present at all ages and throughout the world.

In people with visual impairment, the parietal lobe does not deteriorate, but rather undergoes remodeling as a result of brain neuroplastic mechanisms. These mechanisms are nothing more than the ability of nervous tissue to strengthen its connections and create new ones. It is well known that this neuronal plasticity can arise after injury and as a consequence of experience.

Neuroplasticity helps us understand why hours of practice with the organ made Johann Sebastian Bach a great musician and composer. After all, our brain does not sit still, it is not static, but dynamic.

But why does this happen? What is the reason why the parietal lobes of people with visual loss present this neuronal deployment? What stimulates you? Well, we must think that people with reduced vision capacity need to interact daily with their environment without the help of their sense of sight. Therefore, they rely more on their sense of touch to recognize objects, they practice reading texts in Braille and they can move around thanks to the use of a white cane.

All of the above would strengthen your neuronal connections in favor of the parietal lobe. Thus, it has been observed that in people with visual loss the parietal connections with the occipital lobe are reinforced, which is proof of so-called neuroplasticity.

The role of the parietal lobe in Alzheimer's, under examination
There is research that links visual loss with the onset of Alzheimer's, but these were not free of serious methodological limitations. This is where an alternative hypothesis arises whose main character, the missing piece in the puzzle, would be the parietal lobe.

In our research, published in the Journal of Alzheimer's Disease, we start from the theory that adaptive changes in the nervous system and, more specifically, in the parietal lobe, could make people with visual functional diversity less susceptible to experiencing neurodegenerative diseases than involve deterioration of said lobe, such as Alzheimer's.

This hypothesis could represent an advance in the way of understanding both Alzheimer's and the brain changes that follow visual loss. Well, it is not only important to research curative treatments for neurodegenerative diseases, but it is also of interest to understand their pathophysiology. It is, therefore, in the hands of science to reveal this mystery and tip the balance in favor or against the proposed hypothesis.

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Source: The Conversation. Authorship:

Mónica Alba Ahulló Fuster
Doctoral student and researcher in the Department of Radiology, Rehabilitation and Physiotherapy / Faculty of Nursing, Physiotherapy and Podiatry, Complutense University of Madrid

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