Shock for scientists - a man lives without 90% of the brain

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

Magnetic resonance imaging of a patient with virtually no brain, but leading a normal social life. Photo: Feuillet et al./The Lancet

A French man living a relatively normal and healthy life, despite the absence of 90% of the brain, forces scientists to reconsider theories about the biological essence of consciousness.

Despite decades of research, experts still cannot explain the phenomenon of consciousness - the fundamental way in which a person relates to the world. We know that this something is formed in the brain, based on neurons. But how is consciousness preserved if the vast majority of neurons are absent?

For the first time described in the scientific journal Lancet, a clinical case has been discussed in the scientific community for almost ten years.

At the time of admission to the clinic, the patient was 44 years old, and until that moment he did not do a tomogram and did not know that he had practically no brain. The scientific article does not reveal the identity of the patient to maintain confidentiality, but the scientists explain that he lived most of his life quite normally, without even knowing about his peculiarity.

The man's brain scans were done almost by accident. He came to the hospital complaining of weakness in his left leg, but the doctor sent him for a tomogram. The MRI results showed that the man's skull was almost completely filled with fluid. Only a thin outer layer with the medulla remains, and the inner part of the brain is practically absent.

The illustration on the left shows a CT scan of a patient's brain with a large part of the skull filled with fluid. For comparison, the tomogram on the right shows the skull of a normal brain without abnormalities.

Scientists believe that the patient's brain was slowly destroyed over 30 years as fluid accumulated, a process known as hydrocephalus (dropsy of the brain). He was diagnosed as a teenager and underwent bypass surgery to restore the movement of cerebrospinal fluid, but at the age of 14, the shunt was removed. Since then, the fluid in the skull accumulated, and the brain was gradually destroyed.

Despite this, the man was not recognized as mentally retarded. He does not have a very high IQ of 75, but this did not stop him from working as a civil servant, getting married and having two children.

When the story of an unusual patient was published in the scientific press, it immediately attracted the attention of neuroscientists. It is surprising that a person with such an anamnesis generally survived, and even more so was conscious, lived and worked normally.

At the same time, this case made it possible to test some theories about human consciousness. In the past, scientists have suggested that consciousness can be associated with various specific areas of the brain, such as the claustrum (fence) - a thin (about 2 mm thick) irregular plate, consisting of gray matter and located under the cerebral cortex deep in the white matter. Another group of researchers from Princeton University put forward the theory that consciousness is associated with the visual cortex. But the history of the French patient casts great doubt on both of these theories.

“Any theory of consciousness should be able to explain why such a person who lacks 90% of their neurons still exhibits normal behavior,” says Axel Cleeremans, a cognitive psychologist at the Free University of Brussels, Belgium. The scientist gave a lecture at the 20th International Conference on the Scientific Study of Consciousness in Buenos Aires in June 2016.

“Consciousness is a non-conceptual theory of the brain about itself, gained through experience - through learning, interaction with oneself, with the world and other people,” says Axel Cleiremans. In his scientific work, the scientist explains that the presence of consciousness means that a person not only has information, but also knows about the fact that he has information. In other words, unlike a thermometer, which shows temperature, a conscious person both knows the temperature and cares about this knowledge. Clearemans claims that the brain is continuously and unconsciously learning to re-describe its own activity to itself, and these reports of "self-diagnosis" form the basis of conscious experience.

In other words, there are no specific regions in the brain where consciousness “lives”.

Axel Cleiremans first published his theory in 2011. He calls it the "radical plasticity statement" of the brain. This thesis is quite consistent with the latest scientific research, which shows the unusual plasticity of the adult brain, capable of recovering from trauma, "reprogramming" certain areas for new tasks, to restore consciousness and full performance.

Cleremance's theory may explain the case of a French man who retains consciousness in the absence of 90% of his neurons. According to the scientist, even in this tiny brain, the remaining neurons continue to describe their own activity, so that a person gives an account of his actions and retains consciousness.

Our knowledge of how the brain works is increasing every year. Despite the principle "No system can create a system more complex than itself", we gradually study the work of the central nervous system and learn to reproduce its functions. For example, just a few days ago, a scientific work was published describing how a blind mouse partially restored vision by building up ganglionic (nerve) cells in the retina - the part of the nervous system between the brain and the eye.

More and more discoveries are taking place in this area. True, sometimes there is a strange feeling that the more we learn about the work of the brain, the more complex its structure seems to be.

Read also about other cases: Life without a brain