Story of a woman who has always lived without a piece of her brain

Story of a woman who has always lived without a piece of her brain

In early February 2016, after reading in an article that two scientists at the Massachusetts Institute of Technology (MIT) were studying how the brain reacts to music, a woman felt the urge to send them an email: "I have a interesting brain, "he wrote in the message.

EG, who asked to be referred to only by initials to protect his privacy, does not have a left temporal lobe, a part of the brain believed to be involved in language processing. The woman's case, however, was not entirely suitable for the study of the scientists, who therefore decided to refer her to Evelina Fedorenko, a cognitive neuroscientist at MIT who studies language. It was the beginning of a fruitful collaboration. The first article on EG's brain was recently published in the journal Neuropsychologia, and Fedorenko's team plans to publish many more.

A brain different from the others The lack of a large part of the brain has surprisingly had an effect limited on the life of EG, who is in her fifties and raised in Connecticut, United States. EG has a degree, a remarkable career and she speaks Russian - as a second language - so well that she dreams in the language. She first discovered that she had an atypical brain in the fall of 1987, at George Washington University Hospital, when she underwent an MRI scan for an unrelated reason. The cause was probably a stroke when she was a child; today, in the area of ​​the brain that should be occupied by the left temporal lobe of the woman there is only cerebrospinal fluid. For the first ten, EG did not speak to any of her about her situation, apart from her parents and her two closest friends. Since then, she has confided in multiple people, but only a very small circle know of her unique brain anatomy.

Over the years, the woman says, doctors have repeatedly told her that her brain was incomprehensible. A doctor explained to her that she should have seizures and that she shouldn't have a good vocabulary, and "she was annoyed that she wasn't like that." EG has had several frustrating experiences: "They said a lot of things and jumped to conclusions without any investigation," he explains.

How our brain evolves over time Putting together a huge amount of MRI data, a team of researchers photographed the evolution of the brain: from fast growth in the early stages of life to "retirement" in old age Then EG met Fedorenko: "He had no preconception about what I should or should not be able to do" , remember. For Fedorenko, the opportunity to study a brain like EG's was every scientist's dream, and the woman was more than willing to help her.

Fedorenko's laboratory is trying to shed light on the development of the many regions of the brain that are thought to play a role in learning and understanding language, but the functioning of which is not yet fully understood. "We know very little about how the system develops," says Fedorenko. This is because to understand it it would be necessary to analyze the brains of children between one and three years old, whose language skills are still in the development phase. "We don't have the tools to probe the brains of children of that age," she adds.

When EG showed up at her laboratory, Fedorenko realized she had a valuable opportunity to understand how the remaining tissue in the The woman's brain had reorganized cognitive tasks. It is very rare for a person like EG to volunteer to be studied by scientists.

For most people, language processing occurs mostly in the left hemisphere of the brain. In some cases, the task is evenly divided between the two hemispheres. Even more rarely, the right hemisphere takes over most of the functions (scientists aren't entirely sure why this happens, but in left-handed people, "the language system probably resides in the right hemisphere," explains Greta Tuckute. , a doctoral student who works in Fedorenko's laboratory and is the lead author of the article).

Language processing occurs largely in two sections of the brain: the frontal and temporal regions. The temporal lobes develop first, followed by the frontal areas around the age of five. At this point, the linguistic network is considered fully mature. Since EG is missing the left temporal lobe, Fedorenko's team had the opportunity to answer an interesting question: are temporal regions a necessary requirement for the creation of the frontal linguistic areas?

The study In their first article devoted to the study of EG's brain, the scientists tried to understand if the woman showed signs of linguistic activity in the completely intact left frontal lobe. This would suggest that frontal speech areas can emerge even without a pre-existing temporal lobe in the same hemisphere.

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Arrow Researchers used functional magnetic resonance imaging, or fMRI, to detect EG brain activity while the woman performed certain language-related tasks , such as reading sentences. Scientists looked for evidence of linguistic activity in the left frontal lobe, and then compared brain activity with about ninety neurotypical controls (similar data obtained from subjects with intact left temporal lobes). Having found nothing, the researchers concluded that the presence of temporal areas of language appears to be necessary for the emergence of the frontal areas of language. However, Fedorenko's team found that the left frontal cortex of EG is perfectly capable of supporting high-level cognitive functions, an aspect that the researchers were able to confirm by asking the woman to perform math tasks while observing her brain's responses. They concluded that in the absence of the left temporal lobe, the task of language processing appears to have simply passed to the right hemisphere of EG. A single hemisphere, therefore, seems to be sufficient to guarantee the woman an advanced language ability.

An MRI of the brain of EG.

Evelina Fedorenko, Greta Tuckute / Brain and Cognitive Sciences La human brain resilience

The fact that the uniqueness of EG's brain has an extremely limited effect on his daily life demonstrates how large portions of our brain can be expendable. Fedorenko points to a surgical practice called hemispherectomy applied to children with epilepsy and unresponsive to drugs. The procedure involves removing half of the brain where the seizures occur, and infants on whom it has been practiced have been shown to retain normal cognitive function. "The fact that it is possible to remove half of the brain without major consequences suggests that there are a lot of redundant elements in our brain - explains Fedorenko -. From an engineering perspective, it is a pretty good way to build the system."

WiredLeaks, how to send us an anonymous report The reality is that when it is damaged, the brain often finds a way to reconfigure itself. It's something Ella Striem-Amit, a cognitive neuroscientist at Georgetown University, understands well. Striem-Amit studies the ways in which the brain reorganizes itself in the absence of some senses, for example in people born blind or deaf: "The remarkable thing about this patient - and other similar patients who lacked large parts of the language system from birth. , or other systems - is how well they compensate, "he says.

If the abnormality develops in childhood, when neuroplasticity is strongest, another part of the brain usually compensates for function of the missing portion forming new neural connections that take on the tasks. "There is extensive research conducted over decades showing that the brain is much more flexible early in life," says Striem-Amit.

The importance of case studies Drawing conclusions from observing a single person might seem premature. In recent years, studies involving individuals have begun to enjoy a bad name, as more limited searches can produce random results. In the field of research, there has been a widespread shift towards larger studies. But the case studies laid the foundation for modern neuroscience. There are several famous examples, as in the case of Broca's patient, who in 1861 illustrated to scientists which part of the brain controlled the production of language; or the patient H.M. , whose brain has solved the mystery of how memories are organized in the brain; and perhaps the most famous case, that of Phineas Gage, a railroad worker with whom an iron rod stuck in his brain in 1848 and whose personality changes after the accident would demonstrate for the first time how certain functions are associated to specific regions of the brain. "All the fundamental discoveries that led to our understanding of the brain began with case studies," says Striem-Amit.

Fedorenko argues that observing high-quality data in an individual is like "using a microscope. high precision instead of looking with a naked and myopic eye, when the only thing you see is a stain ". If done carefully, the approach can lead to groundbreaking discoveries, as in the case of EG, Fedorenko explains. "We can get an enormous amount of information from cases where there is a slightly different aspect - he adds -. It would be a shame not to take advantage of these accidents of nature". "It is really important to study unique cases - agrees Striem-Amit -. The trend is in the direction of big data, but we must emphasize the importance of deep data".

Future developments In the future, Fedorenko's laboratory hopes to learn much more from EG's brain. In a preliminary version of the article, which has not yet been peer-reviewed or published by a journal, the researchers explain that they examined a brain region called the visual word form area (Vwfa), which is thought to be responsible for decoding written words. In neurotypical individuals the region is found in the left inferior temporal cortex, but in the case of EG the function is distributed throughout the brain. For a future study, the researchers are also trying to understand how EG's missing temporal lobe affects her auditory system. Surprisingly, EG's sister does not have a right temporal lobe, again without great consequences. According to Fedorenko, this suggests that there is probably a genetic cause behind childhood strokes that may explain the absence of the brain regions. The team of researchers plan to study both EG and her sister - who she voluntarily agreed to undergo the studies - to try to understand how social and emotional processes take place predominantly in the right hemisphere. In fact, EG's entire family is involved in the study. A third brother and the woman's father also underwent a brain ultrasound, finding that they both had intact temporal lobes, or a "boring brain" as EG calls it. A fourth brother will be subjected to examination in the near future. For a long time, EG never thought that anyone would be interested in studying her, and she is glad that the neuroscience field could learn something about her from her brain. "I hope this will take away some of the negative associations associated with atypical brains," she adds.

This article originally appeared on UK.

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