Figure | PopCap
Many doctors were puzzled by the results of her brain imaging. Because, according to their understanding, such brain defects should lead to serious functional deficits. Finally, she couldn’t bear the doctors who made rash comments, and contacted a scientific research team, hoping to use the power of scientists to solve the mystery of her brain. Scientists are also a treasure trove…
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It wasn’t until she was 25 that she knew her brain was a little different from the average person.
If it wasn’t for that brain scan that made her realize that there was a missing piece of her brain, she might never have discovered the secret. Because from childhood to adulthood, her daily life did not seem to be affected in any way, and she went to university step by step and even went to graduate school.
The left temporal lobe is missing, the left side of this image is the left brain, and the right side is the right brain | Original paper
The brain area she is missing is the left temporal lobe. For most people, this is a key area that carries language functions, and the corresponding location in her brain is just cerebrospinal fluid. A doctor once thought that her vocabulary would not exceed that of a fifth-grade pupil, but in fact she was in the top 2% of the population on a verbal IQ test. Not only that, her mother tongue is English, and she is also proficient in Russian as a foreign language.
Over the years, many of the doctors she has seen could not believe that such a unique brain could perform so well. At the same time, she became more curious about her own brain. Finally, in 2016, she contacted a team of scientists at the Massachusetts Institute of Technology (MIT), who also became their treasured research object.
Recently, the first paper on her (brain) was published, under the pseudonym EG. Scientists discovered some secrets in the development of language areas from her mind.
Left brain is not enough, right brain can make up
The human brain is divided into left and right hemispheres, each with four lobes: the frontal lobe in the front and the temporal lobe in the Laterally, the parietal lobe is superior, and the occipital lobe is posterior.
Figure | Wikimedia Commons
Among them, language function is mainly realized by the temporal and frontal lobes. The temporal lobe carries an important area called the Wernicke’s Area, located at the junction of the temporal lobe and the parietal lobe, that helps us understand language, whether it is what we hear or see There is also an important area in the frontal lobe called Broca’s Area, which can choose the right words for us to express our thoughts.
Both left and right brains have temporal and frontal lobes, but the two hemispheres function differently. For most people (85~90%)the left hemisphere will become the main responsibility for processing language and become the dominant hemisphere, while the function of the right hemisphere language area is will be inhibited.
If you remember, it was the temporal lobe of the left brain that the protagonist EG lost. However, her language skills are not obviously flawed, and even better than ordinary people (except for spelling errors). Therefore, scientists cherish this case that came to the door very much.
Left Temporal Lobe | Wikimedia Commons
In EG’s memory, she has never suffered any head trauma, or the defect in her brain is likely congenital. A common cause of this phenomenon is perinatal stroke (perinatal stroke): refers to a stroke that occurs in the fetus or infant between the 140th day of pregnancy and the 28th postpartum day. The research team believes that the absence of the left temporal lobe of the EG may also be due to this disorder.
The human brain has a certain degree of resilience in the face of early injury. In previous studies, some scientists have observed that after perinatal stroke, some children do not develop aphasia like the stroke patients in our general impression, but develop language similar to ordinary people ability.
This is because the neuroplasticity of humans is relatively strong in infancy. When one brain area is damaged, other brain areas can also establish new neural connections to complete the corresponding tasks and make up for the missing functions. There have been some cases to prove that the right hemisphere can take over the function of language when the left hemisphere is damaged in the early stage. This suggests that in young brains, both the left and right hemispheres are actively performing language processing tasks. In other words, at that time, the left hemisphere had not really dominated and become the dominant hemisphere, and the right hemisphere had a chance to ascend.
Since previous scientists have known that the human brain has a “redundant” setting, damage to one area still has the opportunity to substitute other areas . So, what new discoveries can the research team from MIT find in EG’s mind?
Without the temporal lobe, what about the frontal lobe?
The adult brain requires a frontotemporal network to process language. However, scientists didn’t know much about how this language network came about.
Before encountering the special case of EG, scientists often struggled to obtain the brain data of children aged 1-3 years, and this stage is the main period of language ability development; 4-5 There is a lot of data on children aged 20 to 20 years old and even in early adolescence, but those brains have developed to a level close to that of adults. If there is a significant difference, it means that the functional specialization of the left and right brains has not been completed, but it is difficult to provide researchers with information about development. Process inspiration.
For example, the function of the frontal lobe language area usually develops to a level similar to that of an adult around the age of 5;The temporal lobe language area is more developed than the frontal lobe language area. Early. Scientists have always been curious, is the existence of the language area in the temporal lobe a prerequisite for the generation of the language area in the frontal lobe?
With EG’s brain, the research team can design experiments to find out. They gave EG some reading tasks while relying on fMRI (functional magnetic resonance imaging) to monitor her brain activity and compare it with the brain activity of 94 adults with normal brain development. The 94 controls were also native English speakers, like EG.
True and False Sentence Examples | Original Paper
Specifically, the task is to read true sentences and false sentences. In the true sentence, each word is an actual English word, and it is arranged in a meaningful combination; in the false sentence, each “word” can be read according to the spelling, but it is not an actual English word, nor Can’t express any meaning.
True or false sentences, each sentence is 12 words long. Instead of appearing directly on the screen, each sentence pops up word for word, with a gap of 450 milliseconds between the two words. All EG and other controls had to do was read the sentences silently. The task targeted brain regions associated with lexical semantic processing and combination processing, the researchers said.
During the experiment, scientists mainly observed the left frontal lobe of the EG to see if there was language-related neural activity in this area. If there is, it means that the left frontal lobe can still develop language functions in the absence of the left temporal lobe. That is to say, the same hemisphere does not need to have the temporal lobe to produce the frontal language area. If not, it may indicate that the left frontal lobe did not develop language function in the absence of the left temporal lobe. In other words, in order to produce the frontal language area, the temporal lobe must exist in the same hemisphere.
R is right brain, L is left brain; blue is temporal lobe, pink is frontal lobe; a is left and right brain with complete temporal lobe, b is left temporal lobe missing | Original paper< /p>
As a result, the research team found no language activity in the left frontal lobe of the EG, while both the frontal and temporal language areas of the right brain were working. Scientists speculate from this that the presence of the temporal lobe in the same hemisphere is a necessary condition for the production of the frontal lobe language area. In the absence of the left temporal lobe in the EG, even if the frontal lobes of the left and right brains are connected to each other, the left frontal lobe cannot obtain language functions.
So, could it be that the left frontal lobe of the EG is not responding to any higher cognitive tasks? The team also tested the EG with some addition arithmetic problems, and the results showed that the left frontal lobe of the EG still retained other advanced cognitive functions, but lacked language functions. As a result, scientists are increasingly confident in their own judgment that the frontal language area cannot exist independently of the temporal language area (in the same hemisphere).
EG’s frontotemporal language network, all provided by the right hemisphere of her brain. This also means that one hemisphere is enough to ensure her intact language function.
Start with a special case
Of course, one person’s situation is not representative of another. The organic damage to EG’s brain did not cause her developmental delay, which does not mean that similar damage to the brains of other children will not cause developmental delay. This case study is just the beginning.
However, many important discoveries in neurology also begin with a single case. For example, as mentioned above, there is an important area in the frontal lobe called Broca’s area, which is responsible for language production. The area was named after a doctor named Pierre Paul Broca. In the 1860s, Dr. Broca first discovered a lesion in the left frontal lobe after the death of a patient who could only pronounce the sound “tan”, and later in his 20s A similar area of damage was found in the brain of one patient with similar symptoms. From this, he proved one thing: The function of the brain is indeed regionalized, and different brain regions are responsible for different functions.
Broca District | Wikimedia Commons
After more than ten years, a neurologist named Carl Wernicke also followed in Broca’s footsteps. Some patients who can speak fluently but cannot understand what they are saying have found damage in another area of the brain. That’s Wernicke’s area, located in the temporal lobe (which also extends to the parietal lobe) and helps in receiving and understanding language.
Today, MIT scientists continue to study the EG brain. Since the temporal lobe is not only responsible for language functions, it is also involved in some auditory perception. Next, the research team intends to continue to observe how the loss of the left temporal lobe affects the auditory system of the EG.
In addition to this, EG herself mentioned that in addition to missing a piece of her brain, she also lost a part of her brain stem. Years ago, a doctor had told her that she had only seen something like this in the brains of dead babies, and thought that any damage to the brain stem would be fatal. However, with the development of brain imaging technology, the situation like her is becoming more and more common.
Now, EG is over fifty years old, but she still hopes that as a special case, she can help people understand more possibilities of the brain.
“My brain is unique, not abnormal!”
References
Original paper:
https:https://www.sciencedirect.com/science/article/abs/pii/S0028393222000434?via%3Dihub
Reference link:
https:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6291004/
https:https://www.pnas.org/doi/10.1073/pnas.1905590117
https:https://www.wired.co.uk/article/she-was-missing-a-chunk-of-her-brain-it-didnt-matter