Language Neurons - Inner Voice? - Chimeroids - Migraines & Auras
Breedlove, S
https://www.nature.com/articles/d41586-024-02146-6
Ultra-detailed brain map shows neurons that encode words’ meaning
By Sara Reardon
By eavesdropping on the brains of living people, scientists have created the highest-resolution map yet of the neurons that encode the meanings of various words1. The results hint that, across individuals, the brain uses the same standard categories to classify words — helping us to turn sound into sense.
The study is based on words only in English. But it’s a step along the way to working out how the brain stores words in its language library, says neurosurgeon Ziv Williams at the Massachusetts Institute of Technology in Cambridge. By mapping the overlapping sets of brain cells that respond to various words, he says, “we can try to start building a thesaurus of meaning”.
The brain area called the auditory cortex processes the sound of a word as it enters the ear. But it is the brain’s prefrontal cortex, a region where higher-order brain activity takes place, that works out a word’s ‘semantic meaning’ — its essence or gist.
Previous research2 has studied this process by analysing images of blood flow in the brain, which is a proxy for brain activity. This method allowed researchers to map word meaning to small regions of the brain.
But Williams and his colleagues found a unique opportunity to look at how individual neurons encode language in real time. His group recruited ten people about to undergo surgery for epilepsy, each of whom had had electrodes implanted in their brains to determine the source of their seizures. The electrodes allowed the researchers to record activity from around 300 neurons in each person’s prefrontal cortex.
© 2024 Springer Nature Limited
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Not Everyone Has an Inner Voice Streaming Through Their Head
By Simon Makin
Most of us have an “inner voice,” and we tend to assume everybody does, but recent evidence suggests that people vary widely in the extent to which they experience inner speech, from an almost constant patter to a virtual absence of self-talk. “Until you start asking the right questions you don’t know there’s even variation,” says Gary Lupyan, a cognitive scientist at the University of Wisconsin–Madison. “People are really surprised because they’d assumed everyone is like them.”
A new study, from Lupyan and his colleague Johanne Nedergaard, a cognitive scientist at the University of Copenhagen, shows that not only are these differences real but they also have consequences for our cognition. Participants with weak inner voices did worse at psychological tasks that measure, say, verbal memory than did those with strong inner voices. The researchers have even proposed calling a lack of inner speech “anendophasia” and hope that naming it will help facilitate further research. The study adds to growing evidence that our inner mental worlds can be profoundly different. “It speaks to the surprising diversity of our subjective experiences,” Lupyan says.
Psychologists think we use inner speech to assist in various mental functions. “Past research suggests inner speech is key in self-regulation and executive functioning, like task-switching, memory and decision-making,” says Famira Racy, an independent scholar who co-founded the Inner Speech Research Lab at Mount Royal University in Calgary. “Some researchers have even suggested that not having an inner voice may impact these and other areas important for a sense of self, although this is not a certainty.”
Inner speech researchers know that it varies from person to person, but studies have typically used subjective measures, like questionnaires, and it is difficult to know for sure if what people say goes on in their heads is what really happens. “It’s very difficult to reflect on one’s own inner experiences, and most people aren’t very good at it when they start out,” says Charles Fernyhough, a psychologist at Durham University in England, who was not involved in the study.
© 2024 SCIENTIFIC AMERICAN,
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Brain ‘chimeroids’ reveal person-to-person differences rooted in genetics
By Charles Q. Choi
Chimeroids—brain organoids grown from the cells of multiple people—offer scientists a novel way to compare individual differences in response to drugs, infections or pathogenic variants, according to a new study in Nature.
“The possibilities are endless,” says lead investigator Paola Arlotta, professor and chair of stem cell and regenerative biology at Harvard University.
The approach overcomes a longstanding issue that has plagued any comparison of organoids derived from different people: Disparities between the organoids might reflect genetic dissimilarities between individual people but could also result just from inadvertent variations in how each organoid was grown, says Aparna Bhaduri, assistant professor of biological chemistry at the University of California, Los Angeles, who did not contribute to the new study.
Mixing cells from multiple donors into a single organoid makes it possible to grow all the cells under the same conditions and makes it more likely that any differences seen between the cells are rooted in genetic variations between the people, Bhaduri says.
Initially, Arlotta’s team tried to produce chimeroids by mixing pluripotent stem cells from multiple donors. But one person’s cells usually outgrew the others to make up most of each organoid. Even small differences in the stem cells’ extremely high growth rates easily led one person’s cells to overshadow the others, the team noted.
So instead, the researchers grew the stem cells independently in organoids until they began to proliferate more slowly as neural stem cells or neural progenitor cells. They then broke these organoids apart and mixed them together, producing the chimeroids that developed with balanced numbers of up to five donors’ cells. Each cell line in the chimeroids could produce all the cell types normally found in the cerebral cortex, Arlotta and her colleagues discovered using DNA and RNA sequencing techniques.
© 2024 Simons Foundation
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https://www.science.org/content/article/migraine-aura-trigger-headache
How does a migraine aura trigger a headache?
By Rodrigo Pérez Ortega
It starts with blind spots, flashing lights, and blurry vision—a warning of what’s to come. About an hour later, the dreadful headache kicks in. This pairing, a shining visual experience called an aura and then a headache, happens in about one-third of people who live with migraine. But researchers haven’t been able to figure out exactly how the two are linked at the molecular level. Now, a new study in mice, published today in Science, establishes a direct mechanism: molecules traveling in the fluid that bathes the brain. The finding could lead to new targets for much-needed migraine treatments.
“It’s exciting,” says Rami Burstein, a translational neuroscientist at Harvard Medical School who was not involved in the new study. “It takes a very large step into understanding how something that happened in the brain can alter sensation or perception,” he says. It may also explain why the pain of migraine is experienced only in the head, he adds.
Migraine, a debilitating neurological disorder, affects about 148 million people worldwide. Recently developed medications can help reduce headaches but are not effective for everyone. Although exact causes remain elusive, research has shown migraines most likely start with a pathological burst of neural activity. During an aura before a migraine, researchers have observed a seizurelike phenomenon called cortical spreading depression (CSD), in which a wave of abnormal neural firing slowly travels throughout the brain’s outer layer, or cortex.
But because the brain itself contains no pain-sensing neurons, signals from the brain would have to somehow reach the peripheral nervous system—the nerves that communicate between the body parts and the brain—to cause a headache. In particular, they’d have to get to the two lumps of neurons below the brain called the trigeminal ganglia, which innervate the two sides of our face and head. Scientists knew that pain fibers from the trigeminal ganglion were nested in the meninges—the thin, delicate membranes that envelop and protect the brain.
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https://www.nytimes.com/2024/07/06/health/brain-donation.html
Your Brain Holds Secrets. Scientists Want to Find Them.
By Paula Span
About a month ago, Judith Hansen popped awake in the predawn hours, thinking about her father’s brain.
Her father, Morrie Markoff, was an unusual man. At 110, he was thought to be the oldest in the United States. His brain was unusual, too, even after he recovered from a stroke at 99.
Although he left school after the eighth grade to work, Mr. Markoff became a successful businessman. Later in life, his curiosity and creativity led him to the arts, including photography and sculpture fashioned from scrap metal.
He was a healthy centenarian when he exhibited his work at a gallery in Los Angeles, where he lived. At 103, he published a memoir called “Keep Breathing.” He blogged regularly, pored over The Los Angeles Times daily, discussed articles in Scientific American and followed the national news on CNN and “60 Minutes.”
Now he was nearing death, enrolled in home hospice care. “In the middle of the night, I thought, ‘Dad’s brain is so great,’” said Ms. Hansen, 82, a retired librarian in Seattle. “I went online and looked up ‘brain donation.’”
Her search led to a National Institutes of Health web page explaining that its NeuroBioBank, established in 2013, collected post-mortem human brain tissue to advance neurological research.
Through the site, Ms. Hansen contacted the nonprofit Brain Donor Project. It promotes and simplifies donations through a network of university brain banks, which distribute preserved tissue to research teams.
Tish Hevel, the founder of the project, responded quickly, putting Ms. Hansen and her brother in touch with the brain bank at the University of California, Los Angeles. Brain donors may have neurological and other diseases, or they may possess healthy brains, like Mr. Markoff’s.
“We’re going to learn so much from him,” Ms. Hevel said. “What is it about these superagers that allows them to function at such a high level for so long?”
© 2024 The New York Times Company
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