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Scientists Claiming There's No Brain Growth After Age 13 Spark Fiery Debate

“They may just not have looked carefully enough."

It’s hard for us to accept the idea that the brain stops growing, despite the large body of scientific evidence supporting this idea. The often-repeated statistic, based on years of research, is that the brain stops developing around the age of 25. More recently, an international team of neuroscientists argued in Nature that the human brain stops producing new neurons at age 13. The response from the scientific community to this most recent study has been significant, to say the least.

In their paper, published Wednesday, the researchers write that their findings “do not support the notion that robust adult neurogenesis continues in the human hippocampus.” In other words, none of the hippocampus tissue samples from adult brains they examined showed evidence of new neurons. Infants’ brains grow lots of new neurons, they report, and older children’s brains slow down a little. Meanwhile, none of their adult samples showed evidence of new neurons. And this is what other scientists don’t agree with.

“They may just not have looked carefully enough,” Jonas Frisén, Ph.D., of the Karolinska Institute in Sweden, told STAT News on Wednesday. Frisén co-authored a paper in 2015 that contradicts the findings of the Nature paper. And Frisén isn’t the only one who thinks these researchers’ conclusion may be premature.

This image shows new neurons (green) in the brains of an infant (left), a 13-year-old (middle), and a 35-year-old (right).

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“There is a long history of concluding that adult neurogenesis doesn’t exist in a given species based on difficulty in identifying new neurons,” Heather Cameron, Ph.D., a principal investigator of neuroplasticity at the National Institutes of Mental Health, told The Atlantic on Thursday. “This happened in rats and then in nonhuman primates, both of which are now universally acknowledged as showing adult hippocampal neurogenesis.”

One of the major difficulties in measuring neurogenesis in the brain is that you can’t observe it in real time. The researchers, therefore, had to settle for the next best thing: brains from recently deceased patients. Unfortunately, even when directly examining brains, the best you can do is look for molecular markers that could indicate new neurons.

“You can’t just shine light onto a skull and see it,” said Salk Institute neurobiologist Fred Gage, Ph.D., who studies adult neuroplasticity, in an interview with STAT News on Wednesday. Therefore, this evidence comes down to how it’s interpreted. That’s where the disagreement lies.

Many in the scientific community are contesting the finding that the brain stops making new neurons after age 13.

Despite the uproar, the authors of the paper stood by their findings. “If neurogenesis continues in adult humans, it’s extremely rare,” Arturo Alvarez-Buylla, Ph.D., a neuroscientist at University of California, San Francisco and one of the authors on the study, told The Atlantic. “It’s not as robust as what people have said, where you could go running and pump up the number of neurons.”

In recent studies, neuroscientists have demonstrated that human adult brains can indeed produce new neurons, specifically in the hippocampus, a region associated with working memory, so Alvarez-Buylla and his team will likely need much more evidence to convince the community that their findings are correct. Plenty of research has shown that neuron development drops off as people get older, but moving the finish line back to age 13 is huge. There might not be any closure to this argument yet, but future experiments will hopefully clarify exactly at what age human brains stop producing neurons — if they ever do.

You Can Save Up to 30 Percent on Your Power Bill With Arcadia Power

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Filed Under Energy & Power

Given the chance, most of us would jump at the opportunity to bring down our power bills. But, there’s a prevailing assumption that doing so involves dealing with steep upfront costs before the savings actually come in. Arcadia Power presents a different solution, however, and it’s willing to give new users $20 off their first utility bill for trying out the platform.

Ancient Humans' Tiny Tool Use Is a Big Reason We Are Evolutionarily Unique 

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Tools have long been a centerpiece of humans’ ongoing quest to understand our own evolution. Man created tools, and so man has been judged as uniquely, cognitively complex. The problem with this line of thinking, however, is that it’s increasingly obvious that toolmaking and tool use do not make humans as unique as we’d like to think: Many animals, from orangutans to crows, make tools, too.

73 Years Later, the "A-Bomb" Ginkgo Trees Still Grow in Hiroshima

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On August 6, 1945, an Allied plane dropped an atomic bomb on Hiroshima, Japan, creating a fireball 1,200 feet in diameter. Disaster rained down upon the city, killing an estimated 150,000 people and leveling both the biological and man-made landscape. Little was left standing, but somehow the ginkgo trees were able to weather one of the most destructive moments in human history.

How a Brutal Murder Had a Profound Ripple Effect on Scientific Thought

A viral story of 38 do-nothing witnesses changed sociology, psychology, and neuroscience.

When 28-year-old Catherine Susan Genovese was killed outside her apartment in Kew Gardens, Queens, 38 people reportedly witnessed the attack but didn’t get involved.

Known to her friends as Kitty, she had only lived at 82-70 Austin Street for a year with her girlfriend, Mary Ann Zielonko, before returning on the night of March 13 from her job managing a bar.