Left-handedness - Reactive Amygdalas - Alzheimer's Drug? - Omega-3s

0 views

Skip to first unread message

Breedlove, S

unread,

Jul 15, 2026, 5:59:30 AM (8 days ago) Jul 15

https://www.quantamagazine.org/why-am-i-left-handed-20260713/

Why Am I Left-Handed?

By Natalie Wolchover

When I was first learning to write, my letters and words ran from right to left, reversed as if in a mirror. Being left-handed, I was imitating the hand strokes of my right-handed teachers instead of reversing their strokes to replicate the letters. I gradually got the hang of writing in the correct direction, but it still feels natural for me to mirror-write. I have a mirror-written childhood diary. Leonardo da Vinci, another lefty, did that too.

Being left-handed is mostly no big deal. It is annoying how ink smudges under my hand. And I did once have to jump out of the way of a circular saw that I was holding backward; indeed, left-handers have more accidents while operating machinery. That aside, overall, I enjoy being left-handed. It grants entry into a smug little club, whose members — 10% of the human population — carry the secret knowledge that we are overrepresented among U.S. presidents, famous artists and musicians, and top athletes.

But our difference hasn’t always been welcome. My 91-year-old Texan grandmother remembers starting out left-handed (she, too, has examples of mirror-writing from early childhood) before being forced to switch, a common practice in much of the world until about the 1970s. The deep-seated disdain for left hands runs through our very language. “Left” comes from Old English lyft, meaning weak, foolish, worthless, or useless, while “right” means correct or proper. In other languages, the word for “left” can also mean awkward, unlucky, clumsy, suspicious, or sinister.

In philosophy, “qualia” refers to the subjective qualities of our experience: what it’s like for Alice to see blue or for Bob to feel delighted. Qualia are “the ways things seem to us,” as the late philosopher Daniel Dennett put it. In these essays, our columnists follow their curiosity, and explore important but not necessarily answerable scientific questions.
© 2026 Simons Foundation

--------------------

https://www.sciencenews.org/article/left-right-dominance-practice-writing

Whether lefty or righty, practice makes the difference

By Laura Sanders

Babies are born with a natural preference for using their left or right side. Now, a new study suggests that preference alone doesn’t explain the dominant side’s superior skills: They come from practice.

The results, published June 30 in the Proceedings of the National Academy of Sciences, show how flexible human brains can be when learning new motor skills. A deeper understanding of how the brain generates movements could help illuminate what happens when that process goes awry, such as after a stroke.

Even before birth, babies tend to move one hand more than the other, an early sign of whether a person will be left- or right-handed. This preference probably comes from a mix of genetics and quirks of brain development. But this origin story isn’t what interested researchers. Instead, they wondered why a person’s dominant side — left or right — is more talented.

It could be that one half of the brain is just better at controlling movement. Or, as neurologist and neuroscientist Ahmet Arac now suspects, it could all come down to practice.

To tease these two ideas apart, Arac and his colleagues had 11 people write the letter A and the number 8 with either their dominant or nondominant hand. The results were exactly what you’d expect; dominant hands wrote the figures better.

Then, Arac, of the David Geffen School of Medicine at UCLA, and his colleagues threw these folks a curveball by asking them to write with a pen taped to an elbow. Half the people wrote with their dominant elbow, and the other half wrote with their nondominant elbow. Neither elbow — dominant or nondominant — was very good.

https://nautil.us/can-a-preteens-reaction-to-a-face-predict-their-future-social-lives-1282693

Can a Preteen’s Reaction to a Face Predict Their Future Social Lives?

By Jake Currie

Humans are social animals, so seeing a fellow human face triggers a cascade of activity in our brains. Information about the age, gender, familiarity, emotional state, and more get processed within milliseconds. Now, new research published in the journal Developmental Cognitive Neuroscience suggests how our brains respond to faces in our youth could impact our social lives later on.

“Faces contain a lot of social information, and perceptually or cognitively humans process that information really, really quickly,” study author Myles N. Arrington said in a statement. “That makes it great for neuroscience, because as soon as you show a face to a person it doesn’t take long for their brain to respond.”

Arrington and his fellow neuroscientists at the University of California, Davis studied brain activity of almost 6,000 children between the ages of 8 and 11 from the Adolescent Brain Cognitive Development Study. The kids were shown pictures of faces displaying positive, negative, and neutral emotions (which contain loads of social information) and places (which contain none) while their brain activity was monitored on an fMRI machine.

Combining the fMRI results with two-year follow-ups, they found that increased activity in the amygdala—the brain’s fight-or-flight center—in response to faces was correlated with changes in their social lives. Interestingly, boys and girls with heightened amygdala activity had much different results later in life. Girls with more active amygdalas tended to have more involvement with peers two years down the road, while boys showed less involvement.

According to the researchers, this could be due to differences in how the two genders are socialized. For example, “boys may be socialized to withhold intimacy and distance themselves from their peers,” the team wrote. It’s possible that this socialization can impact how their developing young minds process the social information contained in faces.

--------------------

https://www.sciencenews.org/article/new-alzheimers-drug-tau-promise

A new sort of Alzheimer’s drug shows glimmers of promise

By RJ Mackenzie

LONDON — An experimental drug can sweep tangles of tau from the brain, raising hopes that the treatment could help Alzheimer’s disease patients, according to clinical trial data released July 14.

The compound, called diranersen and developed by pharma giant Biogen, reduced tau levels in patients’ cerebrospinal fluid by between 50 and 65 percent as compared with the start of the trial. The drug also seemed to slightly slow people people’s cognitive decline compared with those given a placebo.

But it’s unclear whether a change of this size will help patients. And the results raised a puzzling conundrum: Contrary to expectations, the patients who had the biggest reductions in their levels of tau didn’t benefit the most in cognitive testing.

“This story has been almost a decade in the telling,” said neurologist Catherine Mummery, who presented data on the drug to a packed conference room at the Alzheimer’s Association International Conference. Mummery, head of novel therapeutics at the University College London Dementia Research Center, began the first diranersen trial in October 2017.

The results are a “significant step forward,” says molecular neuroscientist Heather Snyder of the Chicago-based Alzheimer’s Association. Over seven million people ages 65 and older in the United States have Alzheimer’s, and treatments to slow its progression, much less cure it, have been hard to come by.

Diranersen is what’s called an antisense oligonucleotide — a synthetic chunk of DNA that silences genes. It binds to the MAPT gene, which produces tau, a protein that’s been implicated in Alzheimer’s disease. In the condition, tau goes haywire, forming into tangles which damage nerve cells.

https://www.nytimes.com/2026/07/08/well/mind/omega-3s-supplements-benefits-brain.html?searchResultPosition=1

Are Omega-3 Supplements Actually Good for Your Brain?

By Dana G. Smith

In theory, taking an omega-3, or fish oil, supplement makes a lot of sense.

Omega-3 fatty acids are vital for brain health: They are used to build brain cells, keeping the cell walls flexible and enabling the neurons to sprout new connections and communicate with other cells. Numerous studies have shown that people with higher levels of omega-3s in their blood have better cognition and healthier looking brains, as well as a lower risk of developing dementia. In contrast, people with Alzheimer’s disease have been shown to have lower omega-3 levels.

But there’s a catch: The vast majority of clinical trials have found that taking omega-3 supplements offers virtually no benefit for cognition or dementia symptoms.

“It kind of intuitively makes sense” that neurons need fatty acids for their health, so you should take a fatty acid supplement, said Dr. Kristine Yaffe, a professor of psychiatry, neurology and epidemiology at the University of California, San Francisco. “The problem is that most of the evidence, particularly the trial evidence, just doesn’t support it at all,” she said.

A study published last month offers a prime example. The scientists who ran the clinical trial tried to cover all their bases: The participants were older adults who didn’t eat a lot of fish (which is rich in omega-3s), suggesting they might benefit the most from a supplement. Roughly half of the participants had an increased genetic risk for Alzheimer’s, which is another group that experts think might need more omega-3s. The researchers even did lumbar punctures on some of the participants to confirm that the supplement caused omega-3 levels in the brain to go up.

But compared with a placebo, the supplement didn’t result in any benefit when it came to people’s cognition or brain structure.

So what’s behind the disconnect? Scientists have a few hypotheses, and most are connected to diet and lifestyle.