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There Is No Difference Between Male and Female Brains, Study Finds

Colors indicate the volumes of brain regions: green indicates large, and yellow indicates small. Image credit: Courtesy of Zohar Berman and Daphna Joel

A new study dispels the myths that there’s anything fundamentally different about men's and women’s brains. In fact, most people have some sort of mix of brain features typically categorized as “male” or “female,” researchers from Israel, Germany, and Switzerland found. 

The study, published in the journal PNAS, argues that if there were really such a thing as male and female brains, there wouldn’t be much overlap in the characteristics of the two—people would show either only male or only female characteristics. However, after examining the brains of 1400 people aged 13 to 85 years old in terms of their composition of gray matter, white matter, and connections, the researchers found that very few people were clustered on the extreme ends of the spectrum of features typically associated with males and females. Rather, there was a lot of overlap. While some features were more common in female brains and others in males, most people have a mix of the two. 

The science of sex differences in the brain is complicated, and hotly debated. Previous studies have indicated that men and women might have different proportions of white and gray matter in their brains or differences in how regions of their brains are connected. One study published in 2014 claimed these differences in functional connectivity underlie superior performance on spatial tasks in men and emotional recognition skills in women. Others argue that these differences are minuscule at best, and many studies subtly reinforce gender stereotypes through poor design, like not taking into account the varied experiences of the men and women tested, such as whether different hobbies or education might underlie their performance on social cognition or spatial processing tasks. 

Our results demonstrate that regardless of the cause of observed sex/gender differences in brain and behavior (nature or nurture), human brains cannot be categorized into two distinct classes: male brain/female brain,” the current study’s authors write. “[W]e should shift from thinking of brains as falling into two classes, one typical of males and the other typical of females, to appreciating the variability of the human brain mosaic.” 

[h/t New Scientist]

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Scientists Identify Cells in the Brain That Control Anxiety
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People plagued with the uncomfortable thoughts and sensations characteristic of anxiety disorders may have a small group of cells in the brain to blame, according to a new study. As NPR reports, a team of researchers has identified a class of brain cells that regulates anxiety levels in mice.

The paper, published in the journal Neuron, is based on experiments conducted on a group of lab mice. As is the case with human brains, the hippocampus in mouse brains is associated with fear and anxiety. But until now, researchers didn't know which neurons in the hippocampus were responsible for feelings of worry and impending danger.

To pinpoint the cells at work, scientists from Columbia University, the University of California, San Francisco, and other institutions placed mice in a maze with routes leading to open areas. Mice tend to feel anxious in spacious environments, so researchers monitored activity in the hippocampus when they entered these parts of the maze. What the researchers saw was a specialized group of cells lighting up when the mice entered spaces meant to provoke anxiety.

To test if anxiety was really the driving factor behind the response, they next used a technique called optogenetics to control these cells. When they lowered the cells' activity, the mice seemed to relax and wanted to explore the maze. But as they powered the cells back up, the mice grew scared and didn't venture too far from where they were.

Anxiety is an evolutionary mechanism everyone experiences from time to time, but for a growing portion of the population, anxiety levels are debilitating. Generalized anxiety disorder, social anxiety disorder, and panic disorder can stem from a combination of factors, but most experts agree that overactive brain chemistry plays a part. Previous studies have connected anxiety disorders to several parts of the brain, including the hippocampus, which governs memory as well as fear and worry.

By uncovering not just how the brain produces symptoms of anxiety but the individual cells behind them, scientists hope to get closer to a better treatment. There's more work to be done before that becomes a possibility. The anxiety cells in mice aren't necessarily a perfect indicator of which cells regulate anxiety in humans, and if a new treatment does eventually come from the discovery, it will be one of many options rather than a cure-all for every patient with the disorder.

[h/t NPR]

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Wilder Penfield: The Pioneering Brain Surgeon Who Operated on Conscious Patients
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Public Domain, Wikimedia Commons

For centuries, epilepsy was a source of mystery to scientists. Seizures were thought to be caused by everything from masturbation to demonic possession, and it wasn’t until the 1930s that a neurosurgeon showed the condition could sometimes be boiled down to specific spots in the brain. To do it, he had to open up patients’ heads and electrocute their brain tissue—while they were still conscious.

Wilder Penfield, the subject of today’s Google Doodle, was born on January 26, 1891 in Spokane, Washington. According to Vox, the Canadian-American doctor revolutionized the way we think about and treat epilepsy when he pioneered the Montreal Procedure. The operation required him to remove portions of the skulls of epilepsy sufferers to access their brains. He believed seizures were connected to small areas of brain tissue that were somehow damaged, and by removing the affected regions he could cure the epilepsy. His theory was based on the fact that people with epilepsy often experience “auras” before a seizure: vivid recollections of random scents, tastes, or thoughts.

To pinpoint the damaged brain tissue, he would have to locate the part of the brain tied to his patient’s aura. This meant that the patient would need to be awake to tell him when he struck upon the right sensation. Penfield stimulated the exposed brain tissue with an electrode, causing the patient to either feel numbness in certain limbs, experience certain smells, or recall certain memories depending on what part of the brain he touched. A local anesthetic reduced pain in the head; shocking the brain didn’t cause any pain because the organ doesn’t contain pain receptors.

During one of his surgeries, a patient famously cried, “I smell burnt toast!” That was the same scent that visited her before each seizure, and after Penfield removed the part of her brain associated with the sensation, her epilepsy went away.

Brain surgery isn’t a cure-all for every type of epilepsy, but treatments similar to the one Penfield developed are still used today. In some cases, as much as half of the brain is removed with positive results.

[h/t Vox]

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