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How should we study sex differences in a polarized age?

A new study on brain differences between sexes sparks a persistent question.

Photo: Ink Drop / Shutterstock
  • A new study found brain volume differences between men and women.
  • The research focuses on regional grey matter volume, a contentious measurement in neuroscience.
  • Without environmental conditions being considered, how trustworthy is our emphasis on biology?

In his book, "Chemically Imbalanced," University of Virginia research professor, Joseph E. Davis, questions the 20th century paradigm shift that created the belief that the brain is the last scientific frontier in understanding ourselves and the world. Neuroscience is valuable—that isn't in dispute. An expectancy that this discipline alone holds the keys to enlightenment is what's under debate.

Davis warns of the dangers of using biological explanations for social and personal dilemmas—namely, suffering. The entire field of psychiatry has fallen (or rather, been pushed) under the spell of brain chemistry, as I've repeatedly written about. Davis writes,

"Many of the claims about the relation of mind and mental states to brain are not really scientific at all and cannot themselves be tested in any empirical way. They rest no so much on a theory as on changed assumptions about human being."

This doesn't mean we should abandon the relationship of our brains to our bodies. We just can't confuse correlation with causation. In some ways, we've been sheltering in place for two centuries, thanks to indoor climate control and electricity. This "control of nature" has caused researchers to overlook the importance of the environment on mental health.

What about actual genetic differences in brain composition, however? Are they dependent on environment? This brings us to one of the more contentious debates in biology: genetic differences between men and women. A new study, published in Proceedings of the National Academy of Sciences, is forcing us to again confront that question.

The basis of the study is sound. Armin Raznahan, Chief of the Section on Developmental Neurogenomics at the National Institute of Mental Health, has been studying sex differences since he was a PhD student. He knows the field is filled with landmines. His first study was cited in an argument for same-sex schooling, which served as a wake-up call about the dangers of publishing on the subject.

Men vs. women: Why we’re imagining equality all wrong | Heather Heying | Big Think

This new research not only found sex differences in terms of regional grey matter volume (GMV), but also tied those differences to sex chromosomes. Specifically, after discovering neuroanatomical sex differences, the team found "that sex differences in regional GMV are aligned with functional systems for face processing."

This sparked the question of the validity of using grey matter to measure social and physical functioning, as this deep dive in Wired details. Raznahan's research found larger volumes of grey matter in men than women, though previous research has found women are better than men at facial recognition.

Grey matter is often used as evidence of stronger neurological connections. The default example is the famous London taxi driver study, which found that drivers, who have to memorize the entirety of the city to pass a rigorous test, have larger GMV in the brain's posterior hippocampi (spatial memory and navigation) than non-taxi drivers. This line of argument has also been used by meditation researchers, who have extrapolated from GMV volume to argue that meditation helps increase memory and empathy while decreasing stress.

Back to correlation and causation. Taxi drivers must study street maps for years; mediation is a specific discipline that has measurable effects on the nervous system (beyond grey matter). In both cases, the subjects have changed their relationship to their environment, thus hinting at correlation. If anything, you can argue environmental changes cause changes in GMV.

Raznahan's study is looking at genetic differences, yet environment still plays a role. The data was pulled from the U.S. and UK, predominantly white, wealthy countries. Comparing that data to other sets in African or Asian countries, for example, could result in a Bell Curve-type controversy—gender studies are already controversial enough. How then do you study biology when everything is polarized?

people at International Women's Day rally

Dozens of women and men attend a rally and march in Washington Square Park for International Women's Day on March 8, 2018 in New York City.

Photo by Spencer Platt/Getty Images

One political party in America grows angry any time a connection between income disparity and ethnicity is made. We seem unable to move beyond this political wedge, especially since it fires up the base, yet it holds the key to freeing scientists to take a holistic approach. You can't only look at changes in brain function when contemplating social differences. But you can investigate such differences if you're trying to understand brain disorders—the focus of Raznahan's work.

The gender question might always be with us. In 2014, Fallon Fox, a transgender MMA fighter, broke Tamikka Brents's skull during a match. Brents later said she had "never felt the strength that I felt in a fight as I did that night." There are real biological differences between men and women. Arguing against that is antithetical to good science.

Neuroscience will remain a sticky topic for some time, however. The methods for measuring blood flow and brain volume are, as Davis suggests above, more art than science. Until better measuring sticks are developed for understanding brain functionality, the field will be more speculative than declarative. That's okay: scientists need to fail in order to grow. In a time when even minor failures result in ostracism, however, that's a tough line to walk.

Environment always matters. Humans are the products of the spaces they inhabit. Genetic disorders aside, our chemistry is linked to our environment. When neuroscience is able to utilize brain scans in conjunction with sociology, real progress will be possible. Until then, controversies will abound, even where they should be none.


Stay in touch with Derek on Twitter, Facebook and Substack. His next book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."

Hulu's original movie "Palm Springs" is the comedy we needed this summer

Andy Samberg and Cristin Milioti get stuck in an infinite wedding time loop.

  • Two wedding guests discover they're trapped in an infinite time loop, waking up in Palm Springs over and over and over.
  • As the reality of their situation sets in, Nyles and Sarah decide to enjoy the repetitive awakenings.
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Two MIT students just solved Richard Feynman’s famed physics puzzle

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Our ‘little brain’ turns out to be pretty big

The multifaceted cerebellum is large — it's just tightly folded.

Image source: Sereno, et al
Mind & Brain
  • A powerful MRI combined with modeling software results in a totally new view of the human cerebellum.
  • The so-called 'little brain' is nearly 80% the size of the cerebral cortex when it's unfolded.
  • This part of the brain is associated with a lot of things, and a new virtual map is suitably chaotic and complex.

Just under our brain's cortex and close to our brain stem sits the cerebellum, also known as the "little brain." It's an organ many animals have, and we're still learning what it does in humans. It's long been thought to be involved in sensory input and motor control, but recent studies suggests it also plays a role in a lot of other things, including emotion, thought, and pain. After all, about half of the brain's neurons reside there. But it's so small. Except it's not, according to a new study from San Diego State University (SDSU) published in PNAS (Proceedings of the National Academy of Sciences).

A neural crêpe

A new imaging study led by psychology professor and cognitive neuroscientist Martin Sereno of the SDSU MRI Imaging Center reveals that the cerebellum is actually an intricately folded organ that has a surface area equal in size to 78 percent of the cerebral cortex. Sereno, a pioneer in MRI brain imaging, collaborated with other experts from the U.K., Canada, and the Netherlands.

So what does it look like? Unfolded, the cerebellum is reminiscent of a crêpe, according to Sereno, about four inches wide and three feet long.

The team didn't physically unfold a cerebellum in their research. Instead, they worked with brain scans from a 9.4 Tesla MRI machine, and virtually unfolded and mapped the organ. Custom software was developed for the project, based on the open-source FreeSurfer app developed by Sereno and others. Their model allowed the scientists to unpack the virtual cerebellum down to each individual fold, or "folia."

Study's cross-sections of a folded cerebellum

Image source: Sereno, et al.

A complicated map

Sereno tells SDSU NewsCenter that "Until now we only had crude models of what it looked like. We now have a complete map or surface representation of the cerebellum, much like cities, counties, and states."

That map is a bit surprising, too, in that regions associated with different functions are scattered across the organ in peculiar ways, unlike the cortex where it's all pretty orderly. "You get a little chunk of the lip, next to a chunk of the shoulder or face, like jumbled puzzle pieces," says Sereno. This may have to do with the fact that when the cerebellum is folded, its elements line up differently than they do when the organ is unfolded.

It seems the folded structure of the cerebellum is a configuration that facilitates access to information coming from places all over the body. Sereno says, "Now that we have the first high resolution base map of the human cerebellum, there are many possibilities for researchers to start filling in what is certain to be a complex quilt of inputs, from many different parts of the cerebral cortex in more detail than ever before."

This makes sense if the cerebellum is involved in highly complex, advanced cognitive functions, such as handling language or performing abstract reasoning as scientists suspect. "When you think of the cognition required to write a scientific paper or explain a concept," says Sereno, "you have to pull in information from many different sources. And that's just how the cerebellum is set up."

Bigger and bigger

The study also suggests that the large size of their virtual human cerebellum is likely to be related to the sheer number of tasks with which the organ is involved in the complex human brain. The macaque cerebellum that the team analyzed, for example, amounts to just 30 percent the size of the animal's cortex.

"The fact that [the cerebellum] has such a large surface area speaks to the evolution of distinctively human behaviors and cognition," says Sereno. "It has expanded so much that the folding patterns are very complex."

As the study says, "Rather than coordinating sensory signals to execute expert physical movements, parts of the cerebellum may have been extended in humans to help coordinate fictive 'conceptual movements,' such as rapidly mentally rearranging a movement plan — or, in the fullness of time, perhaps even a mathematical equation."

Sereno concludes, "The 'little brain' is quite the jack of all trades. Mapping the cerebellum will be an interesting new frontier for the next decade."

Economists show how welfare programs can turn a "profit"

What happens if we consider welfare programs as investments?

A homeless man faces Wall Street

Spencer Platt/Getty Images
Politics & Current Affairs
  • A recently published study suggests that some welfare programs more than pay for themselves.
  • It is one of the first major reviews of welfare programs to measure so many by a single metric.
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