Sunday 10 March 2024

Differences in brain gray matter thickness between women and men due to inequality

A study published in May 2023 makes what I think is a remarkable finding but perhaps it isn't remarkable. Perhaps it is predictable. The study came to the conclusion that where there is gender inequality between men and women and specifically where women are treated unequally and granted lesser human rights and freedoms, they can have thinner brain cortices than men. This only happens in a country where there is gender inequality.

Differences in brain gray matter thickness between women and men due to inequality
Image: MikeB under license.


Note: you might just want to read the first paragraph of this section and then skip through to the next section. It's here to explain what part of the brain is affected by gender inequality as stated by this study.

For the sake of clarity: The cortices, or cerebral cortices, are the outermost layer of the brain, often referred to as the "gray matter." They are highly folded and convoluted to increase the surface area within the limited space of the skull. The cerebral cortex plays a crucial role in many complex cognitive functions, such as perception, attention, memory, language, decision-making, and motor control.

The cerebral cortex is divided into two hemispheres, the left and right, which are connected by a bundle of nerve fibers called the corpus callosum. Each hemisphere is further divided into four lobes: the frontal lobe, parietal lobe, temporal lobe, and occipital lobe.

The frontal lobe is involved in executive functions, decision-making, planning, and motor control. It also plays a role in personality and higher-order cognitive processes.

The parietal lobe is responsible for processing sensory information, including touch, temperature, pain, and spatial awareness. It plays a role in spatial perception, attention, and object manipulation.

The temporal lobe is involved in auditory processing, language comprehension, memory formation, and the interpretation of sensory input.

The occipital lobe is primarily responsible for visual processing and interpreting visual stimuli from the eyes.

Each of these lobes contains specialized regions known as cortical areas or regions that are responsible for specific functions. These areas often work together in complex networks to support various cognitive processes. The precise functions and interactions of different cortical areas are still an active area of research in neuroscience.

Mental Health

The study also found that gender inequality is linked to worse mental health and academic achievement in women. The latter is going to be linked to the above i.e. the thinner grey matter (cortices).

The study looked at a dataset of almost 8000 MRI scans from healthy adults living in 29 different countries. They came to the conclusion that "gender inequality is associated with differences between the brains of men and women: cortical thickness of the right hemisphere, especially in limbic regions such as the right caudal anterior cingulate and right medial orbitofrontal, as well as the left lateral occipital, present thinner cortices in women compared to men only in gender-unequal countries."

It is very technical but the way I understand it is that the grey matter of the brain is smaller, thinner; there is less of it, and it could be argued  - as one news media outlets says - that the brain shrinks.

Stress (and under-exercised?)

My thought about this for what it is worth is that if a brain is not exercised because it has not have the opportunity to be exercised because a woman is kept in a subservient role, it will possibly shrink and be smaller than that of a man's brain. It's about exercising the brain as one exercises muscles and the entire body. The scientist, however came to a different conclusion name is that stress is the cause of brain shrinkage (see below).

Gender-unequal countries

The study was based at Oxford University. Countries where there is the greatest inequality are, for example, India, Turkey and Brazil. The study concluded that the thickness of the grey matter of the right hemisphere of women's brains was between 3-5% thinner than men's in these countries.

Gender-equal countries

In countries where there is minimal inequality such as the Scandinavian countries, Sweden and Finland, there is no significant difference between the sexes in terms of grey matter thickness.

In the UK there is a slight difference which is surprising. They found that there is a 0.5% thinning in the right hemisphere of the brains of women which has been attributed to gender inequality in the UK.

Stress is the cause

The researchers think that the difference is due to the effect of "chronic stress in women's brains in gender-unequal environments. Stress affects neurons' connections. This "we would then see as thinning of the gray matter cortex in MRI studies".


P.S. please forgive the occasional typo. These articles are written at breakneck speed using Dragon Dictate. I have to prepare them in around 20 mins.

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