The daily decline in hormones in a man’s body may play a role in shrinking the brain throughout the day, a study suggests. After losing sound between morning and evening, the brain resets at night, starting the cycle again, research shows.
The study involved scanning the brains of a 26-year-old man 40 times over 30 days. Each magnetic resonance imaging (MRI) scan was collected at 7 am or 8 pm, which is when levels of steroid hormones – namely, testosterone, cortisol and estradiol – are at their highest and lowest, respectively.
“Men show this 70% reduction from morning to night in steroid hormones,” said a co-author of the study. Laura Pritschetwho is now a postdoctoral fellow in the department of psychiatry at the University of Pennsylvania Perelman School of Medicine. The degree of change between morning and night decreases with age, but that general pattern continues throughout life.
“You can think of it as a rhythm that beats from morning to night,” Pritschet told Live Science. Women also experience a daily flow of hormones, but it is not as pronounced as it is called, he noted, because menstrual cycle at the same time it facilitates long-term hormonal changes.
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A new study has revealed that, over the course of the day, the overall volume of the human brain decreases, as does the thickness of the cortex, the outer layer of the brain. The volume of gray matter, which contains nerve cells and the connections between them, decreased by an average of 0.6%.
Two parts of the cortex, known as the occipital and parietal cortices, are the most reduced. Changes were also seen in deep brain structures, including the cerebellum, brainstem and brain regions hippocampus. These parts of the brain are respectively involved in coordinating movement; transmitting information between the brain and the body; and saving memories.
A decrease in brain volume is accompanied by a daily drop in hormones. However, it is not yet clear whether hormones drive brain changes, the study authors wrote in a report published Wednesday (Sept. 18) in Journal of Neuroscience.
I like the counterpoint that we are now highlighting the ways in which the male endocrine systems are changing.
Pavel Shapturenka, the subject of the study
“I think it’s an open question,” study co-author Elle Muratadoctoral student in psychology and brain science at the University of California, Santa Barbara (UCSB), told Live Science. But still, “this is, I think, another example that dispels the myth that hormones only work for women.”
Previous research shows that steroid hormones shape the brain. The Menstruation is associated with changes in volume throughout the brain, and studies show when those changes do not occur the hormonal cycle changes – for example, with birth control. Decades of animal studies it also suggests that steroid hormones shape the brain in short periods of time.
“I’m convinced that hormones affect the brain and brain structure,” Murata said. “But in this study, we can’t say it’s the direct cause.”
It could be male hormones circadian rhythm does it affect brain function? At present, it is unclear how it can do so. That said, a separate group study suggests that there are changes in brain connectivity that follow the 24-hour cycle.
In that other studythe group examined the same person but looked at communication patterns between different parts of the brain, rather than taking pictures of their structure. The researchers found that “coherence” – a measure of coherence – across the brain rose and fell along with steroid hormone levels.
Interestingly, the areas of the brain that process visual information were activated in both studies, Murata noted. These brain regions showed both loss of volume and loss of coherence throughout the day.
“Maybe there’s something going on in the visual network,” Murata suggested. “The jury is out on why this might be.” It is also important to note that this pattern was observed in the brain of one person, and different patterns may appear in different people.
Topic of current studies, Pavel Shapturenkatold Live Science that he found the brain scan “relaxing,” almost hypnotic. When asked why he volunteered to do research, he said it was a “unique opportunity” to contribute to an area of neuroscience that we don’t know much about. (Shapturenka and Pritschet are married and both were medical students at UCSB at the time of data collection, although Shapturenka studied chemical engineering rather than brain science.)
“All the data out there highlights the natural endocrine system [hormonal] female differences,” said Shapturenka. “I like the counterpoint that we are now highlighting the ways in which the male endocrine system is changing,” especially since that difference may affect brain function, she said. he said.
Pritschet and Murata said that the next step could be to investigate how differences in sleep alter this brain power. Sleep disturbances are tied to metabolic diseases and mental health conditionsso it would be interesting to see how the daily brain cycle fits into that picture. Getting rid of brain waste – it is called the “glymphatic system”. – also comes online during sleep and therefore may have a role to play in this daily cycle, they said.
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