In some ways it’s a mystery why exercise is so good for the brain.
That’s because exercise is stressful and stress is, broadly speaking, bad for the brain.
Nevertheless exercise produces a host of benefits, it:
- enhancing structural plasticity,
- reduces anxiety,
- improves learning and memory function,
- increases blood flow to the brain…and all the rest…
But perhaps there’s something special about stressful, but rewarding activities, like exercise or, say, sex?
It’s this connection between sex and brain function that’s been investigated in a series of intriguing studies.
In one, conducted at Princeton University, young adults rats were either allowed to have sex only once in a two-week period, or every day (Leuner et al., 2010).
What they found was that sex was stressful–the rats had elevated levels of stress hormones–but sex also promoted brain cell growth.
The rats that had been having sex for two weeks displayed neurogenesis: the process by which neurons are generated from stem cells in the brain.
The neurogenesis was found in part of the hippocampus, a structure that is thought to contribute to memory formation and other important cognitive functions.
The more sexually active rats also displayed less anxiety.
Middle aged rats
All very well for the younger rat, you might say, but what about the poor, downtrodden middle-aged rat?
He’s losing his looks, his fur and…well…he’s a rat.
When the same research group carried out a similar experiment on older rats, they reached the same conclusions (Glasper & Gould, 2013).
If older rats continued to have sex, neurogenesis in the hippocampus was enhanced.
So there’s hope for the older rats amongst us as well.
The effect did not, however, persist after the rats stopped having sex: they had to keep at it.
Improved memory and learning
Researchers at Princeton are not the only ones to be examining the link between sex and neurogenesis.
In South Korea they’ve been carrying out similar experiments on mice, except they’ve taken them one step further.
If the hippocampus is involved in memory and learning, and sex makes cells there grow, then surely sex should improve memory and learning?
To test this out, Kim et al. (2013) had some male mice locked up with horny females while others sat like monks in their cells.
Once again, sex proved beneficial for the hippocampus. But the mice were also given tests of their memory and learning ability.
The results of this showed that mice that had been having sex aced the task in comparison to their monkish counterparts.
Sex and the brain
Perhaps these studies start to explain why stressful activities like exercise are also so good for the brain, despite being stressful: they encourage the growth of new brain cells.
So, not all stress is bad stress: the right kind can do wonders–even for the older rat.
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Image credit: Hannah Kate