We spend around one-third of our life vulnerable, snoozing away the hours while prone to mosquito bites, bear attacks, and college pranks (depending on your lifestyle).
Confident that there’s a critical benefit to dropping into a regular state of unawareness, researchers will typically search for signs of repair and maintenance that occur within our bodies while we sleep.
One hypothesis suggests our brains enter a low-energy state each day to restore balance to the connections between neurons.
A recently published study led by researchers at the Jülich Research Centre in Germany has uncovered evidence of “synaptic down-selection” as we sleep, suggesting our nightly shut-eye is a perfect opportunity to prune back any neurological hedges that went wild during the day.
Known as the synaptic homeostasis hypothesis, it’s thought that being awake and engaging with the world strengthens the connections between brain cells, a process that chews up energy and strews metabolic litter throughout our brain’s gutters.
To clean up the mess and save energy, we need to cut back on these synaptic connections, something that can only be done while we aren’t actively constructing them.
Observed in animal studies, the synaptic homeostasis hypothesis has yet to be studied in humans.
Researchers behind this latest investigation used PET imaging to look for radioactive tags they’d attached to synaptic vesicle glycoprotein 2A (SV2A) in a group of living human volunteers.
These vesicles appear at the connections between neurons, providing researchers with a way to measure synapse density.
Half of a group of 40 volunteers were instructed to go without sleep for a single evening. After 28 hours of staying awake, their brains were scanned.
A comparison between the brains of those who went without sleep and those who had a good night’s rest revealed clear differences in the densities of their synapses, particularly in regions responsible for memory, integrating sensory information, and relaying information across the central nervous system.
Those with sleep-deprived brains were then permitted a two-hour nap, during which their brainwaves were scanned. Those with higher concentrations of SV2A were more likely to present slow-wave activity while they rested, a sign that their brains were slipping into a deeper, more restorative state of sleep.
While the scans couldn’t show exactly what was happening during sleep, it seems likely that higher densities of synapses are a trigger for non-dreaming states of sleep, during which these connections are whittled down to what is necessary for facing the world the following day.
This isn’t to say sleep only has a single benefit, or that we evolved sleep solely to do some neurological gardening. The findings do finally provide solid evidence that to get the most from our energy-hungry, complex brains, we need to find time to sleep each night.
Combined with evidence that a lack of sleep increases our odds of developing neurodegenerative disorders like Alzheimer’s disease, turning in early and sleeping soundly is probably the best thing we can do to keep ourselves mentally fighting fit.
This research was published in PLOS Biology.
Source: Institute of Neurosciences and Medicine via MedicalXpress
Fact-checked by Bronwyn Thompson
