Sleep. We all need it, yet for many Bowdoin students it can seem far from necessary. Lying there unconscious on an uncomfortable rectangular spring-loaded cushion hardly seems like the most productive use of your time. And from an evolutionary standpoint, what’s the survival advantage of spending more than a third of the day as an unconscious lump?
It seems absurd that an animal who lies down—unable to defend themselves for a significant amount of time every day—would rank higher in Darwinian fitness than one that didn’t. But sleep is ubiquitous throughout the animal kingdom. Even marine mammals who must surface to breathe will sleep, albeit one brain hemisphere at a time. Sleep’s ubiquity suggests that something productive must happen during our nightly paralysis.
The necessity of sleep becomes more clear after an all-nighter. Things start to feel crazy after the insane caffeine rush and the hopeless existentialism sets in around 3 a.m., followed by the grandiose euphoria realizing you might have actually written a decent paper shortly after sunrise. Aside from emotional instability, you may notice difficulty remembering how you spent the last five hours or what building you just came from.
For almost a century now, scientists have known that sleep is vital to memory—after a night’s rest it’s much easier to recall things learned earlier that day than if the night was spent cramming. Although this may seem obvious, it’s not exactly clear why this occurs and what about sleep actually assists memory formation. To address this question, it’s important understand what memories are and how they are formed.
The ability to form memories is possible due to neural plasticity, a term that sounds complex, but really just refers to the capacity of neural pathways to change due to chemical and electrical signals. The plasticity of the brain helps strengthen old synapses and form new ones. The repeated stimulation of these synapses can enhance your synaptic connections and memories are thought to result from this strengthening.
A recent University of Wisconsin-Madison study suggests that sleep enables neural plasticity and memory formation by weakening all connections in the brain to restore it to so-called “synaptic homeostasis.” Somehow, unimportant connections are weakened while crucial ones are spared.
Although initially controversial in the neuroscience community, this synaptic homeostasis hypothesis is gaining steam because of increasing supporting evidence.
For example, the number of dendrites—structures on each neuron that neighboring neurons connect to—decreases after sleep and increases once a person wakes. In addition, molecules that detect synaptic strength are more prevalent in synapses during the day and also decrease after a night’s rest. These two phenomena are leading to a completely different idea of how sleep shapes memory.
This homeostasis hypothesis explains other important anomalies in sleep science. Your brain uses more energy as it is stimulated, so if it wasn’t able to recover, it would use an unsustainable amount of energy. If the brain restores neural balance and weakens synaptic connections through sleep, the brain would be much more efficient in the long run.
Now when you reach for that triple shot espresso from the Café to continue working long throughout the night, remember that sleep helps restore your neural balance and allows your brain to function much more efficiently. The productivity of your all-nighter will likely be lost in the delirium and confusion of the next day.
Help your brain get back to its baseline and go take a nap.