While researchers have long known that sleep is an important part of maintaining our overall health and mental health, they haven’t always known exactly how this happened.
But in an amazing new study published recently in Science, two researchers now have a better understanding of the process of how sleep helps memory forms.
At least in mice (for now).
We are still at the early stages of really understanding the inner workings of the brain. Most of our research is still based upon examining how other mammal’s brains function using various testing procedures. Or understanding the effects of sleep deprivation — what happens when we don’t get enough sleep — on learning and memory.
The brain is made up of neurons that are interconnected. These connections are referred to as synapses. Scientists know that the strength of synapses are important for memories and learning, but have found paradoxical results when it comes to sleep. Previous research had suggested that sleep strengthens learning, but actually weakens synapses.
So Yang et al. (2014) set to explore these issues further and help us resolve the paradox.
Researchers have created ways of seeing into the brain directly to understand what activity is taking place, and where. We commonly think of techniques like fMRIs or PET scans. But researchers studying neuron activity have also come up with other innovative methods.
One of those methods is cutting a small area of a mouse’s skull away, to allow for microscopic imaging of the brain — and the synapse activity inside. All the while the mouse is still alive, and performing activities.
The researchers found that sleeping mice formed more synapses — the connections between neurons. This also enhanced their learning abilities.
By disrupting specific phases of sleep, the scientists also showed deep sleep (also referred to as slow-wave sleep) was necessary for memory formation. During this stage of sleep, it appears that the brain was replaying the activity from earlier in the day. The researchers believed this was an important component for enhancing and storing memories.
In summary, the researchers found that, like learning a new skill, the memory for places and events (e.g., “episodic memory”) is strengthened in these kinds of important ways during sleep. Keep in mind, though, that these are the findings of how neurons work in mice brains. Human brains are more complex, but the same basic principles may apply.
So next time you don’t think sleep matters all that much before a big day — whether it’s an exam, a presentation, whatever — think again. Sleep helps your memory and your learning skills. It’s the one thing you can easily stock up on when in doubt.
Yang et al. (2014). Sleep promotes branch-specific formation of dendritic spines after learning. Science, 344, 1173-1178. DOI: 10.1126/science.1249098