A new study on sleep and learning shows a new development in brain activity at rest. Some of the neurons in the brain may be activated during sleep in a way that researchers believe may be the brain trying to predict the future.
New research from Rice University and the University of Michigan builds on existing studies showing that sleep is important for learning because it helps form new memories.
It is not clear whether the activity the researchers observed is actually responsible for dreaming. This would mean that some of our dreams are trying to predict the future. But I will say that I think I experienced this newfound feature of the brain when I was much younger.
I would routinely wake up during the night with solutions to some of the more challenging math problems for school. I would wake up and write. I would be so excited to find the correct answer. My brain was probably working overtime while I slept. I must have dreamed that I could solve a puzzle that seemed too difficult just a few hours earlier. This happened with video games later in life.
The Rice and Michigan scientists did not test their hypothesis in humans. Instead, they looked at the rats’ brains while they were awake and performing a specific task. They then followed the animals during sleep and observed how the neurons in the brain worked.
A machine learning algorithm allowed them to conclude that the rats were actually dreaming of a new place that they had just experienced while awake.
A report from Rice University explains that other studies observed decades ago that the brains of sleeping animals exploring a new environment just before falling asleep fired in ways that allowed them to replay the new trajectories. Thus, the brain could form new memories.
However, the researchers decided to determine whether neurons during sleep try to present the problem in a new light.
«We imagined that some neurons might change their representations ⎯ reflecting the experience we’ve all had of waking up with a new understanding of a problem,» said neuroscientist Caleb Kemere.
The researchers trained rats to run back and forth on an elevated track with liquid rewards at either end. They observed how individual neurons in the hippocampus would «jump». The scientists calculated the average firing rate of neurons over many circuits. So they estimated a neuron’s place field, «or the area in the environment that a particular neuron ‘cares about’ the most.»
The next step was to assess the place field behavior when the animals were sleeping. Therefore, they did not move through the labyrinth.
«We solved this challenge by linking the activity of each individual neuron to the activity of all the other neurons,» said Michigan anesthesiology associate professor Kamran Diba.
This is where artificial intelligence comes in. The researchers used machine learning algorithms to examine the neurons and determine where the animal dreamed it was. They then used fictional positions to assess the spatial tuning process for each neuron they observed.
So the researchers noticed that the neurons are not just trying to stabilize the new memory that the brain is forming. It is as if the animals relive the problem during sleep. Here’s how Kemere explained the findings in the Rice University report:
What I liked most about this research, and the reason I was so excited about it, was the discovery that it’s not necessarily the case that during sleep the only thing these neurons do is stabilize the memory of the experience. It turns out that some neurons end up doing something else.
We can see these other changes that occur during sleep, and when we return the animals to the environment a second time, we can confirm that these changes really reflect something that was learned while the animals were sleeping. It is as if the second exposure to space actually occurs while the animal is sleeping.
This may be the first study to show that neuroplasticity occurs during sleep. Plasticity research examines the mechanisms that allow neurons to rewire and form new representations. But most studies observe this activity while subjects are awake and dealing with stimuli.
What about nightmares and deja vu?
Forget solving math problems while I sleep. If these findings are correct, I would like to know what nightmares are when we look at neurons from this perspective. Maybe the brain is really trying to predict the worst outcome by making me have near-death adventures in my sleep.
Also, I can’t help but wonder if deja vu, the feeling of experiencing a certain event, is related to that specific brain behavior.
I’m guessing a lot, and it may take more researchers, perhaps on real human brains, to examine these questions. In the meantime, you’ll find a full brain sleep study Nature.