Scientists Now See How The Brain Records Memories During Sleep

Scientists have known for a long time that brains require sleep to review the events of the day and convert them into longer-term memories. The exact way on how the brain does this is, however, poorly understood. Now, for the first time, they have gained first-hand insight into just how the organ transforms and stores memories.

Memories And Sleep

Students are often advised to study before sleeping to help them recall what they reviewed for the test. While it may have been viewed in the past as old wives' tale, sleeping after studying may help after all. Researchers planted tiny microelectrodes inside the brains of two individuals to observe what the brain does while sleeping, what they saw astounded them.

The contraption allowed scientists to see how the neurons of the brain fire up during sleep as it “replays” short-term memories as it moves them into more permanent storage. Their study was published in the journal Cell Reports on Tuesday.

Dr. Richard Isaacson, a neurology specialist at Weill Cornell Medicine in New York, expressed a fascination for the study. “Despite decades of research, it remains somewhat unclear how 'short-term' memories get filed away to become 'long-term' memories that can be recalled later,” he said. Dr. Isaacson, who also directs the Alzheimer's Prevention Clinic at New York-Presbyterian Hospital, is not involved in the study.

Brain-Computer Interface

The study was performed at BrainGate, a consortium of academic research scientists from the Providence VA Medical Center, Stanford University, Brown University, Case Western Reserve University, and Massachusetts General Hospital.

The group spent over ten years developing brain-to-computer interfaces that help people who are unable to use their limbs due to injuries or diseases, use brain signals to command computers. They include patients who have neurologic diseases like amyotrophic lateral sclerosis (ALS), brain injury, and those who lost their limbs.

Using Electrodes To Observe Neurons

Surgeons at BrainGate implanted tiny electrodes on top of the brains of two individuals to observe the organ’s neurons. They were asked to play a sequence game where they are to repeat the order of movement. Instead of limbs, they used their minds to repeat the actions while electrodes record their neural activity. They were then asked to sleep while the electrodes recorded the activity of their neurons as a baseline.

The results showed that as the participants slept, movements of their neurons were found to correlate with activity recorded while playing the game. This meant that their brains continued playing the sequence game after sleeping, replaying the same patterns at the neuronal level.

According to Dr. Isaacson, completely understanding how memory gets stored in the brain can help unlock secrets to cognitive function. He expressed hope that future studies will also help explain which particular stage of sleep such memory replay happens most frequently.