Study: How Electric Brain Simulation During Sleep Improve Memory

Scientists from the University of North Carolina's School of Medicine have devised a new non-invasive method to help strengthen the memory of millions of people suffering from Alzheimer's disease, schizophrenia and major depressive disorder.

For the new method, the researchers used transcranial alternating current stimulation, or tACS to target a specific kind of brain activity during sleep known as sleep spindles. Sleep spindles are the waves that appears on an electroencephalogram (EEG) that represent an electrical brain activity that oscillates or alternates during sleep.

Previously, scientists have suspected the involvement of sleep spindles in cataloging and storing memory during sleep, but they are uncertain if sleep spindles enable or even cause memories to be stored and consolidated.

"They could've been merely byproducts of other brain processes that enabled what we learn to be stored as a memory," commented senior author Flavio Frohlich, PhD, assistant professor of psychiatry and member of the UNC Neuroscience Center, in a statement.

However, a new study published in the journal Current Biology revealed that sleep spindles play a crucial role in the process in making memories. Furthermore, the study also showed that sleep spindle can be targeted to enhance memory.

For the study, the researchers recruited 16 male participants. The participants first underwent a screening night of sleep before completing two nights of sleep for the study. The participants were asked to perform associative word-pairing tests and motor sequence tapping tests. Electrodes were placed at a specific spots on the scalps of the participants.

During the first study night, each participant received an alternating current of weak electricity synchronized with the brain's natural sleep spindles. On the other hand, each participants received a shame simulation in the second night to serve as placebo.

The researchers ask the participants to perform the two standard memory tests. The researchers noted a significant improvement in the motor task tests of the participants in the simulation night when compared in the placebo night. However, the researchers did not observed any significant difference in the scores of the word-association tests.

"We're excited about this because we know sleep spindles, along with memory formation, are impaired in a number of disorders, such as schizophrenia and Alzheimer's. We hope that targeting these sleep spindles could be a new type of treatment for memory impairment and cognitive deficits," said Caroline Lustenberger, PhD, first author and postdoctoral fellow in the Frohlich lab, in a press release.

The researchers are now planning to try the same non-invasive interventions to patients with irregularities in their sleep spindle pattern to determine if the new treatment is effective in improving memories of patients with neurological conditions.