Study Reveals Human Brain Processes New Skills During Sleep

Conducted by researchers at Massachusetts General Hospital in collaboration with Brown University and other institutions, the findings were published in the Journal of Neuroscience on June 22, 2022. This study builds on previous animal research that identified a phenomenon known as "replay," where the brain seemingly practices newly learned information during sleep.

Dr. Daniel Rubin, a neurologist at the MGH Center for Neurotechnology and Neurorecovery and lead author of the study, noted that when trained laboratory animals, such as mice, navigate mazes, specific neurons activate. During sleep, those same neurons can reactivate in sequence, suggesting that the brain replays experiences to help consolidate memories.

"There’s been an open question in the neuroscience community: To what extent is this model for how we learn true in humans?" asked Dr. Sydney S. Cash, co-senior author of the study. Understanding this process in humans, particularly regarding motor skills, could inform the development of new therapies for neurologic diseases and injuries.

To investigate whether replay occurs in the human motor cortex, the researchers engaged a 36-year-old participant with tetraplegia, identified as T11, who is part of a clinical trial for a brain-computer interface. The device, being developed by BrainGate, allows T11 to control a computer cursor through thought.

During the study, T11 performed a memory task similar to the game Simon, where he recalled a sequence of flashing colored lights. Brain signals corresponding to his intended hand movements were recorded and transmitted wirelessly. Remarkably, while sleeping at home, T11's motor cortex displayed activity reflecting the same patterns of neuronal firing observed while he played the memory task.

Dr. Rubin highlighted that this represents the first direct evidence of neuronal replay from the motor cortex during sleep in humans. The majority of this replay was recorded during slow-wave sleep, with significantly less occurring during REM sleep. The findings provide a basis for further exploration of replay in human memory and learning.

Dr. Cash remarked on the significance of this research in advancing understanding of the brain's workings, while Dr. Leigh Hochberg emphasized the unique opportunity presented by the BrainGate participants to contribute to both practical applications and fundamental neuroscience.

The study received support from various institutions, including the U.S. Department of Veterans Affairs and the National Institutes of Health.