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Evidence That Human Brains Replay Our Waking Experiences While We Sleep

In This Article

  • Previous studies on "replay," in which the brain replays neural firing patterns during sleep, have only been conducted on animal brains
  • A new study provides direct evidence in two participants that offline replay is present in human brains as well
  • The study utilized implanted multi-electrode arrays to record the spiking activity of large groups of individual neurons in the brain

For the first time, researchers report direct evidence that the human brain replays waking experiences while asleep. This research, led by Sydney S. Cash, MD, PhD, associate in the Department of Neurology, and Leigh Hochberg, MD, PhD, director of the Center for Neurotechnology and Neurorecovery at Massachusetts General Hospital, was reported on May 5 in the journal Cell Reports.

The phenomenon known as "replay," in which, during sleep, the brain replays neural firing patterns experienced while awake, is thought to aid in memory consolidation. However, prior to this study, offline replay had only been observed in animals.

The researchers asked two participants to play a sequence-copying video game with their minds—imagining moving the cursor and hitting targets one by one. The participants then went back and forth between napping and playing the game, while researchers recorded the spiking activity of large groups of individual neurons in their brains through an implanted multi-electrode array.

The electrode arrays used in this study are the first small enough to allow for detailed neural recordings of the brain. When observing these neural recordings, investigators observed identical firing patterns during the gaming period and the post-game sleep period, providing direct evidence of learning-related replay in the brain.

Although there is more to uncover about the memory consolidation process, studies like these continue to show that sleep plays a vital role in learning and memory. Getting a good night's sleep before important life events is beneficial for good cognitive performance.

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