The human brain plays new memories at 20 times the speed during wakefulness

According to a study published June 8 in the journal Cell Reports, neural playback during wakefulness may help consolidate memory of sequences of action in humans. The brain imaging results showed rapid, repetitive reactivation of a neural network, which is a sequence of behavior that people learned – about 20 times as fast as the new memory – especially during breaks in exercise.

This is the first demonstration of the awake neural rendering of a newly learned skill evoked by practice in humans. This study is also the first to show that wakeful replay predicts a rapid consolidation of the skills responsible for early learning.

Senior study author Leonardo G. Cohen of the National Institute of Neurological Disorders and Stroke (NINDS), which is part of the US National Institutes of Health.

It is possible that wakefulness repetition through offline recapitulation of previous practices promotes the vigilant consolidation of skills – a problem that has not been explored in either human or animal models.

First author Ethan R. Book of NINDS.

To test this idea, the researchers used a brain imaging technique called magnetic encephalography (MEG). MEG data showed that a neural reproduction of the keystroke sequence occurred during rest periods when awake.

The neural rendering took only 50 milliseconds – 20 times faster than the actual behavior. These repetitive events were approximately three times more frequent during the rest periods between workouts compared to the rest periods before or after exercise. In addition, the repetition frequency during the first 11 attempts, when the subjects learned faster, was higher compared to the last 11 attempts. In addition, greater skill consolidation was associated with more repetitive events during the rest breaks between exercise periods.

Neural replay recruited a brain network that included hippocampal, sensorimotor, and entorhinal regions.

The strong involvement of the hippocampal and medio-temporal activity in reproducing procedural motor memory was surprising, since this type of memory is often viewed as unnecessary for the hippocampus to need contributions. In summary, our data show that frequent, rapid repetitions while awake reinforces the hippocampus and neocortical associations learned during the previous exercise – a process relevant to improving subsequent performance and consolidating wakefulness skills.

Ethan R. Book

Going forward, researchers plan to use non-invasive brain stimulation to test whether repetitive waking plays a causal role in early skill learning and to see whether rapid consolidation supports other types of memory.

Ultimately, understanding the characteristics of repetitive waking that are important for skill learning could lead to optimizing therapy plans or identifying better brain stimulation strategies aimed at improving rehabilitation outcomes after brain lesions such as stroke.

Leonardo G. Cohen

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