REM sleep locks in skills and experiences
New research from Washington State University Spokane shows that rapid eye movement (REM) sleep actively converts waking experiences into lasting memories and abilities in young brains. The study, published in Science Advances, expands our understanding of children’s sleep needs and raises questions about the growing use of medications that can disrupt REM sleep, such as certain stimulants and antidepressants. The work was supported by the National Institutes of Health.
How REM makes experience “stick”
Marcos Frank, professor of medical sciences, notes that infant animals spend much of early life in REM sleep, but the mechanisms by which REM consolidates and reshapes memories were not well understood. Frank and his team investigated how sleep affects visual development in young animals and found that REM sleep is necessary to stabilize experience-driven changes in the visual cortex.
The researchers identified the enzyme ERK (extracellular signal–regulated kinase) as a key molecular switch: ERK becomes active only during REM sleep and is required to convert transient activity into lasting structural and functional changes. Without REM-triggered ERK activation, experience-dependent changes in the brain fade and do not persist.
“REM sleep acts like the chemical developer in old-fashioned photography,” Frank said, “making traces of experience more permanent and focused in the brain.” He emphasizes that waking experience alone is fragile unless consolidated during REM sleep.
REM sleep during critical developmental periods
During early life, brains undergo critical periods of heightened plasticity when sensory systems and higher cognitive functions—vision, speech, language, motor and social skills—are refined. The study suggests that REM sleep helps young brains adjust the strength and number of neuronal connections to match environmental input during these periods.
REM and vision: the experimental model
Historical clinical observations dating to the 1960s showed that delayed treatment of congenital cataracts in children can cause long-term visual problems such as double vision and eye misalignment. Building on that knowledge, the Washington State researchers used a monocular deprivation model to probe REM’s role in ocular dominance plasticity.
In the experiment, animals had one eye temporarily patched while their brain activity was recorded during wakefulness and sleep. Some animals were selectively deprived of REM sleep—woken gently during REM—while control animals were awakened during non-REM sleep. The outcome was clear: animals missing REM sleep failed to develop normal vision in the patched-eye model.
Without REM sleep, permanent plastic changes in the visual cortex did not occur, and ERK did not activate. Previous work from the team shows ERK activation leads to production of proteins that consolidate synaptic changes, making them long-lasting.
Brain activity during REM mirrors waking experience
Surprisingly, the team observed patterns of cortical activity during REM sleep that resembled activity seen while the animals were awake and experiencing the environment—a kind of neural “replay.” This replay coincided with times of maximal ERK activation, suggesting a direct link between reactivation of waking patterns in REM sleep and the molecular mechanisms that consolidate experience.
“It’s as if the neurons were dreaming of their waking experience,” Frank said. He noted this is among the first demonstrations of waking-like activity reappearing during REM in the developing brain, and it points to a role for REM beyond the visual system—potentially affecting other brain regions and processes across the lifespan.
Implications for children and clinical practice
Frank says the findings have significant implications for child development and pediatric healthcare. There is mounting evidence that the amount and quality of sleep influence academic performance and overall cognitive development. This study provides a mechanistic explanation for why sleep—especially REM sleep—matters during periods when the brain is rapidly changing.
He warns that many commonly prescribed medications for children, including stimulants for attention deficit disorders and some antidepressants, can suppress sleep and REM sleep in particular. REM is fragile and easily inhibited by drugs, yet there is limited preclinical data on how these compounds affect the developing brain short- and long-term. The new evidence argues for caution when prescribing REM-suppressing medications to young patients and highlights the importance of protecting healthy sleep during development.
Funding: Supported by the National Institutes of Health.
Source: Marcos Frank, Washington State University.
Original research: The study—“Rapid eye movement sleep promotes cortical plasticity in the developing brain”—was published in Science Advances (online July 3, 2015). The authors include Michelle C. Dumoulin Bridi, Sara J. Aton, Julie Seibt, Leslie Renouard, Tammi Coleman and Marcos G. Frank. The paper reports that preventing REM sleep after monocular deprivation reduced ocular dominance plasticity and inhibited activation of ERK, and that cortical activity during REM resembled the activity present during deprivation, corresponding to times of maximal ERK activation.
Abstract
Rapid eye movement sleep promotes cortical plasticity in the developing brain
REM sleep reaches its peak during early life, yet its functional role in the developing brain has been unclear. Using a canonical model of developmental plasticity (ocular dominance plasticity induced by monocular deprivation in cats), the researchers found that preventing REM sleep after sensory deprivation reduced ocular dominance plasticity and inhibited activation of extracellular signal–regulated kinase (ERK), a kinase critical for this form of plasticity. Chronic single-neuron recordings in freely behaving animals revealed that cortical activity during REM sleep resembled the activity present during monocular deprivation, and these REM-associated reactivations matched times of high ERK activation. Together, these results indicate that REM sleep promotes molecular and network adaptations that consolidate waking experience in the developing brain.