Imagine a time when you can enjoy the restorative benefits of sleep without actually falling asleep. Recent research involving awake mice has demonstrated that stimulating certain brain activities can mimic the benefits of deep sleep, including enhanced memory function.

“In theory, we might replicate these findings in humans,” says Vladislav Vyazovski from the University of Oxford, who was not part of the study. “Investigating the potential for artificially inducing this state during wakefulness could be fascinating.” This type of brain activity might lead to a feeling of refreshed energy while awake.

Sleep is crucial for the brain’s maintenance functions, such as synaptic homeostasis, which organizes the numerous neural connections formed throughout the day, reinforcing essential pathways while eliminating the unnecessary ones.

Non-rapid eye movement (NREM) sleep, which makes up about 80% of adult sleep, features repetitive signal firing from the brain’s cortex, shutting off certain neurons in a pattern known as slow-wave sleep activity. “This phenomenon is likely linked to synaptic homeostasis and may be key to sleep’s restorative capabilities,” explains Chiara Cirelli from the University of Wisconsin-Madison.

Cirelli and her team pondered whether it might be feasible to induce a section of the cerebral cortex into a deep sleep state while keeping a person awake. Certain animals like dolphins and fur seals utilize a similar tactic, allowing half of their brains to enter NREM sleep while remaining vigilant.

To explore this possibility, the researchers genetically altered mice to control neural activity using light. They inserted a probe into part of the mice’s brains and kept them engaged for five hours with various stimuli. At the end of this duration, a light probe was activated to simulate non-REM sleep for 30 minutes.

After putting the mice to sleep, brain recordings revealed that the stimulated region of the brain did not exhibit typical signs of fatigue associated with sleep deprivation. “Essentially, a portion of the brain cleansed itself while awake, minimizing the need for restorative deep sleep later,” says Cirelli.

The researchers then explored whether artificially induced sleep during wakefulness could enhance memory. They placed the genetically modified mice in a box with identical carpet textures on both sides. After allowing them to explore for 15 minutes, the mice were divided into groups: one for sleep, one for no sleep, and one that received the artificial deep sleep stimulus.

The next day, when reintroduced to the box, one side contained a new texture. As mice are naturally curious, their time spent in the newly textured area indicated their memory of the original environment. The results showed that while uninhibited, sleep-deprived mice had difficulty distinguishing between the two sides, both the sleep group and the stimulated sleep group spent significantly more time in the new area.

The research team intends to examine whether similar benefits can be achieved in humans through non-invasive brain activity stimulation techniques such as transcranial electrical stimulation. However, Vyazovski cautions against the idea that sleep can be fully replaced. “We recognize two sleep types: NREM and REM,” he notes, emphasizing that our understanding of the transition between these two states and the completion of sleep remains limited.