Artificial Brain Stimulation Mimics Deep Sleep Benefits in Awake Mice

Researchers at the University of Wisconsin-Madison genetically engineered mice so their neuronal activity could be switched off using light. They implanted a probe into one half of each animal’s brain and kept the mice awake for five hours by giving them new things to explore.

Near the end of the five-hour wake period, the light probe was repeatedly turned on and off for 30 minutes, mimicking the slow-wave activity that occurs during non-rapid eye movement sleep.

NREM sleep makes up around 80 per cent of sleep in adults. During NREM sleep the brain’s cortex repeatedly fires signals at the exact same time and then shuts those neurons off. After the artificial stimulation, brain recordings showed that the stimulated side of the brain did not show the usual signs of exhaustion caused by sleep deprivation.

“Because that small part of the brain did its decluttering while awake, it no longer needed extra deep sleep afterwards,” Chiara Cirelli said. The team next tested whether the stimulation preserved memory. Mice explored a square box with carpet of the same texture on both sides for 15 minutes.

They were then assigned to a normal-sleep group, a sleep-deprived group, or a sleep-deprived group that received the artificial stimulation. The next day the mice returned to the box, now with one side bearing a new texture. Sleep-deprived mice without stimulation struggled to distinguish the textures, while both the normal-sleep group and the stimulated sleep-deprived group spent more time on the new side.

The researchers plan to study whether similar effects could be induced in people using transcranial electrical stimulation. Vladyslav Vyazovskiy of the University of Oxford said it should be possible, at least in theory and to some extent, to replicate these results in humans.