By inducing specific patterns of activity in small portions of the brain in awake mice, researchers have triggered a recalibration of neural connections that normally only occurs during sleep. This new approach offset the effects of sleep deprivation in memory tasks.

Cirelli and her colleagues previously showed that, when sleep-deprived, both rats and humans can exhibit local slow-wave brain activity — a hallmark of NREM sleep — while awake. These deprivation-induced dips into sleep-like activity may have been too sporadic and brief to be beneficial, but the findings raised questions about the possible effects of a longer, more systematic version of this activity.

In the new research, the authors used a combination of light-pulsing implants and genetic modifications to induce rhythmic on-and-off activity in one side of the brains of sleep deprived mice for 30 minutes at a time, mimicking patterns that occur during NREM sleep.

When mice subsequently slept, slow-wave activity was lower in the specific brain regions the authors had stimulated, indicating less need for sleep. Additional experiments suggested that this effect hinged not on the overall reduction in neuronal firing, which some scientists had suggested was critical to recover from wake-induced neuronal fatigue, but rather on the specific alternating on-and-off pattern of activity.