Method for Selective REM Sleep Deprivation using The Selective Nose Flicking for Forgetting REM (SNiFFer)

Sleep is broadly categorized into Rapid Eye Movement (REM) and non-REM stages, and various sleep deprivation techniques have been developed to study their functions. Traditional methods-such as mechanical stimulation or dropping the animal during REM sleep-often lead to rapid habituation and unintended stress effects, making interpretation difficult. Here, we introduce a novel, mild, and gentle method for REM sleep deprivation in rodents: SNiFFer. Rodents are known to be highly sensitive to nasal stimuli. In this method, a soft paintbrush gently strokes the animal's nose during REM sleep, reliably triggering arousal. To selectively apply this technique during REM sleep, we utilized an AI-based real-time Electroencephalography (EEG) sleep-stage classification system. The intervention was triggered only during REM episodes, and a yoked control group was included, receiving the same stimulation pattern regardless of sleep state. We further applied SNiFFer in a Trace Fear Conditioning paradigm to test whether REM sleep deprivation within 6 h after learning interferes with memory consolidation. Compared to yoked controls, SNiFFer-treated animals showed a significant decrease in total REM episode and REM episode duration, indicating the method's specificity and efficacy. In conclusion, the SNiFFer technique offers a highly selective, minimally invasive tactile approach for REM sleep deprivation in mice. It enables precise control of experimental conditions and opens new possibilities for investigating REM sleep's role in memory and cognition-with a ticklish twist.