Cats are experts when it comes to devoting more than 2/3rds of their day sleeping. But have you ever noticed that during sleep, cats will often twitch?
There are two basic sleep cycles, active or rapid eye movement (REM) sleep and non-rapid eye movement sleep, which has three stages.
- N1: This stage occurs right after the cat falls asleep and involves light sleep.
- N2: During the next stage, the muscles relax and the brain activity slows.
- N3: The third stage is deep sleep, at which point it may be hard to wake the cat.
The purpose of REM sleep is still not entirely understood, but it is thought to stimulate areas of the brain that are essential to learning and exercising important neural connections. Active (REM) sleep produces rapid movement of the eyes and the characteristic twitching of the limbs, toes, ears, whiskers and eyes (hence the name rapid eye movement). During REM sleep, the brain is almost as active as when the cat is awake, heart rate and blood pressure are increased. Cats spend approximately 24% of their sleep cycle in active sleep.
One study found that rats who were repeatedly deprived of REM sleep had a considerably shortened lifespan from 2-3 years to five weeks.