Cats twitch when they sleep primarily because they are dreaming during the REM (Rapid Eye Movement) stage of sleep. During this stage, their brains are very active, which can cause involuntary muscle contractions that lead to twitching movements of their paws, whiskers, ears, tail, or even small vocalizations. These twitches are normal and part of the healthy sleep cycle, reflecting the cat's brain processing daily experiences or "practicing" hunting behaviors. Additionally, twitching can also be caused by muscle spasms or hypnic jerks as cats enter or shift within sleep phases. For kittens, twitching is more frequent because their nervous systems are still developing and twitching helps stimulate and develop motor skills. However, if the twitching is severe, prolonged, happens while the cat is awake, or is accompanied by other symptoms like disorientation, it could indicate a medical issue like seizures and would warrant a vet's attention. In summary, normal twitching during sleep in cats is a sign they are dreaming and experiencing healthy neurological reflexes, especially during REM sleep.
