Your cat is almost certainly twitching during REM sleep, the phase of deep sleep when the brain is highly active but the body is mostly paralyzed. Small bursts of movement break through that paralysis, causing the paws, whiskers, ears, or tail to shake, jerk, or flutter. It’s one of the most common things cat owners notice, and in the vast majority of cases, it’s completely normal.
What Happens in Your Cat’s Brain During Sleep
Cats spend a significant portion of their day sleeping, and like humans, they cycle through different sleep stages. The twitching you see happens during REM (rapid eye movement) sleep, when brain activity spikes to near-waking levels. Scientists confirmed back in the 1960s that cats experience REM sleep, complete with darting eye movements beneath closed lids and bursts of limb twitching.
During REM sleep, the brain sends a signal that essentially shuts down voluntary muscle control. This state, called atonia, keeps your cat from physically acting out whatever its brain is processing. But the shutdown isn’t perfect. Small twitches punch through the paralysis in quick bursts, which is why you’ll see a paw paddle, a lip quiver, or a tail flick. These movements are generated directly by circuits in the brainstem, not by higher brain regions. Research in both cats and rats has shown that twitching continues even when the forebrain is completely disconnected from the brainstem, meaning the twitches aren’t simply spillover from dreams. They appear to be a fundamental feature of how the sleeping brain maintains and organizes motor pathways.
That said, cats do seem to dream. Their brain wave patterns during REM closely resemble waking activity, and some researchers believe the twitching overlaps with dream content at least some of the time. If your cat looks like it’s chasing something in its sleep, it might be.
What Normal Sleep Twitching Looks Like
Normal REM twitching is gentle and intermittent. You might see:
- Paw twitches or paddling motions that last a few seconds
- Whisker or ear fluttering
- Tail flicking
- Soft vocalizations like chirps or quiet meows
- Rapid eye movement visible under closed eyelids
The key feature of normal twitching is that it stops as soon as your cat wakes up. If you gently call your cat’s name or make a sound, a twitching cat will rouse normally, look around, and behave like its usual self. The movements are also localized and small rather than involving the whole body in rigid or violent shaking.
Cold Temperatures Can Cause Shivering
If the shaking looks more like sustained shivering than brief twitches, your cat might simply be cold. Cats are comfortable in the same temperature range most people prefer, roughly 65 to 80°F (18 to 27°C). Below that range, a sleeping cat may shiver to generate warmth, especially if it’s short-haired, very young, very old, or thin. Research on cats and ambient temperature shows that both cold environments (down to 45°F/7°C) and overly warm ones disrupt normal sleep architecture, reducing the amount of time cats spend in deep sleep stages.
If your cat tends to curl into a tight ball while sleeping or seeks out warm spots like sunny windowsills and radiators, it may be telling you the room is too cool. Providing a warm bed or blanket in a draft-free area is usually enough to resolve temperature-related shivering.
When Shaking Signals Something Else
In a small number of cases, shaking during sleep points to a health issue worth investigating. The distinction comes down to what the shaking looks like and whether it also happens when your cat is awake.
Tremors are sustained, uncontrollable shaking that can affect one body part or the whole body. Unlike REM twitches, tremors don’t stop neatly when the cat wakes up. They may be visible during rest and during waking hours. Tremors can result from pain, neurological problems, toxin exposure, or metabolic issues like low blood sugar. Cats with low blood sugar often show other signs too: weakness, lack of coordination, lethargy, or vomiting.
Seizures look dramatically different from sleep twitching. A seizing cat typically has full-body convulsions with stiff, rigid limbs. It may lose consciousness, drool excessively, or lose control of its bladder or bowels. The cat won’t respond to its name or to touch during the episode, and afterward it often appears confused, disoriented, or wobbly for minutes to hours. If you’ve seen your cat do this, a veterinary evaluation is important.
A useful test: if you can gently wake your cat and it responds normally, stretches, and goes about its business, you’re almost certainly looking at ordinary sleep twitching. If the shaking continues after waking or your cat seems confused and uncoordinated, something else is going on.
Sleep Changes in Older Cats
If your cat is a senior (roughly 11 years or older) and the sleep shaking seems new or more intense, age-related brain changes could play a role. Cats can develop cognitive dysfunction syndrome, a condition similar to dementia in humans. One of the hallmarks is disrupted sleep-wake cycles, with increased nighttime waking, restlessness, and vocalization.
The underlying cause involves physical deterioration of brain cells in regions that regulate sleep and alertness. In aged cats, the neurons in these areas accumulate damage, including abnormal structures inside the cells and degeneration of nerve fibers. These changes can alter REM sleep patterns, potentially increasing or changing the character of sleep movements. Owners of cats with cognitive dysfunction commonly report excessive vocalization, nighttime waking, aimless wandering, and changes in how the cat interacts with people. If your older cat’s sleep behavior has shifted alongside any of these signs, cognitive decline is worth discussing with your vet.
Should You Wake a Twitching Cat?
Generally, no. REM sleep serves important biological functions, and interrupting it repeatedly isn’t ideal. If you’re concerned about a specific episode, a gentle voice or soft sound is enough to check whether your cat rouses normally. But if the twitching is the small, intermittent kind described above, your cat is just sleeping deeply, and its brain and body are doing exactly what they’re supposed to do.