Organ
Cerebellum
Also called Little brain
The "little brain" that holds most of your neurons and makes every move smooth.
The cerebellum is the wrinkly ball tucked under the back of your brain. It makes your movements smooth, steady and well-timed, and it keeps you balanced. It takes up only about a tenth of the brain's space, yet it holds about 69 billion of the brain's roughly 86 billion neurons, most of them tiny granule cells. It also helps with timing, prediction, and even some thinking and feelings.
Where it is
At the back and bottom of the head, just above where your neck meets your skull. It sits under the back of the big brain and behind the brainstem.
What it does
Smooth, accurate movement
It fine-tunes the force, direction and timing of your muscles, so you can pick up a cup without knocking it over.
Balance and posture
Using signals from your inner ear and your body, it keeps you upright and steady, even on a swaying bus.
Learning skills
Riding a bike, typing or playing piano starts out clumsy and slowly becomes automatic. The cerebellum stores much of that practice.
Timing and prediction
It helps time your movements and predicts what they should feel like.
Help with thinking and feeling
Studies of people with damage here show it also helps with planning, language, attention and emotion, not just movement.
Think of it as an autopilot and an editor rolled into one: it compares the move you meant to make with the move you actually made, and quietly fixes the difference.
Inside the cerebellum
- Anterior lobeThe top front part of the cerebellum, keeping your walk and posture smooth.
- Posterior lobeThe cerebellum's large back part, polishing skilled moves and even helping you think.
- Flocculonodular lobeThe oldest part of the cerebellum, keeping you balanced and your eyes steady.
- VermisThe worm-shaped middle strip of the cerebellum, keeping your body balanced and upright.
- Arbor vitaeThe "tree of life": branching white wiring hidden inside the cerebellum.
- Deep cerebellar nucleiThe cerebellum's hidden exit doors, sending out its final polished messages.
Works with
- PonsMessages from the cortex reach the cerebellum by passing through the pons, its main input bridge.
- Deep cerebellar nucleiAlmost everything the cerebellum decides leaves through these buried clusters of cells.
- Ventral lateral nucleus of the thalamusThe cerebellum's corrections travel through this relay in the thalamus up to the movement areas of the cortex.
- Primary motor cortexThe motor cortex sends out movement commands, and the cerebellum helps polish them into smooth action.
- Vestibulocochlear nerve (VIII)Balance signals from the inner ear feed into the cerebellum to keep you steady.
- Purkinje cellThese big, tree-shaped cells are the only way out of the cerebellum's surface, and they send finely tuned "slow down" signals.
When it goes wrong
Ataxia (clumsy, unsteady movement)
Damage from a stroke, tumor or disease can make walking wobbly and wide-legged, speech slurred, and hands shaky when reaching. Doctors call this ataxia, from Greek for "without order".
Alcohol
The cerebellum is very sensitive to alcohol. That is why drunk people stagger, slur their words and fail the police tests of walking a straight line or touching their nose, which are really cerebellum checks. Years of heavy drinking can cause lasting damage here.
Changes in thinking and mood
Some people with cerebellum damage also have trouble planning, finding words or controlling emotions. Scientists only widely recognized this link in the last few decades.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Surprising facts
- It controls the same side of the body. The big brain works crosswise, but the cerebellum's wiring crosses twice, so your left cerebellum helps your left hand.
- You cannot tickle yourself partly because your cerebellum predicts exactly what your own fingers will feel and turns the feeling down.
- A few people have been born with no cerebellum at all. Many of them manage surprisingly well, and some only find out as adults, showing how much the rest of the brain can adapt.
By the numbers
Where the name comes from
Latin for "little brain". It looks like a small brain of its own, tucked under the big one, which is called the cerebrum.
Learn it in a lesson
- The big pictureCerebrum, cerebellum and brainstem. A short guided lesson in 3D.
- The cerebellumSmooth, balanced, well-timed movement. A short guided lesson in 3D.
Quick quiz
2 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the cerebellum?
Show the answer
Smooth, accurate movement. It fine-tunes the force, direction and timing of your muscles, so you can pick up a cup without knocking it over.
Smooth, accurate movement. It fine-tunes the force, direction and timing of your muscles, so you can pick up a cup without knocking it over.
Which part fits this description? "Like an autopilot and an editor rolled into one: it compares the move you meant to make with the move you actually made, and quietly fixes the difference."
Show the answer
Cerebellum. It is the cerebellum. The "little brain" that holds most of your neurons and makes every move smooth.
Cerebellum. It is the cerebellum. The "little brain" that holds most of your neurons and makes every move smooth.
These parts now come back in your daily review, just before you would forget them.
Practice these parts in 3DSources
- Neuroanatomy, Cerebellum, StatPearls, NCBI Bookshelf
- 1.4 The Brain: Structure and Function, OpenStax, Introduction to Behavioral Neuroscience
- Review: The Cerebellum and Cognition, Massachusetts General Hospital
Spotted a mistake? Tell us.
Explore the cerebellum in 3D
Turn it around, zoom inside and see how it connects to the rest of the brain, then test yourself with quick quizzes.
Open it in 3D