Cerebellum

The cerebellum is the dense, finely-folded structure at the back and bottom of the brain. Its name means "little brain" in Latin, and it deserves the name: it contains more neurons than the entire rest of the brain combined — somewhere around 70 of the brain's 86 billion neurons sit here.

What it does

The cerebellum was long thought to be mostly about movement. That's true but incomplete.

Motor functions:

• Fine-tuning movement timing and accuracy
• Maintaining balance and posture
• Coordinating eye movements
• Motor learning — learning to ride a bike, throw, dance

Cognitive and emotional functions (more recently recognised):

• Language processing
• Attention and working memory
• Emotional regulation
• Implicit learning and prediction

Cerebellar damage can produce ataxia (uncoordinated movement) and cerebellar cognitive affective syndrome — a constellation of executive, language, and emotional symptoms.

In neuroimaging

The cerebellum is segmented as part of standard volumetric pipelines (FreeSurfer, FastSurfer). Total cerebellar volume and lobular breakdowns are reported, and the white-matter tracts connecting it to the rest of the brain (the cerebellar peduncles) are tracked in diffusion imaging studies.

Cerebellar volume declines with age, but typically more slowly than cortical volume. Cerebellar atrophy is a feature of several conditions including chronic alcoholism, certain genetic ataxias, and Parkinson's disease.