This illustration shows the cerebellum's location in the human brain. Illustration: Alan Hoffring, National Cancer Institute, public domain image.
About half your entire brain's neurons are found in the cerebellum; it's a tightly-packed twin-hemisphere hindbrain region, with much denser surface folds than the outer surface of the main brain - the cerebral cortex (Latin for brain bark). Its hundreds of millions of neurons primarily relay information between muscles of the body and motor control regions of the cerebral cortex. It acts as a comparator, using mismatches between intentions and actual movement as an error-correction guide to produce fine, complex movements - comparing mental motor control commands with actual movement to correct and refine motion.
Most information about the cerebellum's function is derived from examining humans and animals with damage to the region. Subjects with cerebellar damage suffer from major motor control problems, ipsilateral (on the opposite side of the body) to the damaged cerebellar lobe. While they can still produce movement, it is uncoordinated, mistimed, or erratic. Because of this and fMRI scans, it is believed the region fine tunes and coordinates, rather than initiates or selects movement.
However, recent findings indicate the cerebellum is not solely motor-related. It also activates during functions related to mental imagery, attention, motor learning and language.
The cerebellum also develops in response to external stimulation, so in response to practice, specific genes or gene groups get switched on and off, strengthening the circuits to consolidate and perfect complex tasks. Snf2h functions as a master coordinator, orchestrating this complex, ongoing process. Such master genes are called epigenetic (above the gene) regulators, and they adapt according to environmental cues such as diet or stress, then adjust which genes are switched on or off.
Dr. David Picketts of the Ottawa Hospital Research Institute and University of Ottawa led the team which discovered Snf2h along the chromatin (DNA strands) in the nuclei of the brain's neural stem cells. According to Dr. Picketts, master epigenetic regulators like Snf2h affect memory, behaviour and learning.
Silencing Snf2h in developing mice embryos results in cerebella one-third the normal size, with consequent errors in walking, balance and coordinated movement. Such impairment, cerebellar ataxia, is common among sufferers of neurodegenerative diseases.
When cerebellar stem cells divide, en route to specializing as specific neurons, Snf2h determines which genes will be activated and which genes will be curled up inaccessibly along the DNA strands. Without its guidance, some vital genes remain inactivated, while others which hinder development remain switched on. The result is sparser neurons, which don't respond and adapt to external signals efficiently. Gene expression in the cerebellum becomes progressively more disorganized, leading to cerebellar ataxia and premature death for the afflicted.
Source: Researchers find gene critical for development of brain motor centre, News Release, June 20, 2014, Paddy Moore, Ottawa Hospital Research Institute