The cerebellum is the center of fine motor skills, balance and coordination of the brain. It processes proprioceptive information from the periphery and integrates it with the cerebrum’s intention to move, allowing us to execute smooth and accurate motions.

The cerebellum is divided into two hemispheres by a central worm-like structure called the vermis. Each hemisphere coordinates the movements of the ipsilateral limb, whereas balance and tone of axial movements is regulated by the vermis. An example of an everyday movement controlled by the vermis is walking.

Just like the cerebrum, the cerebellum also comprises lobes and fissures.

The three main lobes of the cerebellum are:

• Anterior lobe: located on the superior surface of the cerebellum, this lobe makes up the corpus cerebelli with the posterior lobe.
• Posterior lobe: located on the inferior surface of the cerebellum, this lobe makes up the corpus cerebelli with the anterior lobe.
• Flocculonodular lobe: located on the ventral surface of the cerebellum

Fissures:

• The posterolateral fissure: divides the corpus cerebelli from the flocculonodular lobe.
• The primary fissure: divides the corpus cerebelli into the anterior lobe and the posterior lobe.
• The horizontal fissure: the most obvious fissure, it divides the superior and inferior surfaces of the cerebellum and serves a useful landmark.


Functionally, the cerebellum can also be organized into 3 areas:

• Vestibulocerebellum aka. the Archicerebellum - The evolutionarily oldest part of the cerebellum, the vestibulocerebellum is the only part of the cerebellum that can be found in aquatic vertebrates, such as fish. It’s function is to maintain balance and regulate ocular reflexes, mainly object fixation—as such, the vestibulocerebellum receives many inputs from the vestibular nuclei. The flocculonodular lobe and the lingula (which is part of the anterior lobe) functionally make up the vestibulocerebellum.
• Spinocerebellum aka. the Paleocerebellum - This part of the cerebellum can be found in terrestrial beings with limbs and is mainly responsible for the movements of the body and limbs. Anatomically, this functional area corresponds to the vermis and the intermediate zone of the cerebellar hemispheres (the area of the cerebellar hemispheres immediate adjacent to the vermis). It receives a great amount of proprioceptive inputs and its outputs provide modulation for descending motor fibers.
• Cerebrocerebellum aka. the Neocerebellum - The most evolutionarily recent part of the cerebellum, the cerebrocerebellum is involved in the planning and smooth execution of voluntary movements. The cerebellum is connected to the rest of the CNS via three bilateral peduncles(so 6 peduncles in total, 3 pairs).



Damage to the cerebellum results into something called “ataxia”: the inability to coordinate one’s movements. This can translate into being unable to walk and struggling with balance, as well as not being able to correctly aim an outstretched limb to touch a target.