Cerebellum

Show numbers

a. Vermal zone of cerebellum

Shown in Image 9, this zone is the most medial of the three functional zones of the cerebellum (see text accompanying Image 9). The vermal zone is concerned with maintaining our posture and balance.

Show list

a.
Vermal zone of cerebellum
b.
Medial zone of cerebellum (paravermal zone)
c.
Lateral zone of cerebellum
1.
Superior colliculi
2.
Inferior colliculi
3.
Vermis
4.
Horizontal fissure of cerebellum
5.
Posterior superior fissure of cerebellum
6.
Posterior lobe of cerebellum
7.
Anterior lobe of cerebellum (anterior cerebellar cortex)
8.
Primary cerebellar fissure

In this view we see:

The posterior view of the cerebellum showing the many transversely oriented folia.
Dashed vertical lines indicating longitudinal zones of the cerebellum, showing the three functional zones:

vermis – the most medial vermal zone consisting largely of the midline vermis;
medial or paravermal zone – where each medial zone occupies a strip of cortex on each side of the vermal zone;
lateral zone – these zones occupy the bulk of each cerebellar hemisphere laterally.

The cerebellum is a complicated structure that is difficult to conceptualise. However, the vertical functional zones provide a relatively simple way to correlate structure with function.

Cerebellum

Location

The position of the cerebellum is shown relative to the right cerebral hemisphere in Image 1, and in relation to the brainstem in Image 2. The relative positions of the brainstem and cerebellum are also apparent in the anterior view of both structures shown in Image 8.

Structure

The most visible features on the surface of the cerebellum are the horizontal ridges called folia. The folia are the result of the convoluted folding of the cerebellar cortex as it develops.

Another external feature is the midline region called the vermis, located between the two cerebellar hemispheres. The following functional zones (derived from animal studies) allow us to correlate function, structure and location, with projections from each zone extending to different deep cerebellar nuclei, which in turn project to different areas of the brain:

vermis – the most medial vermal zone consisting largely of the midline vermis projects to the fastigial nucleus, which in turn projects to vestibular nuclei and the reticular formation;
medial (or paravermal or intermediate) zone – each medial zone occupies a strip of cortex on each side of the vermal zone, which projects to the interposed nucleus, and then to the red nuclei and thalami;
lateral zone – these zones occupy the bulk of each cerebellar hemisphere laterally, projecting to the dentate nucleus, which projects to motor and premotor areas of the cerebral cortex.

Traditionally, the cerebellum has been divided into lobes and one of these lobes, the flocculonodular lobe, can be seen in Image 8.

Function

The cerebellum acts as a movement control centre through the extensive cerebrocerebellar and spinocerebellar connections of the cerebrum and spinal cord.

Generally, the vermis is more concerned with axial trunk muscles and the hemispheres with limb movements.

Vermal zone – regulates posture and stereotyped movements that are programmed in the brainstem and spinal cord.

Medial zone – adjusts limb movement by comparing commands from the motor cortex with the actual position and velocity of each limb.

Lateral zone – is involved in the planning of skilled movements by influencing the output of the motor cortex. These are the movements that improve with practice, such as playing a piano or playing sport. The cerebellum of skilled tennis players makes calculations based on past events that enable players to hit the ball in a shorter time than would otherwise be possible.

Cognitive functions – have been postulated for the cerebellum. Although the cerebellum has a well-proven role in motor learning, further research is required to definitively establish participation in activities such as language processing.