The cerebellum and motor learning

Question 1

What are the roles of the cerebellum?

Answer 1

Maintenance of balance and posture

Coordination of voluntary movements

Motor learning

Cognitive functions

“The greater comperator” - compares movement intended with movement actually occuring. Sends correctional signal to brain areas involved in planning, initiation and execution

Question 2

Outline the location and structure of the cerebellum

Answer 2

Inferior and posterior to brain cerebral cortices.

Comprised of vestibulocerebellum, spinocerebellum (responsible for muscle tone and posture)

Question 3

What are the clinical symptoms and signs of cerebellar dysfunction?

Answer 3

Lesions cause:
- Dysmetria: movement not stopped in times

• Dysnergia: decomposition of complex movements
• Dysdiaochokinesia: reduced ability to perform rapidly alternating movements
• Intentional tremor- tremor arising when trying to perform a goal-directed movement
• Dysarthria- articulation incoordination. Incoordination in respiratory muscles and in larynx leading to uneven speech strength and velocity

Question 4

What effects would a lesion on the vestibularcerebellar pathway have?

Answer 4

Nystagmus- involuntary, rhythmic, repeated oscillations of one/both eyes in all directions of view. Movement minimises ability to focus on one point (fixation)

Question 5

What effects would a lesion on the spinocerebellar pathway have?

Answer 5

Gait ataxia- unsteadiness of walking and disturbance of limb tone (hypotonia) and posture

Question 6

Which two fibres provide INPUT to the cerebellar?

And from the cerebellar what happens?

Answer 6

MOSSY FIBRES- from spinal cord and brainstem

CLIMBING FIBRES- from inferior olivary nucleus

Output to deep cerebellar nuclei to: thalamus, vestibular nuclei, red nucleus

Question 7

How does the cerebellum interact with other parts of the brain?

Answer 7

A feedforward control system is needed for fast movements as a feedback system is too slow.

From the motor cortex to effector which provides MOTOR OUTPUT

Mossy fibres from motor cortex and sensor, as wellas climbing fibres (error signals) project onto the cerebellar. This also projects onto an effector organ causing MOTOR OUTPUT

The sensor provides advance information

Question 8

What causes cerebellar dysfunction?

Answer 8

Genetics: Inherited causes are rare e.g. Fredericks ataxia, Spinocerebellar degeneration, ataxia-telengiectasia, von Hippel Lindau

Acquired symmetrical ataxia e.g. degenerative , immune, metabolic (B12/thyroid/coeliac), drugs: alcohol, phenytoin

Focal cerebellar pathology (asymmmetic)