Motor Systems: Cerebellum

Question 1

What are the deep cerebellar nuclei from lateral to medial? What are their functions?

Answer 1

(Don’t Eat Green Frogs)
Dentate, Emboliform, Globose, Fastigial
-Excitatory and lead to activation of neurons in motor control centers

Question 2

What are mossy fibers? What is their purpose? Where do they terminate in the cerebellum?

Answer 2

Mossy fibers are a heterogeneous group of afferents carrying reference input and efference copy. ALL afferent inputs to the cerebellum, except for inputs from the inferior olives (climbing fibers), are mossy fibers.

*Produce simple spikes in Purkinje cells, high frequency discharge

Terminate in:

• Deep cerebellar nuclei (directly excite)
• Cerebellar cortex (excite granule cells that indirectly excite Purkinje cells)

Question 3

Where do mossy fibers primarily form from?

Answer 3

• the periphery via spin and cuneocerebellar tracts
• Motoneurons, motor interneurons, and central pattern generators via spino and cuneocerebellar tracts
• Vestibular info, arriving via the vestibular nerve and nuclei
• Cortex, including motor, premotor, somatosensory, and visual areas, via a synapse in the pontine nuclei

Question 4

What are Purkinje cells?

Answer 4

Only output neuron, inhibitory (GABA) to cerebellar nuclei/vestibular nucleus; receives input from parallel fiber and climbing fibers

Question 5

What are granule cells?

Answer 5

Origin of parallel fiber system, excitatory (glutamate) to Purkinje cells and inhibitory interneurons.

Question 6

What are the three inhibitory interneurons?

Answer 6

Stellate, basket, and Golgi cells. All excited by parallel fibers

Question 7

What are climbing fibers?

Answer 7

• Come solely from contralateral inferior olive.
• Monosynaptic to Purkinje cells, resulting in powerful excitation known as complex spikes
• Low frequency discharge
• May encode teaching signal

Question 8

Where does the vestibulocerebellum (flocculonodular lobe and vermis) project to?

Answer 8

• Vestibular and fastigial nuclei
• Medial vestibulospinal tract (controls trunk/neck muscles)
• Lateral vestibulospinal tract (controls limb muscles)
• Gaze centers (controls eye movements)

Question 9

The following symptoms are due to disorders of what division of the cerebellum?

• Disturbances of equilibrium (fall toward side of lesion)
• Nystagmus
• Loss of smooth pursuit eye movements

Answer 9

Vestibulocerebellum. Lesioning fastigial nucleus has similar effects.

Question 10

Dorsal spinocerebellar tract

Answer 10

Type of info: Reafference
Body parts: Legs and trunk
Arises from: Clarke’s nucleus
Enters thru: Restiform body/inferior cerebellar peduncle

Question 11

Ventral spinocerebellar tract

Answer 11

Type of info: Efference copy
Body parts: Legs and trunk
Arises from: Ventral horn
Enters thru: Superior cerebellar peduncle

Question 12

Cuneocerebellar tract

Answer 12

Type of info: Reafference
Body parts: Arms
Arises from: External cuneate nucleus
Enters thru: Restiform body/inferior cerebellar peduncle

Question 13

Rostral spinocerebellar tract

Answer 13

Type of info: Efference copy
Body parts: Arms
Arises from: Ventral horn
Enters thru: Restiform body/inferior cerebellar peduncle

Question 14

The following symptoms are due to a disorder of what area of the cerebellum:

• Disturbances of gait (vermis)
• Hypotonia
• Action tremor
• Limb ataxia/dysmetria
• Disorders of timing (dysdiadochokinesia)
• Decomposition of movements

Answer 14

Spinocerebellum. Lesioning the emboli form and globose nuclei has similar effects.

Question 15

Where does the spinocerebellum project to?

Answer 15

• Vermis projects to fastigial nucleus (reticulospinal tract and vestibulospinal)
• Intermediate zone projects to globose and emboliform nuclei which project to red nucleus (controls rubrospinal tract) and ventral lateral thalamus and the motor cortex (controls corticospinal tract)

Question 16

Where does the cerebrocerebellum (cerebellar hemispheres lateral zones) get input from?

Answer 16

-Pontine nuclei

Question 17

Where does the cerebrocerebellum project to

Answer 17

Via dentate nuclei to VL of thalamus, prefrontal areas, and red nucleus

Question 18

Damage to what area of cerebellum results in the following symptoms:

• Ataxia of finest movements
• Cognitive deficits?

Answer 18

Cerebrocerebellum (lesioning the dentate nucleus has similar effects).

Question 19

How does the cerebellum predict the consequences of a motor action?

Answer 19

By comparing efferent copies (what is supposed to happen) with reafferents (what actually is happening). Learning is used to improve these predictions.