Motor Systems 3 - Ebner

Question 1

Cerebellum is organized contralaterally, bilaterally, or ipsilaterally?

Answer 1

Ipsilaterally

Question 2

What cells are the origins of the parallel fiber network?

Answer 2

Granule cells

Question 3

What are the three inhibitory interneurons of the cerebellar cortex?
What NT do they use?
What are they activated by?

Answer 3

Stellate, basket, and Golgi cells
All use GABA
All excited by parallel fibers

Question 4

Are granule cells excitatory or inhibitory?

What NT do they use?

Answer 4

Excitatory

They use glutamate

Question 5

What do purkinje cells receive afferent input from?

Answer 5

They receive EXCITATORY input from parallel fibers and climbing fibers

Question 6

What do purkinje cells output to?

Answer 6

They are inhibitory to cerebellar nuclei/vestibular nucleus

Question 7

Describe the differences in input between mossy fibers and climbing fibers and their effects on purkinje cells:

Answer 7

a. Mossy fiber afferents:
- Originate in spine and brainstem
- Synapse on granule cells (excitatory, glutamate)
- Produce “simple spikes” in Purkinje cells
- High frequency discharge
- Encode temporal and intensity information

b. Climbing fiber afferents:
- Originate in inferior olive ONLY
- Monosynaptic to Purkinje cells
- Powerful excitation
- Produce “complex spikes” in Purkinje cells
- Low frequency discharge
- May encode “teaching signal”

Question 8

What is the vestibulocerebellum in charge of?

Answer 8

Vestibular, balance, and eye movements

Question 9

What kind of input does the vestibulocerebellum get?

Answer 9

MOSSY FIBERS carry info from:
Semicircular canals
Otoliths
Visual info from parietal and occipital to pontine nuclei

Question 10

Where does the vestibuloverebellum send its outputs?

Answer 10

Projects to vestibular and fastigial nuclei (medial and lateral)

Medial vestibulospinal tract
(controls trunk/neck muscles)

Lateral vestibulospinal tract
(controls limb muscles)

Gaze centers
(controls eye movements)

Question 11

If the vestibulocerebellum is damaged what kinds of signs do you get?

Answer 11

• Disturbances of equilibrium/balance – fall toward side of lesion
• Nystagmus
• Loss of smooth pursuit eye movements
• (Lesioning the fastigial nucleus has similar effects)

Question 12

What is the spinocerebellum in charge of?

Answer 12

Monitor and coordinate ongoing movements, especially in lower limbs

(This wasn’t from lecture, but I think it’s right)

Question 13

What kind of problems will you get if you injure the spinocerebellum?

Answer 13

Gait ataxia
Hypotonia (this is odd because its a central lesion)
Voluntary tremor (shake when you move)
Limb ataxia/dysmetria
Problems with timing (disdiadochokinesia)

Question 14

Where does the cerebrocerebellum git its inputs from?

Answer 14

Pontine nuclei,

from sensory, motor, premotor, and parietal cortices

Question 15

Where do the outputs of the cerebrocerebellum go?

Answer 15

Via dentate nuclei:

Ventral nucleus of thalamus to motor/premotor in order to control corticospinal tract
PRefrontal area
red nucleus to rubrospinal tract

Question 16

What kind of problems do you get with a lesion of the cerebrocerebellum?

Answer 16

Ataxia of the fienst movements
-shaping of hands, writing
(Same effects when dentate nucleus is damaged

Question 17

Where does the climbing fiber system arise from? How is it organized in comparison to the purkinje cells?

Answer 17

It arises from the contralateral inferior olive

It projects parasagitally to Purkinje fibers orthogonal (perpendicular) to parallel fibers

Question 18

So overall, cerebellum’s main job?

Answer 18

Produce smooth and coordinated movements
Help movement timing
Create motor learning
Predict and improve consequences of motor movement

Question 19

How do Purkinje cells influence motor learning?

Answer 19

Through long term depression of parallel fibers at the purkinje cell synapse
Conjunction of climbing fiber and parallel fibers to Purkinje cells

Question 20

How does Long term depression occur in the cerebellum?

Answer 20

Basically parallel fibers and climbing fibers have to be activated simultaneously on Purkinje cells. The Ca influx created by the climbing fibers works to actually decrease the response of AMPA receptors to glutamate at parallel fiber synapses

So LTD selectively reduces transmission at the parallel synapse.

Question 21

What happens in mice who have Purkinje cell specific loss of LTD?

(specifically when to their VOR plasticity?)

Answer 21

The lose their VOR plasticity

Their brain is unable to mold the new sort of input that they are getting from magnified lenses and they are never able to learn it.