Motor System 3: Cerebellum

Question 1

What, broadly, is the role of the cerebellum?

Answer 1

It compares the intention of a motion with the outcome, and sends out predictive and corrective signals.

Question 2

Does the cerebellum have direct output to the muscles?

Answer 2

No.

Question 3

What do lesions to the cerebellum broadly cause / not cause? (3 things)

Answer 3

Loss of spatial accuracy, coordination (ataxia)
Impairment of muscle tone and balance
Do NOT cause sensory loss or loss of strength

Question 4

What are the folia of the cerebellum?

Answer 4

Thin gyri…

Question 5

Is there a midline groove (or other structure) that divides the cerebellum into two halves?

Answer 5

No.

Question 6

What function do the (deep) cerebellar nuclei serve?

Answer 6

Sources of output from the cerebellum.

Question 7

What are the 3 lobes of the cerebellum? What fissures divide them?

Answer 7

Anterior, posterior, and flocculonodular lobes.
Primary fissure divides anterior from posterior lobe.
Posterolateral fissure divides posterior from flocculonodular lobe.

Question 8

What characteristic defines the functional regions of the cerebellum?

Answer 8

Source of inputs.

Question 9

What are the 2 systems of input to the cerebellum?

Answer 9

Climbing fiber system and the mossy-fiber, parallel-fiber system.

Question 10

Where do climbing fibers come from? Where do they travel in the brain stem? Where do they go in the cerebellum? Type of synapse?

Answer 10

Origin: Inferior olivary nucleus
Path: Cross midline, travels up inferior cerebellar peduncle (ICP)
Destination: Purkinje cells (wrap all around their dendrites)
Synapse: Excitatory glutamatergic

Question 11

Where do mossy fibers come from? Where do they travel in the brain stem? Where do they go in the cerebellum? Type of synapse?

Answer 11

Origin: “All sensory modalities” (including sensory nuclei)
Path: Up the inferior cerebellar peduncle (ICP)
Destination: Granular cells
Synapse type: Excitatory glutamatergic

Question 12

How do the axons of granular cells run relative to the axis of the folia?

Answer 12

Parallel.

Question 13

How do axons of Perkinje cells run relative to the axis of the folia?

Answer 13

Peripendicular - straight down (normal, if you will, to the surface) headed toward the deep cerebellar nuclei

Question 14

What’s the destination of Perkinje cell axons? Are the excitatory or inhibitory?

Answer 14

Deep cerebellar nuclei. Inhibitory.

Question 15

What are the 3 functional divisions of the cerebellum?

Answer 15

The vesibulocerebellum, the spinocerebellum, and the cerebrocerebellum.

Question 16

Where do most of the vestibular inputs go in the cerebellum?

Answer 16

The flocculonodular lobe (a.k.a. the vestibulocerebellum)

Question 17

What anatomical regions constitute the spinocerebellum? What information does it receive?

Answer 17

Vermis and adjacent swathes of the hemispheres.

Receives proprioception from spinocerebellar tracts etc.

Question 18

What anatomical regions constitute the cerebrocerebellum? From where does it receive inputs, and how does that info get there?

Answer 18

Lateral parts of the cerebellar hemispheres. Gets info from the cortex (esp. about the intended motion). Cerebral peduncles -> pontine nuclei -> middle cerebellar peduncles -> cerebrocerebellum.

Question 19

What are “deep cerebellar nuclei” to which the vestibulocerebellum sends efferent information? Where are they?

Answer 19

Vestibular nuclei. They’re outside the cerebellum, in the brainstem.

Question 20

What are “deep cerebellar nuclei” to which the spinocerebellum sends efferent information? Where are they? Where do the nuclei send stuff?

Answer 20

Fastigial nuclei - in the vermis -> medial descending systems
Interposed nuclei - in the medial hemispheres -> lateral descending sytems

Question 21

What are “deep cerebellar nuclei” to which the cerebrocerebellum sends efferent information? Where are they? Where do the nuclei send stuff?

Answer 21

Dentate nuclei, at the medial edge of the cerebrocerebellum. Sends info to motor and premotor cortices.

Question 22

Do the dentate nuclei send information directly to the motor and premotor cortices? What specific path is taken?

Answer 22

No, information is relayed through the ventral lateral (VL) nucleus of thalamus. (he also mentioned the ventral anterior (VA) nucleus… but..)

Question 23

How does the somatotopic map look in the cerebellum? Is population encoding more or less important here than in the motor cortex?

Answer 23

Axial musculature is in the vermis, limbs ipsilaterally in the proximal (medial) hemispheres. Population encoding is more important here (it’s even less like a switchboard).

Question 24

Without an intact cerebellum, what happens in a bicep stretch reflex? Does the same thing happen in voluntary movements?

Answer 24

Reflex overshoots resting position -> stretch reflex in opposite direction -> oscillations. Yes, this happens with voluntary movements too.

Question 25

Might you have an easier time karate-chopping through a piece of wood with a lesioned cerebellum? Why or why not?

Answer 25

Probably. Because the cerebellum makes your arm brake before reaching the target location. (Yeah, I’m making this up. For those of you who haven’t fantasized about karate-chopping through things, apparently it’s all about aiming past the target.)

Question 26

If you had to pick between feedforward and feedback, which is more lost in a lesion to the cerebellum?

Answer 26

Feedforward is lost. Intact feedback causes oscillations.

Question 27

Is the cerebrocerebellum involved in cognitive tasks? Is it important for the memory of learned movements?

Answer 27

Yes, and yes.