L23: Cerebellum

Question 1

These 3 cerebellar zones are defined based on the source of the strongest inputs. List the 3 zones and their strongest inputs

Answer 1

1) midline (vermis) –> spinocerebellum
2) intermediate (paravermis) –> vestibulocerebellum
3) lateral (lateral) –> cerebrocerebellum

Question 2

The cerebellum is composed of 3 basic elements:

1) cerebellar cortex
2) deep cerebellar nuclei
3) large white matter tracts

List the 6 main types of neurons found in the cerebellum

Answer 2

1 - granule cells
2 - golgi cells
3 - purkinje cells
4 - stellate cells
5 - basket cells
6 - lugaro cells

Question 3

The cerebellum is composed of 3 basic elements:

1) cerebellar cortex
2) deep cerebellar nuclei
3) large white matter tracts

List the 2 types of neurons found in the deep cerebellar nuclei

Answer 3

1) interneurons

2) projection neurons

Question 4

Describe the purkinje cells found in the cerebellum

Answer 4

Purkinje cells send inhibitory projections to the deep cerebellar nuclei, and constitute the sole output of all motor coordination in the cerebellar cortex. they have large dendritic tree and is very unique. these cells only have one output to deep cerebellar fibers, and receive input from climbing fibers from inferior olive in medulla.

Question 5

How do granule cells connect to dendritic trees of purkinje cells?

Answer 5

via parallel fibers

Question 6

What are the 3 different types of non-neuronal cells in the cerebellum?

Answer 6

• radial or “bergmann” glial cells
• bushy astroglia
• oligodendrocytes

Question 7

In broad terms, where do the cerebellum receive their inputs?

Answer 7

• spinal cord
• brain stem
• midbrain
• cerebral cortex (via the pons)

Question 8

Mossy fiber input into the granule cell of cerebellum includes the pontine nuclei receiving info from cortex (corticopontine tract). List 3 other mossy fiber inputs into granule cell of cerebellum.

Answer 8

1 - Reticular formation (arousal)
2 - Spinal cord (position)
3 - Vestibular nuclei (motion)

Question 9

List the 4 amine/cholinergic inputs into granule cell of cerebellum.

Answer 9

1- Raphe (5-HT)
2 - LC (NE)
3 - Ventral tegmental (dopamine)
4 - Pedunculopontine (Ach)

Question 10

What is the major output of cerebellum/.

Answer 10

The predominant output is back to cerebral cortex via thalamus. There are other outputs as well like to inferior olive, to red nucleus, etc.

Question 11

Anatomical data revealed that the cerebellum can be divided into 3 parts.

Answer 11

1. vestibulocerebellum (nodulus & flocculus)
2. spinocerebellum (midline -vermis)
3. cerebrocerebellum (lateral hemispheres)

Question 12

Physiological data revealed more detailed functions of the purkinje cells in terms of the 2 types of action potentials that they generate. Explain

Answer 12

Purkinje cell is the main output cell of the cerebellar cortex. Purkinje cells inhibit deep cerebellar nuclei that powerfully facilitate the thalamus and motor cortex to facilitate movement.

Purkinje fibers fire 2 distinct types of action potentials
1) simple spikes (typical A.P) –> due to action of granule cells (mossy fibers) which will activate purkinje cells via parallel fibers. These simple spikes are related to moment to moment changes in behavior (aka “efference copy” or “reafference)

2) complex spikes (not typical) –> due to unexpected/error signals during spike & after spike, the purkinje fiber is refractory to parallel fiber activation = LONG TERM DEPRESSION. LONG TERM DEPRESSION is the cellular basis for cerebellar learning. Complex spikes are associated with climbing fibers (info from inferior olivary complex to purkinje cells)

Question 13

Define “efference copy” or “reafference” associated with simple spikes produced by purkinje cells when they are activated by granule cells via parallel fibers.

Answer 13

Efference copy –> internal copy of an outflowing, movement producing signal, can serve to enable the brain to predict the effects of an action, impt in enabnling motor adapations

Reafference –> self-initiated motions don’t interfere with perception of constancy

Question 14

What are the triad of symptoms most commonly seen in cerebellar lesions?

Answer 14

1 - asthenia: loss of muscle strength
2 - atonia: loss of muscle tone
3 - ataxia: decomposition of movement; asynergia: difficulty coordinating muscular actions

Question 15

In executing movements, patients with cerebellar lesions can present with what types of symptoms?

Answer 15

• intention tremor
• dysmetria
• dysdiadochokinesia
• nystagmus
• scanning speech

Question 16

Are the functions of the cerebellum somatotopically organized?

Answer 16

yes; regions of cerebellum concerned with sensation and movement of arms, legs, eyes, and face are largely separate from each other.

Question 17

Explain cerebellum’s adaptive modification of behavior

Answer 17

cerebellum can use error signals to adaptively modify commands for movement to optimize outcomes.

Question 18

Is the cerebellum involved in higher cognitive function?

Answer 18

Like the basal ganglia, the cerebellum is involved in higher cognitive function.

Question 19

Does the cerebellum play a role in language?

Answer 19

person with lesion in PICA, but didn’t present with motor problems had language deficits. It shows that cerebellum is active in language.

Question 20

How do you treat cerebellar lesions?

Answer 20

Normally supportive/palliative treatment except in the case of essential tremor in which it’s familial intention tremor, which could be treated with ethanol or barbiturate administration or deep brain stimulation. Ethanol will act as a glutamate antagonist and a GABA agonist so it’s a CNS depressant.

Question 21

What is the effect of chronic alcohol use on cerebellum?

Answer 21

cerebellum shrinks

Question 22

List the 3 cerebellar zones, their cortex region, motor function and cognitive function.

Answer 22

Zone: midline
Cortex region: vermis
motor function: balance, eye movement, reflexes
cognitive function: autonomic, arousal, limbic reg.

Zone: intermediate
Cortex region: paravermal hemisphere
motor function: sensorimotor integration, movement
execution
cognitive function: simple verbal responses to commands

Zone: lateral
cortex region: lateral hemispheres
motor function: preparation & planning of movements, fine motor dexterity, eye movements
cognitive function: verbal association, rule-based learning, working memory, problem solving, monitoring performances.

Question 23

The cell bodies of most mossy fibers entering the cerebellum are located in the: 
 A) cerebral cortex.
 B) cerebellar cortex. 
 C) pons. 
 D) medulla. 
 E) superior colliculus.

Answer 23

C) pons via the pontine nuclei