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Neurophysiology > Cerebellum > Flashcards

Cerebellum Flashcards

1
Q

Sum up the cerebellum’s role in one sentence

A

Coordination, calibration, modulation, planning, learning and automating of skilled movements

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2
Q

How does the cerebellum calibrate movement

A

Compares motor command (cortex) with performance feedback (ascending proprioceptor/sensory input) to correct erorrs and make movement more successful

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3
Q

What are the 3 anatomical divisions of the cerebellum

A

Cerebrocerebellum, spinocerebellum, vestibulocerebellum

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4
Q

Which deep output nuclei does the spinocerebellum project to

A

Vermis -> Fastigial

Paravermis -> Interposed nuclei

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5
Q

Which deep output nuclei does the cerebrocerebellum project to

A

Dentate nucleus

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6
Q

What are the deep output nuclei of the cerebellum

A

Fastigial, interposed, dentate

Inside -> outside

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7
Q

What are the 3 major cerebellar tracts

A

Superior peduncle, middle peduncle, inferior peduncle

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8
Q

What is the superior penduncle

A

OUTPUT to thalamus and brainstem, comprises most output

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9
Q

What is the middle peduncle

A

INPUT from pons

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10
Q

What is the inferior peduncle

A

INPUT from vestibular nuclei, spine and inferior olive

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11
Q

How is the cerebellum unique to other motor areas in the brain in terms of how it works with the body

A

Works ipsilaterally with the body

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12
Q

What are the outer big sections of the cerebellum called

A

Lateral hemispheres

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13
Q

What other nuclei is important that’s not the deep nuclei

A

Vestibulo-cerebellum projects to the vestibular nuclei in the brainstem

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14
Q

What is the inner big section of the cerbellum comprised of the vermis and paravermis

A

Medial hemisphere

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15
Q

Where are each of the functional divisions of the cerebellum located

A

Spinocerebellum- medial hemisphere
Cerebrocerebellum- lateral hemispheres
Vestibulocerebellum- flocculonodular lobe

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16
Q

Input to the vestibulocerebellum

A

Direct sensory input from semicircular canals and otolith organs
Vestibular nuclei
Visual input from SC and visual cortex via the pons

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17
Q

Output from the vestibulocerebellum

A

Fastigial deep nucleus
Ocular motor nuclei
Medial/lateral vestibular nuclei -> Medial/lateral vestibulospinal tracts to neck and back muscles

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18
Q

Vestibulocerebellum functions

A

Balance and posture
Orientation of head and body
Eye movements
Vestibulo-ocular reflex

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19
Q

What is the vestibulo-ocular reflex

A

Maintains foveation of an object during head movements

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20
Q

Input to the cerebrocerebellum

A

Cortex -> pons -> dentate nucleus

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21
Q

Output from the cerebrocerebellum

A

From dentate nucleus-
Motor control areas and PFC via the ventrolateral thalamus
Red nucleus -> inferior olivary nucleus -> cerebellum

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22
Q

Functions of the cerebrocerebellum

A

Planning/timing/initiating precise movement
Feedback circuit to regulate cortical motor programs
Motor learning
Cognitive function

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23
Q

What is the function of the red nucleus -ION- cerebellar loop formed from from the cerebrocerbelleum

A

The red nucleus also receives input from premotor areas- loop may involve motor learning

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24
Q

How may the cerebrocerebellum be involved in cogntiive function

A

Dentate nucleus appears important in processing sensory info for tasks requiring spatial and temporal judgements

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25
Q

Input to the spinocerebellum

A

Instruction from sensory and motor cortex
Dorsal and ventral spinocerebellar tracts- neck. trunk, limbs
Inferior olivary nuclei

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26
Q

How does the spinocerebellum receive direct vs indirect input from the dorsal and ventral spinocerebellar tracts

A

Direct input from interneurons in the spinal grey matter -> mossy fibres
Indirect input via reticular formation nuclei

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27
Q

Output from the spinocerebellum- vermis

A

Via fastigial nuclei

Ventromedial brainstem descending systems- vestibulo, reticulo, and cortico-spina tracts VIA a thalamocortical relay

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28
Q

Output from the spinocerebellum- paravermis

A

Via interposed nuclei

Lateral descending systems- rubro and corticospinal tracts

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29
Q

Spinocerebellum functions

A

Control of axial and limb musculature for posture and locomotion, modulates descending motor systems through thalamocortical relay, online movement-correction, feed-forward control

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30
Q

How does the spinocerebellum do feedforward control

A

Can elaborate proprioceptive input to anticipate future body position during movement

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31
Q

What region of the spinocerebellum is involved in controlling eye movement together with the vertibulocerebellum

A

Vermis- controls saccades and smooth-pursuit eye movements

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32
Q

What info does the spinocerebellum receive from the dorsal vs ventral spinocerebellar tracts

A

Dorsal- sensory feedback from muscles following movement

Ventral- info about spinal motor neuron activity

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33
Q

How does the spinocerebellum do online correction of movement

A

Compares planned movement (from ventral spinocerebellar tract) with actual movement (dorsal cerebellar tract) to allow correction

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34
Q

What suggests there is a cognitive role for the cerebellum

A

Prefrontal connections
Expansion of cerebellar hemispheres evolved in conjunction with cerebral expansion
Cerebellar cognitive affective syndrome

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35
Q

Symptoms of cerebellar cognitive affective syndrome

A

Deficits in language, visual spatial and executive functions, disorganised through

36
Q

What is the cerebellar outer cortex made up of

A

100 thousand million neurons (1/2 all neurons in the brain) in highly ordered repeating P-cell modules

37
Q

What cells provide input to the P-cell modules

A

Mossy fibre input from all regions involved eg vestib, spinal, pons
Climbing fibre input from IO

38
Q

What are the 3 layers of the P-cell modules

A

Molecular layer, Purkinje cell layer, inner granule cell layer (OUT->IN)

39
Q

What cells are in the molecular layer of the P cell module

A

Purkinje cell dendrites, granule cell parallel fibres, climbing fibres, various interneurons

40
Q

What cells are in the Purkinje cell layer of the P cell module

A

Purkinje cells (principal output to deep nuclei)

41
Q

What cells are in the inner granule cell layer of the P cell module

A

Granule cells, mossy fibre inputs, Golgi interneurons

42
Q

Where are the cell bodies of mossy fibres

A

Spinal cord, brain stem

43
Q

What synapses do mossy fibres form

A

EXCITATORY synapses on granule cell dendrites in the granular layer
EXCITATORY direct synapses with target neurons in deep output nuclei

44
Q

What is the neurotransmitter identity of granule cell parallel fibres in the outer molecular layer

A

Glutamatergic (EXCITATORY)

45
Q

What input does each Purkinje cell receive from granule parallel fibres

A

Input from 200,000 parallel fibres firing at 50-100Hz

Input from ~200 summates

46
Q

What sort of firing does input from summated granule parallel fibres elicit in Purkinje cells

A

Simple Na/K spikes (20-50Hz)

47
Q

What modulates the frequency of simple spikes in Purkinje cells (caused by parallel granule fibres)

A

Sensory and motor inputs eg muscle spindles, visual input

48
Q

How are P specific in their firing

A

P cells are tuned to particular source/type of input

Project topographically onto the body map in the deep output nuclei

49
Q

What output do Purkinje cells provide

A

Inhibitory output to deep output nuclei

50
Q

What does Purkinje inhibitory output to the deep output nuclei allow

A

Online calibration and optimisation of movement by correcting motor errors

51
Q

What is the result of the long trajectory of granule cell parallel fibres

A

Allows them to contact many P cells that project along the anterior-posterior body axis in the deep output nuclei map, allowing coordinated multi-muscle movement

52
Q

What info does the inferior olivary nuclei receive

A

Info from the spinal cord and cerebral cortex

53
Q

What synapses do the climbing fibres form

A

Each climbing fibre winds through the dendritic tree of a Purkinje fibre, making around 300 synapses
1:1 ratio
Climbing fibre collaterals also excite the deep nuclei

54
Q

What firing does APs from climbing fibres elicit in Purkinje fibres

A

A single AP from CFs (1-10Hz) generates a large EPSP, causing prolonged Ca2+ dependent complex spike in Purkinje fibres

55
Q

What is the result of prolonged Ca2+ dependent complex spikes caused by climbing fibre input in P cells

A

LTD of parallel fibre- Purkinje cell synapses, reducing the efficacy of mossy fibre inputs

56
Q

In what way do climbing fibres map onto Purkinje fibres

A

Climbing fibre terminals are arranged in a way that maintains IO topography on Purkinje fibres

57
Q

What is the role of climbing fibres

A

Report ‘error’ to P cells (discrepancy between cerebellar motor command and sensory detection), and ‘teach’ Purkinje cells which parallel fibres they should become less responsive to

58
Q

How many granule cels are in the granule cell layer

A

10 ^11

59
Q

How many Purkinje cells are in the Purkinje cell layer

A

3 X 10^7

60
Q

How many complex spikes does each sensory stimuli/movement generate in P cells

A

Only 1-2 complex spikes

61
Q

What do climbing fibres allow BIG PICTURE

A

Cerebellum-dependent motor learning, recalibration and optimisation of movement

62
Q

What 3 types of interneurons exist in the P modules

A

Basket cells, stellate cells, golgi cells

63
Q

What input do cerebellar interneurons receive

A

Excitatory granule cell parallel fibre input

64
Q

What do basket interneurons do

A

Project to neighbouring P cells forming a basket, inhibiting activity in ‘off-beam’ P cells
LATERAL INHIBITION

65
Q

What do stellate interneurons do

A

Short-range within-beam inhibition of P cells. regulatory effect

66
Q

What do Golgi interneurons do

A

Project back to granule cells and provide feedback inhibition, curtailing duration of excitement of GCs by mossy fibres

67
Q

What is hypotonia

A

Diminished resistant to passive limb displacements

68
Q

What is atasia

A

Loss of ability to maintain steady limb/body postrue across multiple joints

69
Q

What is abasia

A

Loss of ability to maintain upright stance against gravity, often moving their legs irregularly and falling

70
Q

What is ataxia

A

Abnormal execution of multi-jointed movements, lack of coordination

71
Q

What characterises cerebellar disorders

A

Loss of automatic, unconscious nature of most movements, especially consisting of sequential movements

72
Q

How do cerebellar lesinos affect the vestibular-ocular reflex

A

Inability to learn to reverse the VOR is caused by vestibulocerebellar lesions

73
Q

What happens to the frequency of simple and complex spikes when first learning a new task

A

Learning a new task- increased frequency of complex spikes, gradual decrease in simple spikes

74
Q

What happens to the frequency of simple and complex spikes when a task has been learned

A

Frequency of complex spikes returns to control, frequency of simple spikes remains decreased

75
Q

What is dysmetria

A

Poor accuracy of movement

76
Q

What is tremor

A

Low frequency high amplitude oscillations of a limb as it approaches target, overshooting/overcompensated

77
Q

What is dysdiadochokinesis

A

Poor rapid alternating movements

78
Q

What is postural ataxia

A

Incoordination of axial muscles, postural instability, staggering wide-based ataxic gait

79
Q

What do vestibulocerebellar lesions cause

A

Poor balance, nystagmus (eye drift and jump)

80
Q

What do spinocerebellar lesions cause

A

Lesions of medial zone- problems standing or walking

Lesions of intermediate zone- poor accuracy, action tremor (3-5Hz)

81
Q

What do cerebrocerebellar lesions cause

A

Disrupts multijoint movements eg reaching and grasping objects

82
Q

What does firing of climbing fibres correspond with

A

When stimulated, they fire single APs in temporal relation with specific sensory events- suggests they signal important events

83
Q

What does firing of Purkinje fibres

A

Fire at up to several hundred spikes a sec during active eye, arm and face movements, due to lots of sensory info converging on the granule cells
Mossy fibre system thus encodes magnitude and direction of peripheral stimuli

84
Q

Recurrent loops- thalamocortical loop?

A

Cerebral cortex->pons->lateral cerebellum->thalamus->cerebral cortex

85
Q

Recurretnt loops- self-regulating loops

A

Deep cerebellar nuclei project GABAergic inhibitory neurons to the inferior olive, allowing the cerebellum to regulate its climbing fibre input

86
Q

What are interal models

A

Interal models of the limbs within the cerebellum automatically take account of limb structure eg a dynamic arm model can convert a desired endpoint into a sequnce of commnds
Can be modulated

Neurophysiology (23 decks)

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