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Neuroscience 380 > Modulation of Movement by the Cerebellum > Flashcards

Modulation of Movement by the Cerebellum Flashcards

1
Q

What is the primary function of the Cerebellum?

A

To detect the difference (also called “Motor Error”) between an intended movement and the actual movement, and to reduce the error.

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2
Q

Why is the Cerebellum important?

A
  1. Maintenance of balance and posture
  2. Coordination of voluntary movement.
  3. Motor learning
  4. Cognitive function
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3
Q

ANATOMY:

The Cerebellar Hemisphere can be divided into 3 main parts, name them.

A
  1. Cerebrocerebellum
    ROLE: regulation of highly skilled movements; especially planning and execution of complex sequences of movement
  2. Spinocerebellum
    - Paramedian: movements of distal muscles
    - Vermis: movements of proximal muscles
  3. Vestibulocerebellum
    - ROLE: Regulation of movements that maintain posture and equilibrium
    - Vestibulocerebellum is involved in VOR
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4
Q

Connections BETWEEN the cerebellum and nervous system:

Name the Cerebellar peduncles (pathways for fibers going on/out of the cerebellum)

A
  1. Superior: almost entirely effererent. a) neurons originate in deep cerebellar nuclei, b) project to motor nuclei of the thalamus, which in turn relay signals to motor neurons in the primary and premotor cortex
  2. Middle: afferent pathway
    a) neurons originate in the pontine nucleus
  3. Inferior: multiple afferent and efferent pathways
    a) afferent: FROM vestibular nuclei, spinal cord, brainstem, b) efferent: TO vestibular nuclei and reticular formation

Efferent= away from brain, afferent= towards brain (think E for Exit)

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5
Q

ANATOMY:

The Cerebellar Hemisphere can be divided into 3 main parts, name them.

A
  1. Cerebrocerebellum
    ROLE: regulation of highly skilled movements; especially planning and execution of complex sequences of movement
  2. Spinocerebellum
    - Paramedian: movements of distal muscles
    - Vermis: movements of proximal muscles
  3. Vestibulocerebellum
    - ROLE: Regulation of movements that maintain posture and equilibrium
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6
Q

Connections BETWEEN the cerebellum and nervous system:

Name the Cerebellar peduncles (pathways for fibers going on/out of the cerebellum)

A
  1. Superior: almost entirely effererent. a) neurons originate in deep cerebellar nuclei, b) project to motor nuclei of the thalamus, which in turn relay signals to motor neurons in the primary and premotor cortex
  2. Middle: afferent pathway
    a) neurons originate in the pontine nucleus
  3. Inferior: multiple afferent and efferent pathways
    a) afferent: FROM vestibular nuclei, spinal cord, brainstem, b) efferent: TO vestibular nuclei and reticular formation
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7
Q

Projections TO the cerebellum:

Tell me about the Cortex

A
  1. Cortical neurons synapse onto pontine nuclei
  2. Axons of neurons from the pontine nucleus cross midline via the middle cerebellar peduncle- called transverse pontine fibers
  3. Transverse pontine fibers synapse onto neurons in cerebrocerebellum
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8
Q

Projections TO the cerebellum:

Tell me about Sensory Information

A
  1. Proprioceptive info from lower and upper parts of the body is relayed via:
    – Dorsal nucleus of Clark (spinal cord)
    – External cuneate nucleus (medulla)
  2. Proprioceptive info from the face is relayed via:
    Mesencephalic nucleus of the trigeminal complex
  3. Vestibular axons from the VII cranial nerve and vestibular nuclei also project to the vestibulocerebellum

NOTE: Sources of proprioceptive info: labyrinth in the ear, muscle spindles, other mechanoreceptors that monitor the position/motion of the body

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9
Q

Projections TO the Spinocerebellum:

Talk about topography

A

“fractured” topographic map

The vestibular and spinal inputs remain ipsilateral (unlike in cortex)

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10
Q

Projections TO the cerebellum – Inferior Olive:

Talk about the Inferior Olive

A

Input from the inferior olive is important for the learning and memory functions of the cerebellum

  1. The inferior olive (brainstem) receives input from: Cortex (via red nucleus), Reticular Formation, Spinal Cord
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11
Q

Projections FROM the cerebellum:

Name the FOUR Deep Cerebellar Nuclei

A
  1. Dentate nucleus sends info FROM cerebrocerebellum
  2. Interposed nuclei (there are two) and 3. fastigial nucleus: send info FROM spinocerebellum
  3. The vestibulocerebellum projects directly TO the
    vestibular complex in the brainstem.

Destination: upper motor neurons in the brainstem and thalamic nuclei that innervate upper motor neurons in the motor cortex.

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12
Q

Projections FROM the Cerebellum - Cerebrocerebellar:

They project primarily to WHAT and WHERE?

A

Project primarily to the premotor and associational cortices of the frontal lobe, which function in planning voluntary movements.

  1. Dentate nucleus axons exit via superior peduncle
  2. Ascend to contralateral thalamus; collateral to red nucleus
  3. Neurons in thalamus synapse with premotor cortex
  4. Neurons in red nucleus project to inferior olive (feedback loop crucial for adaptive function)
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13
Q

Projections FROM the Cerebellum - Spinocerebellar:

A

Projections target circuits of the Upper Motor Neurons that govern execution of movement

2 pathways: fastigial nuclei and interposed nuclei

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14
Q

Tell me about the Pathway of the Fastigial nuclei

A
  1. Axons exit via inferior peduncle
  2. Project to nuclei of the reticular formation and vestibular complex
  3. Give rise to medial tracts that control axial and proximal limbs
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15
Q

Tell me about the Pathway of the Interposed nuclei

A
  1. Interposed axons exit via superior peduncle

2. Project to thalamic circuits that interact with motor regions

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16
Q

Projections FROM the cerebellum – Superior Colliculus:

The pathway function to control WHAT?

A

controls saccadic eye movement

pathway:

  1. Lateral portions of cerebellar cortex synapse onto dentate and interposed nuclei
  2. Dentate and interposed axons exit via the superior peduncle and cross midline
  3. Axons terminate on upper motor neurons in deep layers of the contralateral superior colliculus

Example: Right cerebellar hemisphere projects to left superior colliculus, which controls saccades toward the right half of the visual field

17
Q

Projections FROM the cerebellum – Vestibulocerebellum:

A

Compensates for linear and rotational accelerations of the head

PATHWAY:

  1. Vestibulocerebellum neurons exit via inferior peduncle
  2. Axons terminate in vestibular complex in the brainstem
18
Q

Circuits WITHIN the cerebellum:

What are purkinje cells?

A

Purkinje Calls are the ultimate destination of afferent pathways in the cerebellum

Purkinje cells are GABAergic!!

19
Q

Circuits WITHIN the Cerebellum- Parallel Fibers:

Talk about the Parallel fibers

A
  1. Mossy fibers: Axons from cells that project into cerebellum (ex., pontine nucleus)
  2. Target of mossy fibers are granule cell layer of cerebellum
  3. Axons of granule cells become parallel fibers
  4. Parallel fibers synapse onto Purkinje cells
20
Q

Circuits WITHIN the Cerebellum- Climbing Fibers:

Talk about Climbing Fibers

A
  1. climbing fibers arise from inferior olive
  2. modulates synapse between parallel fiber and Purkinje cell
  3. provide a training signal that modulates the effectiveness of the parallel fiber connection w the Purkinje cells.
21
Q

Circuits WITHIN the Cerebellum- Climbing Fibers:

Talk about Climbing Fibers

A
  1. climbing fibers arise from inferior olive
  2. modulates synapse between parallel fiber and Purkinje cell
  3. WHY? provide a training signal that modulates the effectiveness of the parallel fiber connection w the Purkinje cells.
22
Q

Circuits WITHIN the cerebellum:

Talk about these circuits

A
  1. Purkinje cells integrate the principle inputs and invert their sign
  2. Mossy fibers and climbing fibers directly synapse onto deep cerebellar nuclei
  3. Golgi cells control the gain of granule cell input through feedback mechanism
  4. Basket cells provide lateral inhibition that may focus spatial distribution.

NOTE: The activity pattern of the deep cerebellar nuclei are sculpted by the descending inhibitory inputs of Purkinje cells which are driven by mossy and climbing fiber projections.

DNTM: Local inhibition controls the flow of information through the cerebellar cortex.

23
Q

Motor Learning in the Cerebellum- LTD vs LTP:

Describe

A

This is the OPPOSITE from most other parts of the brain!

  1. If you stimulate the parallel fiber by itself, you get LTP instead of LTD
  2. If you activate the parallel fiber at the same time as the climbing fiber, you get LTD of parallel fiber input
24
Q

25 Cerebellar Lesions and Disease:

Give general information

A

The hallmark of patients with cerebellar damage is difficulty producing smooth, well-coordinated, multi-jointed movements.

Instead, movements tend to be decomposed into jerky and imprecise actions, referred to as cerebellar ataxia.

NOTE: Woman in China, age 24, without a cerebellum, started walking late (at age 7) and walks unsteadily as an adult and has slurred speech.

25
Q

Modulation of Purkinje cells:

Name and describe

A

STELLATE cells

  • Activated by parallel fibers
  • Inhibit Purkinje cell dendrites

BASKET cells

  • Most powerful source of inhibition
  • Synapse with Purkinje cell bodies

GOLGI cells

  • Activated by parallel fibers
  • Provide inhibitory feedback on granule cells
26
Q

23

Talk about the Contribution of Cerebellum to Learned Changes in the Vestibular Ocular Reflex (with monkey

A

When the animal observes the world through minifying spectacles, the eyes initially move too far with respect to the “slippage” of the visual image on the retina

Over time (several hours), the animal learns to adjust the distance the eyes must move in response to head movements to compensate for the altered size of the visual image

NOTE: VOR: keeps eyes trained on a visual target during head movements

27
Q

24

Talk about the Coordination of Ongoing Movement

A

Neuronal activity in the cerebellum changes continually during course of movement
Both Purkinje cells and cerebellar nuclei are tonically active at rest and change their firing frequency as movement occurs

Look at #24 for difference between at rest and wrist flexion/extension for Purkinje cell and deep nuclear cell

28
Q

25 Cerebellar Lesions and Disease:

What happens with damage to vestibulocerebellum?

A

impairs the ability to stand upright, maintain the direction of gaze, and may decrease muscle tone.

29
Q

25 Cerebellar Lesions and Disease:

What happens with damage to spinocerebellum?

A

difficulty controlling walking movements, performing rapid alternating movements (dysdiadochokinesia), over- or underreaching (dysmetria), and intention tremors.

30
Q

25 Cerebellar Lesions and Disease:

What happens with damage to cerebrocerebellum?

A

impairments in highly skilled learned movements, such as speech or playing an instrument

Neuroscience 380 (13 decks)

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