L18 Cerebellum: Motor Control/Disease

Question 1

Vestibulocerebellum Afferents and Efferents

Answer 1

2 Afferents from Vestibular System=> Flocculonodular Lobe:

• Afferents from Vestibular Nucleus => IPSILATERAL Cerebellum via Inferior Peduncle => FLOCCULUS (Lateral) as Mossy Fiber Inputs
• Direct Input from Vestibular Nerve (ONLY first-order axons w/ direct access to the cerebellar cortex!!) => NODULUS (Center) + VERMIS

Efferents*:

• Minority of Flocculonodular Purkinje Axons project to Fastigial Nucleus => Axial Muscle Control
• Majority project to Vestibular Nucleus via INFERIOR PEDUNCLE (bypassing deep cerebellar nucelli) => Eye Movement Control

Question 2

ONLY first-order axons w/ direct access to the cerebellar cortex?

Answer 2

Flocculonodular Lobe receives direct Input from Vestibular Nerve**
=> NODULUS (Center) + VERMIS

Question 3

Errors of the Vestibulo-Occular Reflex?

Answer 3

Retinal Slip

Question 4

Vestibulo-Ocular Reflex

Answer 4

Question 5

3 Afferent Tracts of the Spinocerebellum

Answer 5

Posterior Spinocerebellar Trac (PSC): Legs and lower trunk

Cuneocerebellar Tract (CC): Arms and upper trunk

Anterior Spinocerebellar Tract

Question 6

Posterior Spinocerebellar Tract (PSC):

• 1a afferents enter the cord and synapse on _____________________
• 2º ascend ipsilaterally and enter the cerebellum by the _____________ Peduncle (Mossy Fibres)
• Information Relayed?

Answer 6

Posterior Spinocerebellar Tract (PSC):

• 1a afferents enter cord and synapse on Clarke’s nucleus.
• 2º ascend ipsilaterally and enter the cerebellum by the INFERIOR PEDUNCLE (Mossy Fibres)
• Relays information about muscle and joint position/movement (Legs and lower trunk) to the cerebellum

Question 7

Cuneocerebellar Tract (CC):

• 1a axons traveling through the ________________synapse in _________________.
• 2º ascend ipsilaterally and enter the cerebellum by the _____________ Peduncle (Mossy Fibres)
• Information Relayed?

Answer 7

Cuneocerebellar Tract (CC):

• 1a axons traveling through the Fasciculus Cuneatus synapse in Accessory Cuneate Nucleus.
• 2º ascend ipsilaterally and enter the cerebellum by the INFERIOR PEDUNCLE (Mossy Fibres)
• Relays information about muscle and joint position/movement (Arms and Upper Trunk) to the cerebellum

Question 8

Anterior Spinocerebellar Tract

• Tract originates in ____________________________
• Fibres cross the cord and ascend in the anterior spinocerebellar tract to the ______________________
• Enter the cerebellum through _____________________ after which they Cross again in _______________

Answer 8

Anterior Spinocerebellar Tract

• Tract originates in the motor region of grey matter
• Fibres cross the cord and ascend in the anterior spinocerebellar tract to the Lower Midbrain
• Enter the cerebellum through SUPERIOR PEDUNCLE after which they Cross again in cerebellum
• While the spinal tract is contralateral, fibers end up on the same side as they originate.

Question 9

In the Spinocerebellum Purkinje axons from_________ synapse in ________________ Nucleus then:

=> Thalamus: _________________ via __________ PEDUNCLE => _______________________________________

=> Brainstem: __________________ and ______________ via INFERIOR _____________________

Gives rise to ___________________ and ____________________ Tracts => strong effects on muscle tone

Answer 9

In the Spinocerebellum Purkinje axons from Vermis synapse in Fastigial Nucleus then:

=> Thalamus: Ventrolateral Nucleus via SUPERIOR PEDUNCLE => IPSILATERAL Motor Cortex

=> Brainstem: Medullary Reticular Formation and Lateral Vestibular Nucleus via INFERIOR PEDUNCLE

Gives rise to Lateral Vestibulospinal and Reticulospinal Tracts => strong effects on muscle tone

Question 10

Cerebrocerebellum receives input from Cortex via ___________________

Purkinje fibers project to_______________ => ____________ PEDUNCLE

Project to _______LATERAL ________________________ of Thalamus.

Answer 10

Cerebrocerebellum receives input from Cortex via Pontine Nuclei

Purkinje fibers project to Dentate Nucleus => SUPERIOR PEDUNCLE

Project to CONTRALATERAL Ventrolateral Nucleus of Thalamus.

Question 11

2 Circuits of the Cerebrocerebellum

• Sensory/Association Cortex: Pathway?
• Motor Cortex and Red Nucleus: Pathway?

Answer 11

• Sensory and Association Cortex: Pontine Nucleus => Cerebrocerebellum => Thalamus => Motor Cortex
• Motor Cortex and Red Nucleus: Inferior Olive (Motor Learning: Climbing fibers change strength of synaptic connection) =>Cerebrocerebellum => Red Nucleus/Motor Cortex

Question 12

Pathway Involved in Motor Learning/Procedural Memory?

Answer 12

Motor Cortex and Red Nucleus: Inferior Olive (Motor Learning: Climbing fibers change strength of synaptic connection) =>Cerebrocerebellum => Red Nucleus/Motor Cortex

Question 13

Various Types of Ataxia?

Answer 13

Question 14

_________________________

□ Wide based gait

□ Uneven steps, lateral movement

□ ___________________ (Error in judgment of the passage of time)

□ Associated with SCA1. Subsequent genes named SCA2, SCA3 etc

□ Many forms are polyglutamine (CAG) repeats (Severity depends on number of repeats)

Answer 14

Spinocerebellar Ataxia

□ Wide based gait

□ Uneven steps, lateral movement

□ Dyschronometria (Error in judgement of the passage of time)

□ Associated with SCA1. Subsequent genes named SCA2, SCA3 etc

□ Many forms are polyglutamine (CAG) repeats (Severity depends on number of repeats)

Question 15

____________________________

□ Intention Tremor

□ Handwriting Abnormalities

□ ______________ (Slurring, Irregular Rhythm)

□ ______________ (Error in judgement of the passage of time)

Answer 15

Cerebrocerebellar Ataxia

□ Intention Tremor

□ Handwriting Abnormalities

□ Dysarthria (Slurring, Irregular Rhythm)

□ Dyschronometria (Error in judgement of the passage of time)

Question 16

____________________

□ Postural Instability

□ Negative _______________ (Uncorrected by visual input- Visual input cannot be integrated)

Answer 16

Vestibulocerebellar Ataxia

□ Postural Instability

□ Negative Romberg’s Test (Uncorrected by visual input- Visual input cannot be integrated)

Question 17

_________________________

□ Wide based gait

□ Uneven steps, lateral movement

□ ___________________ (Error in judgment of the passage of time)

□ Associated with SCA1. Subsequent genes named SCA2, SCA3 etc

□ Many forms are ______________ repeats (Severity depends on number of repeats)

Answer 17

Spinocerebellar Ataxia

□ Wide-based gait

□ Uneven steps, lateral movement

□ Dyschronometria (Error in judgement of the passage of time)

□ Associated with SCA1. Subsequent genes named SCA2, SCA3 etc

□ Many forms are ______________repeats (Severity depends on number of repeats)

Question 18

Purkinje Cell’s function in controlling motion?

Answer 18

Question 19

_______________________: Impairment of movements exibiting a rapid change in motion. Caused by a failure to switch on/off antagonizing muscle groups?

Damage to which part of the Brain is this characteristic of?

Answer 19

Dysdiadochokinesia: Impairment of movements exibiting a rapid change in motion. Caused by a failure to switch on/off antagonizing muscle groups.

Characteristic of damage to LATERAL CEREBELLUM

Question 20

______________________: Difficulty in judging scale

Answer 20

Dysmetria: Difficulty in judging scale:

• Hypermetria: Movements overshoot
• Hypometria: Movements undershoot

Question 21

_________________:

• When lost as an adult is catastrophic
• When lost congenitally, cortex takes over limiting ataxia => better with age

Answer 21

Cerebellar Agenesis:

• When lost as an adult is catastrophic
• When lost congenitally, cortex takes over limiting ataxia => better with age

Question 22

Olivopontocerebellar Atrophy:

□ ___________ (alpha-synuclein abnormalities) and _______ (RARE) forms

□ White matter loss (LOSS OF ______, NOT ______)

□ Purkinje cell loss

□ Loss of _______________ => Parkinsonian Gait occasionally

□ _________ (pain while swallowing) and ________ (Speech disorder)

□ _________ (sudden, unintended, and uncontrollable jerky movements of the arms, legs, and facial muscles)

□ _______ (Slow writing of hands and feet)

□_________________=> Hyperactive tendon reflexes

Answer 22

Olivopontocerebellar Atrophy

□ Sporadic(alpha-synuclein abnormalities) and Inherited (RARE) forms

□ White matter loss (LOSS OF AXON, NOT MYELIN)

□ Purkinje cell loss

□ Loss in substantia nigra => Parkinsonian Gait occasionally

□ Dysphagia (pain while swallowing) and Dysarthria (Speech disorder)

□ Chorea (sudden, unintended, and uncontrollable jerky movements of the arms, legs, and facial muscles)

□ Atheosis (Slow writing of hands and feet)

□ Pyramidal Tract Dysfunction=> Hyperactive tendon reflexes

Question 23

_________________________________________:

□ Results from Thiamine (Vitamin B1) Deficiency => Loss/Shrinkage of _____________

□ Thalamus and ____________ Affected

□ Seen in conjunction with __________________ (anterograde and retrograde amnesia, confabulation)

Symptoms?

Answer 23

Wernicke’s Encephalopathy

□ Results from Thiamine (Vitamin B1) Deficiency => Loss/Shrinkage of Purkinje Cells

• Associated with chronic alcohol abuse (Alchohol inhibits intestinal absorption of thiamine) and HIV

□ Thalamus and Raphe Nucleus Affected

□ Seen in conjunction with Korsakoff’s Syndrome (anterograde and retrograde amnesia, confabulation)

Symptoms:

• Nystagmus (vestibulocerebellum)
• Anisocoria (unequal pupil size)
• Ophthalmoplegia
• Conjugate gaze palsies
• Confusion
• Gait ataxia