Cerebellum Flashcards
Reactive postural control
Mvmt is a response to unexpected perturbation.
Anticipatory postural control
Mvmts made to stabilize trunk prior to pre-planned limb movements. 50 msec before prime movers.
Neural systems for reactive/anticipatory movements
Spinal cord (simple stretch responses)
Brainstem (longer latency responses)
Basal Ganglia, Cb
Cortex
Open loop
Mvmt done without any sensory feedback to adjust mvmt in real time.
Faster
Closed loop
Slower mvmts using sensory feedback to adjust while mvmt is ongoing.
Slow ≥ 100 msec duration.
How does Cb fit into the brain’s composition?
10% of volume, 50% of total neurons
How many anatomical parts?
Ant and Post lobes, & flocculonodular lobe
What separates Ant & Post lobes of Cb?
Primary fissure
What does Post-Lat Fissure of Cb separate?
Flocculonodular from Post Lobes
Functional Subdivisions of Cb
Vestibulo-Cb, Spino-Cb, Cerebro-Cb
Vestibulo-Cb
Flocculonodular lobe. Reciprical connections from Vestib system
Spino-Cb
Vermis (rel: trunk) & paravermal area of Ant & Post lobes (rel: limbs). Major afferents from spinal cord.
Cerebro-Cb
Lat Cb hemispheres of Ant & Post lobes. Major afferents from Cerebral Cortex (indirectly).
What are 5 classes of Cb afferents?
1 Vestib System 2 Cerebral Cortex 3 Spinal Cord 4 Visual Afferents 5 Inf Olivary Nucleus
Vestib System Inputs
Ipsilateral. Vestib Nuclei (Medulla) & direct from CN VIII --> Vestibulo-Cb
Cerebral cortex Inputs
Contralateral.
Cortex (mainly motor & sensory areas) –> Synapse in Pontine nuclei (basal pons) –> Pontine axons cross midline and exit via Middle Cb Peduncle –> All parts of Cb
Spinal Cord inputs
Ipsilateral.
From 4 diff SC-Cb tracks via Inf Cb Peduncle.
exit via inferior Cb peduncle –> Vermis & Paravermal hemisphere.
Carries unconscious proprioception info
Visual afferent inputs
Visual cortical areas & Sup Colliculus via Pontine Nuclei
Carries visual proprioceptive info and info re: targets
Inferior Olivary Nucleus inputs
Contralateral.
ION is in Rostral Medulla. Important in Motor Learning. Source of Climbing fibers projections off purkinje cells to all Cb.
Which cells in Cb cortex project to deep Cb nuclei?
Purkinje cells
Which functional system uses Fastigial Nucleus?
Vermal part of Spino-Cb
F –> trunk
Which functional system uses Globose & Emboliform Nucleus?
Paravermal part of Spino-Cb
G&E –> limbs
Which functional system uses Dentate Nucleus?
Lateral Hemishpere (Cerebro-Cb)
What acts as the deep nuclei for Vestib-Cb?
Vestibular nuclei
Efferents of Vestib-Cb
Vestib Nuclei –> vestib sensors in inner ear via CV VIII
What does Vest-Cb coordinate?
Eye mvmt (VOR, saccades) via vestib nuclei projections.
Balance reactions & postural control via vestib-spinal & reticulo-spinal tracts.
Flocculus: smooth pursuit & adaptation of VOR gain.
What is the fxn of spino-Cb division?
dynamic control of ongoing mvmnt
compares intended motor plan with execution to detect error and send info. to correct plan
Describe the efferent pathway to spino-Cb:
efferent copy from motor cerebral cx crosses at pons and exits via middle Cb peduncle
Describe the afferent pathway from spino-Cb
spino-Cb tract project out from DCN through superior Cb peduncle to CONTALATERAL thalamus –> motor/pre-motor cx
Describe the firing of neurons in the spino-Cb:
fire during mvmnts and firing rates tend to change as mvmnt evolves
The vermis is involved in control of:
(F)
trunk mvmnts
saccades
The paravermal hemispheres control
limb mvmnt (G & E)
What is the fxn of cerebro-Cb?
PREDICTIVE CONTROL
- plan/prep mvmnt
- high level internal feedback circuit to regulate cortical mvmnt programs
- evaluation of sensory info for complex tasks
- coordinate skilled and visually guided behavior
What is the major non-motor fxn of cerebro-Cb?
ability to judge passage of time and some language fxns
Afferents to cerebro-Cb are from:
contralateral cerebral cx
motor, premotor, sensory, parietal
The cerebro-Cb uses afferent data to:
schema of the body
(joint position, muscle tension)
in order to anticipate what is needed for mvmnt to occur from that starting state and to update motor programs
Describe the efferent pathway from cerebro-Cb:
(similar to spino-Cb)
CONTRALATERAL motor and premotor cortex via thalamus / superior Cb peduncle
The lateral Cb is involved in coordinating visually guided behavior because:
there is a large visual input to the cerebro-Cb
________ efferents are used as a feedback loop to update motor plants in Cb and cx.
cerebro-Cb
Typical motor impairments associated with Cb lesions:
hypermetria overcorrection decomposition of mvmnt (loss of smooth mvmnt) impaired intersegmental coordination impaired balance (if midline lesion) impaired adaptation
Cb lesions can manifest in impaired…
reactive and anticipatory control in trunk and limb mvmnts
What is a motor set?
requirements to form a planned mvmnt
calculated based on prior experience, current context for mvmnt, and current sensory-motor state (body scheme, posture)
What components of a motor set does the cerebro-Cb coordinate?
timing
amplitude
agonist/antagonist
coordination of limb segments
With damage to cerebro-Cb, what happens to the motor plan?
cannot be calibrated and updated
… leads to ataxia
Ataxia is associated with:
breakdown of mvmnt resulting in decomposition of mvmnt (because no longer have cerebro-Cb to calibrate and update motor plan)
With cerebro-Cb damage, accuracy breaks down (hyper metric), so much more dependent on:
conscious sensory feedback for error correction (snow balls though, bc the error correction is also hyper metric)
What fxnal subdivision acts as “error detector” to modify ongoing mvmnts?
spino-Cb
Spino-Cb lesion can lead to:
hypermetric mvmnts
decomposition of mvmnt (mvmnt breaks down into segments)
Define ataxia:
general word - describes combined influence of Cb dysfxn on gait, posture, patterns of mvmnt
Lesions of Cb produce typical patterns of:
incoordination
impaired balance
decreased muscle tone
What areas of the Cb are responsible for motor learning and adaptation?
all of Cb!!
With removal of flocculus or ION, what is the result?
certain adaptations to certain reflexes cannot be learned
With ION removal, what is the result?
certain conditional reflexes cannot be learned or maintained
All parts of Cb are essential to trial and error adaptation of motor behavior to:
new contexts
adaptation depends on activity.. one motor program is adapted to a new set of task requirements
What is the role of ION in motor learning?
ION is considered the “coach”
(Cb is the “learner)
climbing fiber input facilitates motor learning
With Cb damage, what is the key to rehabilitation?
REPETITION
practice and repeat in order to relearn and adapt
Which area of Cb is particularly important for maintaining static and dynamic balance?
all of Cb … but particularly flocculunodular lobe
helps keep COM over moving BOS using both anticipatory and feedback mechs
The Cb modulates rhythmical output during gait cycle via connections with:
vestibular nuclei via flocculunodular love
these DCN’s activate extensors
What interconnections does the Cb count on for coordinated response for balance rxns and postural control?
vestibular system
reticulospinal system
The Cb adapts locomotor pattern in novel situations especially ones requiring visual guidance by recruiting which fxnal subdivision in particular?
cerebro-Cb
Cb lesion often results in what muscle tone changes?
hypotonia and hyporeflexia
mechanism is thought to involve change in Cb-reticular formation spinal cord circuits
Describe differences you might observe in a pt. with lateral lobe lesion vs. medial lesion:
lateral: more difficulty with accurate limb placement
medial: more difficulty with balance
Define adiodochokinesia:
rapid breakdown of alternating mvmnts
Deficits are seen _______ to the Cb lesion.
ipsilateral
Isolated damage to flocculonodular lobe can lead to:
impaired smooth pursuit
gaze-evoked nystagmus
impaired VOR and VOR cancellation
impaired balance
Isolated vermis damage can lead to:
dec. muscle tone postural tremor, trunk ataxia ataxic gait balance impairment hypermetric saccadic and smooth pursuit eye mvmnts
Isolated vermis damage does NOT affect:
the limbs (no influence on imv tremor or limb ataxia) –> because the vermis is central
Damage to the lateral hemisphere will result in:
limb mvmnt deficits decreased muscle tone limb ataxia hypermetria decomposition of mvmnt
Describe how tremor may present in an individual with midline Cb lesion vs. lateral Cb lesion:
medial: postural tremor
lateral: limb intention tremor
Ataxic gait is characterized by:
dec. angular excursions of multiple joints
varied stride length
abnormal timing of limb segments
reduced walking speed
Abnormal timing of limb segments is associated with:
decomposition of mvmnt
Varied stride length is associated with:
loss of rhythmical control of step cycle
Dec. angular excursions of multiple joints during ataxic gait is an adaptation to:
attempt to dec. DOF and inc. stability
Decomposition of speech is called:
dysarthria
“scanning speech”
Define asthenia:
generalized weakness associated with Cb disorder
Global mvmnt deficits related to Cb dysfxn include:
loss of anticipatory control dymetria inc. reaction time decomposition of mvmnt tremor ataxic gait dysarthria rebound phenomenon asthenia hypotonia adiadochokinesia
With Cb damage, which system remains intact?
conscious sensation intact
What are some common clinical tests for Cb fxn?
finger to nose finger to PT's finger finger to finger alternate nose to finger finger opposition mass grasp pron/sup rebound test tappoing hand or foot heel on shin draw a circle
What are common pathologies that affect the Cb?
tumors stroke acoustic neuromas trauma MS Ataxia (Fredrich's, degenerative, genetic) chronic alcoholism
What vasculature supplied portions of the Cb?
PICA –> post. lobe
AICA –> vest. lobe
SCA –> ant. lobe
Chronic alcoholism especially affects which lobe?
anterior
Considerations for effective intervention planning with Cb damage?
capacity for motor learning
capacity for adaptation for task modification
adaptation to new environmental contexts
coordination of agonist/antagonist pairing for multi-limb mvmnt
