Task 3 - Cerebellum Flashcards
function cerebellum
- balance (inner ear)
- smooth movements
- if not, it corrects them
- equilibrium (inner ear)
- muscle tone (proprioceptive info used)
- coordination (info from motor areas in cortex)
- motor learning
parts of cerebellum (3)
1) cerebrocerebellum
2) Spinocerebellum
3) Vestibulocerbellum
Cerebrocerebellum
-lateral cerebellar hemisphere
-Input: directly from cortex
-regulation and guidance of highly skilled movements
(planning and execution of complex spatial and temporal sequences of movement)
Spinocerbellum
- median (vermis) and paramedian (more lateral) zone of hemisphere
- input: from spinal cord
-paramedian zone: movement of distal muscles
(info from upper and lower extremities)
-vermis: movement of proximal muscles and certain eye movements
(vermis gets sensory info from trunk head neck)
Vestibulocerebellum
- caudal-inferior lobes ( flocculus and noduclus)
- input: vestibular nuclei in brainstem
- regulation of movement underlying posture equilibrium and vestibulo-ocular reflex (fix eyes on object and move head -> object is fixed, eyes stay fixed) and balance
Pathways (cerebellar peduncles - 3)
1) superior cerebellar peduncle/brachium conjunction
2) middle cerebellar peduncles/brachium pontis
3) Inferior cerebellar peduncles/ restiform body
Superior cerebellar peduncle/ brachium conjunction
- almost entirely efferent pathway
- Location: neurons that give rise to this pathway are in the deep cerebellar nuclei
- Deep Cerebellar Nuclei -> Dorsal Thalamus -> Pre-Motor and Primary Motor
- Deep Cerebellar Nuclei -> Superior Colliculus
middle cerebellar peduncle/ brachium pontis
- affarent, contralateral
- most areas of cortex and superior colliculus -> cell bodies in pontine nuclei of pons -> transverse pontine fibers cross via middle cerebellar peduncle -> cerebellar cortex and deep nuclei
- one of largest pathways in NS
inferior cerebellar peduncle/ restiform body
- smallest but most complex
- affarent pathways: axons from vestibular nuclei (balance, posture) and tegmentum
- efferent: project to vestibular nuclei and reticular formation
affarent vs efferent
affarent -> empfangen, sensorisch
efferent -> agieren , motorisch
4 major deep nuclei in each cerebellar hemisphere
1) Dentate nucleus
2) Two interposed nuclei
3) Fastigal nucleus
Dentate nucleus
- largest nucleus in humans
- receives most input from cerebrocerebellum
- > projects mostly to premotor and association cortices
- > motor planing
Two interposed nuclei
- most input from spinocerebellum
- to motor cortex and brainstem
- > motor execution
Fastigial nucleus
- input from spinocerebellum
- to motor cortex and brainstem
- > motor execution
Cerebrocerebellar pathway
- to dentate nucleus
- decussates at superior cerebellar peduncle
- ascends to thalamus
- then to premotor area
- motor planning
Spinocerebellar pathway starting interposed nucleus
- interposed nucleus
- > project via superior peduncle
- > to thalamus
- > frontal lobe
- motor execution
Spinocerebellum starting at fastigial nucleus
- fastigial nuclei (vermis)
- > inferior peduncle
- > reticular formation (spinal cord)
- > vestibular complex
- > proximate limb muscles
Vestibulocerebellar pathway
- inferior peduncle
- > vestibular complex
- movement of eyes, head, neck
Inputs to cerebellum
- cortex
- spinal cord and medulla
- trigeminal complex
- vestibular nuclei
Input from cortex
- via pontine nuclei (Pons)
- > to cereberocerebellum
- contralateral
spinal cord and medulla input
- to spinocerebellum
- innervated by proprioceptive axons from lower and upper body parts respectively
-proprioceptive: sense of self-movement and body position
Trigeminal complex input
- to spinocerebellum
- proprioceptive signals from the face
input vestibular nuclei and axons from 8th cranial nerve ( inner ear to brain)
-to vestibulocerebellum
-info from ear
-
input from inferior olive and locus coeruleus
- in brainstem
- > learning and memory function
Timing Hypothesis
- cerebellum critical for sensorimotor learning
- generates predictions that are temporally precise
- cortical areas select effectors while cerebellum supplies the precise timing
- lesions are most disruptive to highly practiced movements
- > present greatest need for precise timing
cerebellum contralateral ?
In contrast to the cerebral hemispheres, the left side of the cere- bellum is concerned with movements of the left side of the body, and the right side of the cerebellum is concerned with movements of the right side.
3 layers of cerebellum (from outside to inside)
- molecular level (basket cells, stellate cell, parallel fibers)
- purkinje layer
- granule layer
stellate cells and baskets cells
- activated -> release inhibitory neurotransmitters
- inhibit purkinje cells
neural activity in cerebellum
- cerebellar cortex and deep cerebellar nuclei have spontaneous activity during rest
- during movements both are mainly active during movement changes
cerebellar lesions and diseases - in general
-difficulty in producing smooth and coordinated movements = cerebellar ataxia (disruption of role in correction of errors in ongoing movements)
-damage always on same side as lesion (ipsilateral)
-
alcohol abuse leads to.. in cerebellum…
- degeneration in anterior portion of cerebellar cortex
- affects movements in lower limbs
Damage to vestibulocerebellum
- impairs ability to stand upright and maintain direction of gaze
- disruption of pw to vestibular nuclei -> reduction in muscle tone
Damage to spinocerebellum
- difficulty controlling walking movements and alternating movements
- > hypermetric movements: movements that extend beyond the intended target
Lesions of cerebrocerebellum
-impairments in highly skilled sequences of learned movements (speech, playing a musical instrument)
Article: disruption of state estimation in the human lateral cerebellum (Miall)
what is meant by state estimation process?
- cerebellum crucial for estimation process
- > combines info from efferent motor signals and sensory afferent signals of the motor system
- sensory info reaches brain only after short delay, muscle may already be in motion
- brain must calculate ‘state estimate’ by combining sensory info about last known position of muscle with predictions of its responses to recent movement commands
- > used to accurately plan and control movement
Article: disruption of state estimation in the human lateral cerebellum (Miall)
-method and findings
- using TMS -> interrupting several separate areas in the brain as participants reached a target
- stimulation over cerebellum caused reaching error whereas stimulation to other brain areas did not disrupt reaching direction
- > induced error due to disruption of state estimation process within ipsilateral cerebellum (TSM between go cue and reach-to-target movement)
- reaching movement was inaccurately planned
ataxia and forward model
- people with ataxia have ability to select right movements in right sequences but still lack coordination
- forward model is not intact (not synchronized with ongoing sensory signals)
