cerebellum II

function

motor: involved in equilibrium, muscle tone, postural control, coordination of voluntary movement, timing, motor planning and learning
other: cognitive, emotional, social

spinocerebellum function

vermis and paravermis, ongoing movement
posture, voluntary muscle control, muscle tone, adjustment of limb movement

vestibulocerebellum function

flocculonodular lobe
posture, balance, equilibrium through vestibulospinal and reticulospinal tracts

neocerebellum function

lateral hemispheres, edits movement
planning and control of precise dexterous movement, interval timing, motor learning

ataxia

lack of coordination, normal strength, not associated with hypotonia
paravermal: gait ataxia, lateral: limb ataxia

midline damage

causes postural instability

alcoholism

degeneration of cerebellar cortex tends to start in anterior lobe, causes anterior lobe syndrome

anterior lobe syndrome

LE primarily affected, broad based staggering gait, general incoordination/ataxia
vermal: dysarthria

lateral damage

heavily damaged in most cerebellar lesions, leads to neocerebellar syndrome

neocerebellar syndrome

variable combo of ipsi changes in tone, reflexes, and coordination of voluntary movement, no sensory deficits
hypotonia, hyporeflexia, lack of coordination, limb ataxia, dysmetria, intention tremor, dysdiadochokinesia, decomposition of movement

knee-jerk reflex with cerebellar dysfunction

continued oscillation due to lack of tone to dampen reflex

damage to flocculonodular

affects eye movement, medulloblastomas in 4th ventricle compress nodule
dysequilibrium, staggered walk, wide BOS, falls, no tremors, eye pursuit problems and nystagmus, truncal ataxia, difficulty maintaining balance

superior cerebellar peduncle

afferent: ventral spinocerebellar tracts
efferent: dentate and interposed efferents

middle cerebellar peduncle

pontocerebellar fibers

inferior cerebellar peduncle

juxtarestiform: vestibulocerebellar, fastigial efferents
restiform: dorsal spinocerebellar, cuneocerebellar, rostral spinocerebellar, olivocerebellar, reticulocerebellar tracts

inferior olivary nucleus

communicates with contra cerebellum, “teacher” for cerebellum
input: spinal cord, red nucleus (novelty detector), cortex, cerebellum

deep nuclei

vermis: fastigial nuclei
intermediate zone: interposed nuclei
lateral hemispheres: dentate nuclei
mostly excitatory, except projection to inf olivary nucleus inhibitory

cerebellar cortex

affects ipsi side of body, 3 layered structure
molecular layer superficial: processing
purkinje layer middle: cell bodies of purkinje fibers, inhibitory, only output from cerebellar cortex
granular layer deep

purkinje cells

inhibitory, communicate with deep nuclei and some to vestibular nuclei, only output from cerebellar cortex
each cell only associates with 1 climbing fiber for more selective control

mossy fibers

affect granule cells which become parallel fibers in molecular layer, connects several purkinje cells
send excitatory collaterals to deep nuclei
motor cortex projects to vermis and paravermis, premotor/SI/association project to lateral hemispheres

climbing fibers

axons from contra inferior olivary nucleus and accessory olivary nucleus, excited during novel movements
each synapses on 1-10 purkinje cells, send excitatory collaterals to deep nuclei

cerebellar cortical circuitry

excitatory inputs to deep nuclei modulated by inhibition from purkinje cells

on-beam activation

parallel fibers excite parallel line of purkinje cells and stellate/basket cells, stellate/basket cells inhibit adjacent purkinje cells
activated purkinje fibers inhibit deep nuclei or vestibular nuclei, off-beam purkinje fibers disinhibit deep nuclei

topographical organization

central part of body: vermis
limbs: intermediate zones

vestibulocerebellum afferents/efferents

afferent: ipsi vestibular nuclei and vestibular ganglion projections
efferent: ipsi vestibular nuclei and reticular nuclei

spinocerebellum afferents

primarily spinocerebellar tract inputs, some from pontine nuclei and vestibular afferents

spinocerebellum fastigial efferents

communicates with vermis, postural adjustments, axial musculature, med motor system
bilat vestibular nuclei and reticular formation, contra VA/VL complex, contra cervical cord

spinocerebellum interposed nuclei efferents

communicates with paravermis, limb musculature, lat activation system
influence SC MNs through corticospinal and rubrospinal pathways, firing rate changes during movement - error correction
mainly influences red nucleus, also reticular formation and inf olivary nucleus, VA/VL

cerebrocerebellum afferents

cortical projection via pontine nuclei, inf olivary nucleus

cerebrocerebellum dentate efferents

communicates with lateral hemispheres
VL of thalamus to motor/premotor areas for feedback on motor plan, red nucleus
change firing rate before voluntary movement and some before motor cortex activity

motor learning

process of becoming more skillful in various kinds of movement
some reflexes require cerebellar connection, lesions can impair performance learned movement, role in acquisition of skilled voluntary movement
cerebellum is not essential for engrams (motor plan storage)