T2L5 cerebellum and motor learning Flashcards
role of the cerebellum
- maintenance of balance and posture
- coordination of voluntary movements
- motor learning
- cognitive functions
organisation of motor neurons
s4
motor control of hierarchy
high level:
- association areas of neocortex and basal ganglia
- strategy
mid level:
- motor cortex, cerebellum
- tactics
low level:
- brainstem, spinal chord
- execution
basics of cerebellum function
compares intended movement to movement actually occurring
- voluntary movement
what is actually happening >> cerebellum >> correction signal >> planning, initiation, execution >> what you intend to happen >> cerebellum
s6
anatomy of cerebellum
s9, 11, 13, 15, 17
the 3 cerebellar peduncles:
- superior cerebellar peduncle
- middle cerebellar peduncle
- inferior cerebellar peduncle
functional subunits of cerebellum
vestibulocerebellum
spinocerebellum
- contains 2 maps of the body
cerebrocerebellum
see s13 and s15
4 nuclei of cerebellum
from centre out:
- fastigial nucleus
> medial descending systems > motor execution - interposed nucleus
> lateral descending systems > motor execution - dentate nucleus
> areas 4 and 6 > motor planning - vestibular nucleus (at bottom)
> balance and eye movement
s18 to learn x
cerebellar efferents and afferents
these go both down and up
efferents:
- reticulospinal tract and vestibulospinal tract
- cerebellar efferent neurone (through thalamus to cerebrum
afferents:
- spinocerebellar tracts
- pontocerebellar tract (cerebellum to pontine nuclei)
- corticopontine tract (pontine nuclei to cerebrum)
vestibulocerebellar tracts: - from vestibulocerebellum to vestibular nuclei - then down vestibulospinal tract - and up to extraoculi muscle nuclei s19 and s20 and s21
cerebellar peduncle pathways
not gona learn theses
peduncle
= stalk and see s22
effects of lesions in cerebrocerebellum pathway (4)
- dysmetria - movement not stopped in time- overshoot
- dysnergia - decomposition of complex movement
- dysdiadochokinesia - reduced ability to perform rapidly alering movements eg shaking finger
- dysarthria - incoordination in repiratory/pharyngeal muscles»_space; uneven speech strength and velocity
vestibular-ocular pathway
compensated eye movements from head turn
s26
lesion in vestibulocerebellar pathway
nystagmus - repeated rhythmical oscillations of one or both eyes
this movement minimises ability to focus
lesion in spinocerebellar pathways
gait ataxia- uneven steps
cerebellar circuitry schematic
inputs: - mossy fibres from sc and brainstem - climbing fibres from inf olivary nucleus >> cerebellum >> outputs: - deep cerebellar nuclei to thalami, vestibular nuclei and red nucleus
see s33
4 layers of cerebellar cortex
- molecular layer
- parallel fires - purkinje cell layer
- granule cell layer
- granule cells
- climbing fibres^, mossy fibres^, purkinje cell axonsv
- Golgi cell - white matter
s33,34
feedback loop
- motor cortex and red nucleus generate signals via corticopotinecerebellar tract
- proprioceptive feedback from muscles and joints via the spinocerebellum and the vestibulocerebellum pathways.
- actual response is compared with desired response via the cerebrocerebellum inputs from the supplementary motor cortex and the primary motor cortex to produce error signals.
Mossy fibres = desired signal
climbing fibres = error signal
the alter the purkinje cell output until they are equal
feedforward loop
needed to fast movements as feedback system too slow
Movements that are too fast to be corrected by feedback are executed using predictions of their outcome based on experiences. Crucial for learning new motor skills e.g riding a bicycle
Mossy fibres = desired signal
climbing fibres = error signal
the alter the purkinje cell output until they are equal
s38
Causes of cerebellar dysfunction
- inherited (rare)
- frederichs ataxia - spinocerebellar degeneration - acquired symmetrical ataxia
- alcohol
- drugs
- degenerative (familial)
- immune (paraneoplastic)
worse if the issue is in the white matter tracts - as the cortex has a degree of plasticity
cerebellar vascular anatomy
basilar artery
SCA - superior cerebellar artery
AICA - anterior inferior cerebellar artery
PICA - posterior inferior cerebellar artery