Cerebellum and Motor Learning Flashcards
what is the cerebellum involved in, within the hierarchal sensorimotor system?
integration and providing fine-motor control
properties of the cerebellum
massive cortical area with only 1 output layer, which is heavily folded
what does the cerebellum exert influence on?
exerts influence on movement via motor and premotor cortex
also connects with brainstem and spinal cord
cells within the cerebellum
Granule cells – 101,000,000,000
Purkinje cells – 15-30,000,000
Golgi, basket, stellate cells – 150-200,000,000
Nuclear cells – 5,000,000
what do purkinje cells receive input from?
receive input from 200,000 parallel fibres and 1 climbing fibre
what does the length and width of the cerebellar cortex reflect?
length - body mass
width - cognitive properties
how many layers does the cerebral cortex have?
molecular layer (near the surface), Purkinje layer, and the granular layer
what are the two inputs into the cerebellar cortex?
- via mossy fibres
- via climbing fibres
input via mossy fibres
connect to granule cells, forming parallel fibres that connect to Purkinje cells
input via climbing fibres
connects to one Purkinje cell with large connections within the energy
what is the only output of the cerebellum?
Purkinje cells – these connect to the deep cerebellar nuclei, which connect via the Thalamus to the rest of the cortex
what are the three sections of deep cerebellar nuclei?
lateral hemisphere
intermediate/paravermal hemisphere
vermal hemisphere
lateral hemisphere
(output into denate nuclei, sending information to cerebro-cerebellum)
intermediate/paravermal hemisphere
(reach interposed nuclei, sending information to spino-cerebellum)
vermal hemisphere
(reaches fastigal nuclei, sending information to spino-cerebellum)
inputs have an ______ effect on the cerebellum and purkinje cells have an ______ effect on the cerebellum
what does this mean?
excitatory effect
inhibitory effect
this means they cancel each other out, and the cerebellar nuclei does not do anythign
what do cortico-cerebellar loops highlight?
the intricate connectivity between the Cerebellum and cortex, suggesting the Cerebellum is involved in more than just motor function
damage to the cerebellum can cause:
hypertremia (overshooting movements)
intention tremors during actions
ataxia (loss of coordination and fine-motor control)
nystagmus (involuntary eye movements affecting balance and gait)
cerebellar affective disorder = impairs executive function, emotion, and personality
wjhat does the “marr-albus” model of motor learning believe?
the cerebellum adapts motor behaviour by synaptic plasticity and LTD
stages of the marr-albus model
- synaptic plasticity between granule cells and Purkinje cells allows it to undergo LTD
- LTD is triggered by simultaneous activity of parallel fibres and climbing fibres via mossy fibres, and error signals via climbing fibres.
- LTD reduces Purkinje cell inhibition of cerebellar nuclei, and disinhibits the direct pathway.
four examples of cerebellar learning
vestibular ocular reflex (VOR)
eye blink conditioning
skill learning
visuomotor recalibration
VOR: what is the cerebellum involved in?
is involved in maintaining stable vision while the head is in motion, by adjusting the VOR gain to prevent retinal slips (blurred vision)
VOR: what happens when retinal slips occur?
when retinal slips occur, they signal an error, and cause the Cerebellum to modulate the amount of gain applied.
If VOR gain is too weak, the retinal slip triggers LTD in Purkinje cells to stabilise vision.
input and output of VOR:
input – vestibular system signal of head motion
output – modulation of direct path to ocular motor neurons
eye blink conditioning: what does the cerebellum associate?
associates the conditioned and unconditioned stimulus, as they respectively reach Purkinje cells via granular and parallel fibres, and climbing fibres
eye blink conditioning: what does simultaneous activation of pathways trigger?
triggers LTD in Purkinje cells, and allows the conditioned response to be elicited by the CS
eye blink conditioning: how does the cerebellum facilitate learning?
facilitates learning by allowing associations to form between sensory cues and motor responses
skill learning: what are complex spikes?
found in purkinje cells, they signal input from climbing fibres and reflect error signals
skill learning: what does monitoring complex spikes allow?
allows us to track the Cerebellum’s response to errors during skill acquisition and learning
visuomotor recalibration: what is the cerebellum crucial for?
crucial for responding to errors, as seen in providing compensatory adjustments to visual inputs when prism glasses are removed.
Learning is blocked by Cerebellar lesions
what does the cerebellar prediction model enable?
enables the comparison of predicted sensory feedback with actual sensory feedback to update motor commands and minimise errors.
what does the predictive mechanism of the cerebellum allow for?
rapid adjustments in movements, even before sensory feedback is received – crucial for fast actions and compensating for slow sensory feedback.
what does feedback control rely on?
relies on sensory feedback to make corrections, leading to slower and jerky movements in patients with impaired Cerebellar function
impairments in anterior lobe of cerebellum
failure in force-field paradigm
impairments in posterior lobe of cerebellum
failure in visuomotor paradigm
what predictive functions does the cerebellum perform?
performs the same predictive functions across several task domains
depends on the area of the cortex this is connected to
what is crucial for anticipating future actions?
predicting sensory outcomes of motor commands
(predictive ability associated with larger cerebellar grey matter volume)
what does cerebellar adaptation improve with?
age
