Cerebellum and Motor Learning wk9

Question 1

what is the cerebellum involved in, within the hierarchal sensorimotor system?

Answer 1

constantly processing sensory input from the all senses in the world to update our motor system about movements to perform

in charge of integration and providing fine-motor control

Question 2

properties of the cerebellum

Answer 2

massive cortical area with only 1 output layer, which is heavily folded/densely packed

Question 3

what does the cerebellum exert influence on?

Answer 3

exerts influence on movement via motor and premotor cortex

also connects with brainstem and spinal cord

Question 4

cells within the cerebellum

Answer 4

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

Question 5

Flattening the cortical sheet of the cerebellum

Answer 5

• wider surface area within humans as it plays a greater role in motor control
• width much narrower in humans due to increase of cognitive functioning demands

Question 6

what do purkinje cells receive input from?

Answer 6

receive sensory input from 200,000 parallel fibres and 1 climbing fibre

Question 7

what does the length and width of the cerebellar cortex reflect?

Answer 7

length - body mass
width - cognitive properties

Question 8

how many layers does the cerebral cortex have?

Answer 8

molecular layer (near the surface), Purkinje layer, and the granular layer (last)

Question 9

The molecular layer

Answer 9

Made up of the dendrites of the Purkinje cells (where sensory info is received , processed by Purkinje cells)

Question 10

The granular layer

Answer 10

made up of Golgi cells, their dendrites come up and interact with Purkinje cells that send sending info about sensation

Question 11

step 1. input via mossy fibres

Answer 11

where sensory info comes in

connect to granule cells, forming parallel fibres that connect to Purkinje cells to signal sensory info

Question 12

step 2. Purkinje cells

Answer 12

where motor learning mainly takes place

axons of the purkinje cells send inhibatoey output away from the cerebllum to the motor parts of the cortex

Question 13

step 3. climbing fibres

Answer 13

connects to one Purkinje cell with large connections

sends info about the current state of the body, as an indication of what movements we want to perform

Question 14

step 4. The cerebellum

Answer 14

compares info from the senses and a prediction of where our hand needs to be in space

If the two match up= successful movement

mismatch= error in prediction-> learning + adaptation of output to motor cortex

so, we compare the sensory consequences of our actions compared with a prediction of the movement we want to perform

Question 15

How is output of the cerebellum to rest of the brain achieved

Answer 15

via deep cerebellar nuclei which sends output to motor structures of the cerebral cortex

allows for updates and smooth movement OR adaptation

Question 16

what are the three sections of deep cerebellar nuclei?

Answer 16

lateral hemisphere

intermediate/paravermal hemisphere

vermal hemisphere

Question 17

inputs have an ______ effect on the cerebellum and purkinje cells have an ______ effect on the cerebellum

what does this mean?

Answer 17

excitatory effect
inhibitory effect

this means they cancel each other out, and the cerebellar nuclei does not do anythign

Question 18

what do cortico-cerebellar loops highlight?

Answer 18

the intricate connectivity between the Cerebellum and cortex, suggesting the Cerebellum is involved in more than just motor function, receiving different sources of sensory input

allows for anticipation of how we will move in the future

Question 19

damage to the cerebellum can cause:

Answer 19

hypertremia (overshooting movements) - fails finger-to-nose test

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

Question 20

what does the “marr-albus” model of motor learning believe?

Answer 20

the cerebellum adapts motor behaviour by synaptic plasticity and LTD

Question 21

what info arrives at purkinje cells according to the marr-albus model

Answer 21

both motor (intended movement/perdition) and sensory info to facilitate motor learning

Question 22

stages of the marr-albus model

Answer 22

1. synaptic plasticity between granule cells (parallel fibres) and Purkinje cells allows it to undergo LTD
2. LTD is triggered by simultaneous activity of parallel fibres and climbing fibres (associative learning) via mossy fibres, and its error signals
3. LTD reduces Purkinje cell inhibition of cerebellar nuclei, and disinhibits the direct pathway.
4. drives cerebellum to modulate motor output so next time an accurate movement will be made
    

Question 23

four examples of cerebellar learning

Answer 23

vestibular ocular reflex (VOR)
eye blink conditioning
skill learning
visuomotor recalibration

Question 24

VOR: what is the cerebellum involved in?

Answer 24

is involved in maintaining stable vision while the head is in motion, by adjusting the VOR gain to prevent retinal slips (blurred vision occuring when eyes dont move in proportion to head motion)

Question 25

VOR: what happens when retinal slips occur?

Answer 25

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 + learn to control eyes better

Question 26

input and output of VOR:

Answer 26

input – vestibular system signal of head motion output – modulation of direct path to ocular motor neurons

Question 27

eye blink conditioning: what does the cerebellum associate?

Answer 27

associates the conditioned and unconditioned stimulus , as they respectively reach Purkinje cells via granular and parallel fibres (so learning of association takes place)

Question 28

eye blink conditioning: what does simultaneous activation of pathways trigger?

Answer 28

triggers LTD in Purkinje cells, and allows the conditioned response to be elicited by the CS output= blink in response to touch instead of air puff

Question 29

eye blink conditioning: how does the cerebellum facilitate learning?

Answer 29

facilitates learning by allowing associations to form between sensory cues and motor responses

Question 30

skill learning: what are complex spikes?

Answer 30

found in purkinje cells, they signal input from climbing fibres and reflect error signals when adapted, they spike in activity to the onset and offset of movement

Question 31

skill learning: what does monitoring complex spikes allow?

Answer 31

allows us to neurologically track the Cerebellum’s response to errors during skill acquisition and learning

Question 32

visuomotor recalibration: what is the cerebellum crucial for?

Answer 32

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

Question 33

what does the cerebellar prediction model enable?

Answer 33

enables the comparison of predicted sensory feedback with actual sensory feedback to update motor commands and minimise errors.

Question 34

what does the predictive mechanism of the cerebellum allow for?

Answer 34

rapid adjustments in movements, even before sensory feedback is received – crucial for fast actions and compensating for slow sensory feedback.

Question 35

what does feedback control rely on?

Answer 35

relies on sensory feedback to make corrections, leading to slower and jerky movements in patients with impaired Cerebellar function as they cannot make predictions or adapt from discrepancies

Question 36

What type of error discrepencies is the cerebellum responsible for adapting to

Answer 36

both visual motor (visuals dont match up to movement ) and forcefield (hands dont match up to movement ) errors cerebellum processes many types of sensory input so can do both depends on the area of the cortex this is connected to

Question 37

impairments in anterior lobe of cerebellum

Answer 37

failure in force-field paradigm

Question 38

impairments in posterior lobe of cerebellum

Answer 38

failure in visuomotor paradigm

Question 39

What is state estimation

Answer 39

when the cerebellum has to monitor the state of the body in space throughout the entire movement (e.g. how fast you're moving , angle of joints ) to make judgements

Question 40

cerebellum without sensory input

Answer 40

cerebellum still able to learn without sensory input , just anticipating is good enough

Question 41

what is co ordination/tracking dependent on

Answer 41

the cerebellum & its predictive knowledge of the outcome of intended actions essential in eye-hand co ordination

Question 42

why is predicting sensory outcomes of motor commands essential

Answer 42

- for fast movements - when sensory feedback is poor or not available - for prediction (predictive ability associated with larger cerebellar grey matter volume)

Question 43

what does cerebellar adaptation improve with?

Answer 43

age

Question 44

Cerebellum outside motor control

Answer 44

also projects to prefrontal cortical regions which are associated to different cognitive functions e.g. language prediction

Question 45

How can the predictive ability of our cerebellum be enhanced

Answer 45

through TDS though results are inconsistent TDS only effective in difficult tasks where there aren't enough cognitive resources