Cerebellum and motor learning Flashcards Preview

202: Theme 2, Sensory inputs and motor outputs > Cerebellum and motor learning > Flashcards

Flashcards in Cerebellum and motor learning Deck (30)
1

Cerebellum function [4]

Maintains balance and posture

Co-ordinates voluntary movements
- Compares movement intended to movement actually occuring

Motor learning

Cognition

2

Cerebellar peduncles

Connects the cerebellum to the midbrain.

Three sections:
- Superior: output to the cerebral cortex via thalamic nuclei
- Middle: Connects to the pons via pontine nuclei
- Inferior: Spinocerebellar tract and inferior olive fibres

3

Lobes of the cerebellum

- Anterior
- Posterior
- Flocculonodular

4

Vestibulocerebellum

Functional division of the cerebellum
- Located in the flocculonodular lobe

Function:
- Contains vestibular nuclei involved in balance and eye movements

5

Vestibulocerebellum pathways

Inputs:
- Receives from the semicircular canals of the ear
- Receives afferent fibres from the vestibular nuclei.

Outputs:
- Sends fibres to the vestibular nuclei
- Medial vestibular nuclei leads to vestibulospinal tract
- Lateral vestibular nuclei branches synapse at extra-occular muscle nuclei

6

Spinocerebellum
- Structure
- Function

Composed of the vermis and paravermis- contains two somatotopic maps of the body
- Vermis: Fastigial nucleus----> medial descending systems

- Paravermis: interposed nucleus---> lateral descending systems

Function:
- Motor execution: controls muscle tone and posture

7

Spinocerebellum paths

Inputs:
- Spinocerebellar tracts

Outputs:
- Reticulospinal tract
- Vestibulospinal tract

8

Cerebrocerebellum
- Structure
- Function

Composed of the lateral aspect of the cerebral hemispheres.
- Contains dentate nucleus

Function:
- Dentate nucleus communicates with cortical areas 4+6= motor planning

9

Cerebrocerebellum paths

Input
- Corticopontine tract [primary motor cortex to pontine nuclei]

- Pontocerebellar tract [pontine nuclei to cerebellar cortex]

Output
- Cortex to dentate nuclei
- Dentate nuclei to thalamic nuclei
- Thalamus to primary motor cortex

10

Lobar anatomy of cerebellum

Vermis
- Contains fastigial nucleus

Paravermis
- Contains interposed nucleus

Hemisphere
- Contains dentate nucleus

11

Superior cerebellar peduncle pathways

Exit for outputs to:
- Thalamus [ from dentate nucelus]
- Red nucleus [interposed nucleus]
- Vestibular nuclei [fastigial nucleus]

12

Middle cerebellar peduncle pathways

Contains input from the pontocerebellar tract [from corticopontine tract]

13

Inferior cerebellar peduncle pathways

Allows entry of outputs from:
- Inferior olive tract
- Spinocerebellar tract

14

Dysmetria

Type of ataxia

- Lack of co-ordination
- Overshoot or undershoot for the intended position of: hand, arm, leg, eye.
- Movement is not stopped in time

15

Dsynergia

The inability to conduct complex movements
- Movements are uncoordinated and abrupt

16

Dysdiadochokinesia
- Defintion
- Location of lesion

Type of ataxia

Reduced ability to conduct rapidly alternating movements
- Lesion in cerebellar hemisphere or frontal lobe

17

Intentional tremor

Tremor that arises when trying to perform a visually guided or deliberate movement.

Caused by lesion in vestibular nuclei [i.e in the superior cerebellar peduncle]

18

Dysarthria

Incoordination of the respiratory muscles
- Of the larynx, etc

Causes unclear articulation of speech

19

Vestibular-ocular pathway

Pathway from the vestibular apparatus in the ear to the extra-ocular muscles

1. Vestible---> CN VIII-->vestibular nucleus in the pons

2. Fibres from the vestibular nucleus crosses ----> enters abducens nucleus

3. Abducens nerve from the nuclei---> lateral rectus

4. Fibres from abducens nuclei---> occulomotor nuclei----> medial rectus



20

Nystagmus
- Definiton
- Pathway lesion

Involuntary, rhythmic, oscillations of one or both eyes
- In all directions of views

Prevents eye fixation

Can be caused by lesion of the vestibulocerebellar pathway

21

Spinocerebellar tract lesion effects

Gait ataxia
- Unsteady walking

Hypotonia of the limbs and posture

22

Cerebellar inputs and outputs

Inputs:
- Mossy fibres: from brainstem [pontine, middle cerebellar peduncle] and spinal cord [spinocerebellar tract, inferior cerebellar peduncle]

- Climbing fibres: from inferior olivary nucleus in brainstem.



Outputs, from deep cerebellar nuclei, via superior cerebellar peduncle:
- Thalami
- Vestibular nuclei
- Red nucleus

23

Cerebellar cortex layers

Molecular layer

Purkinje cell layer
- Contains many parallel fibres to each cell

Granule cell layer
- Contains granule cells and golgi cell

White matter layer
- Contains moss fibres and climbing fibres
- Climbing fibre to one purkinje cell but contains many synapses

24

Inputs and outputs of the Purkinje cells

Inputs
- Convergence from parallel fibres [from granule cell] to purkinje dendrites
- One climbing fibre to a purkinje cell that diverges

Output
- To deep cerebellar nuclei

25

Feedback loop - motor learning

1. Desired output

2. Erro signal----> effector muscle---> output

Feedback signal comes from the output---> leads to correction

26

Feedforward loop

Movements too fast to be corrected by feedback
- Done via predictions of pervious outcomes

Advanced information generates desired output ---> fed foward to generate an output

27

Error signals

Derives from sensory information
- Sent via infeiror olivary nucelus ---> climbing fibres

28

Genetic cause of cerebellar dysfunction

Frederich's ataxia

Spinocerebellar degeneration

Ataxia-telengiectasia

Von Hippel Lindau

29

Acquired symmetrical ataxia causes

Alcohol

Metabolic [Low B12, thyroid, ceoliac disease]

Drugs [like phenytoin]

Degenerative disease

Immune

30

Cerebellar motor loop

1. Axons from: Area 4 +6
- Somatosensory cortex
- Posterior parietal cortex
---> Converge into the pontine nuclei

2. Projections of the pontine nuclei enters the cerebellum

3. Projections from cerebellum---> ventral lateral nucleus in thalamus