Cerebellum & Motor Learning Flashcards
Does the cerebellum interpret information?
No - rather takes information in and moderates it to allow smooth muscle movements
Does the cerebellum initiate motor activity?
No - just alters the sensory messages for smooth movement
Does the cerebellum include higher function?
Yes - is some higher function in the cerebellum - especially in relation to motor learning.
How does the cerebellum impact motor activity?
Provides for
- synergy of movement (smoothness)
- maintenance of posture
- maintenance of muscle tone
BUT does not initiate motor activity
How is the cerebellum connected to the brainstem?
Via three peduncles
What are the names of the cerebral peduncles?
Superior cerebellar peduncle
Middle cerebellar peduncle
Inferior cerebellar peduncle
What are the peduncles made of and what do they do?
Made of WM tracts
Take information in and out of the cerebellum
What is the inferior peduncle primarily involved with?
Information entering the cerebellum from the spinal cord directly
What is the role of the middle cerebellar peduncle?
Takes transverse fibres into and out of the brainstem from the cerebellum
What is the role of the superior cerebellar peduncle?
Mainly involved with messages to and from the cerebral cortex directly
How many hemispheres does the cerebellum have?
Two
What are the two hemispheres of the cerebellum connected by?
Vermis
What are the lobes of the cerebellum?
Anterior lobe
Posterior lobe
Flocculonodular lobe
How is the cerebellum divided functionally?
Divided into functioning modules:
Vesibulocerebellum (flocculonodular lobe)
Spinocerebellum (paravermal and vermis)
Pontocerebellum
What are the names of the deep cerebellar nuclei?
Dentate nucleus
Fastigial nucleus
Interposed nucleus
What is the pontocerebellum also known as?
Cerebrocerebellum
Which deep nuclei is found in the vermis?
Fastigial nucleus
Which deep nucleus is found in the paravermal area?
Interposed nuclei
Which deep nucleus is found in the pontocerebellum?
Dentate nucleus
What is the outer layer of the cerebellum called?
Cerebellar cortex
Where does information for the cerebellum come from?
Direct from spinal cord (spinocerebellar tracts)
From brainstem nuclei
All input to the cerebellum is excitatory or inhibitory?
Excitatory
Which bits of the body send information to the cerebellum?
Muscle spindles
Golgi tendon organs
Cutaneous receptors
The cerebellum affects the ipsilateral or contralateral side of the body?
Ipsilateral
What are the three divisions of the spinocerebellar tract?
Dorsal spinocerebellar tract
Cuneocerebellar spinocerebellar tract
Ventral spinocerebellar tract
Are the spinocerebellar tracts quick or slow?
Quick - only 2 connections in this - to allow for fast moderation of movement
What does the dorsal spinocerebellar tract coordinate?
Individual leg muscles
What does the cuneocerebellar tract coordinate?
Individual arm muscles
What does the ventral spinocerebellar tract coordinate?
The whole limb = synergy of movement
Name an important brainstem nucleus which sends information directly to the cerebellum.
Inferior olivary nucleus
Which brainstem nucleus inputs info from the vestibular system to the cerebellum?
Vestibular nuceli
Which brainstem nucleus modulates spinal reflexes (esp extensors)?
Reticular formation
Which brainstem nucleus relays information to the cerebellum from the cerebral cortex from the inferior olivary nucleus?
Red nucleus
What is the function of the inferior olivary nucleus?
Integrates signals from spinal cord and cerebral cortex and passes to the cerebellum
Which brainstem nuclei connects the cerebral cortex to the cerebellum via transverse fibres?
Deep pontine nuclei
Does the cerebral cortex coordinate with the ipsilateral cerebellar hemisphere or the contralateral?
Contralateral
Which deep nuclei coordinates fibres from the inferior and superior colliculus to provide auditory and visual input to the cerebellum (via deep pontine nuclei)?
Tectum
How does information enter and leave the cerebellum?
Information enters the cerebellum (either from the spinal cord or the brainstem nuclei).
It travels to the relevant area of the cerebellum (vestibulocerebellum, spinocerebellum or pontocerebellum).
Then travels to the cerebellar cortex of that area.
Then to the deep nuclei of the cerebellum (as inhibitory message).
The exits the cerebellum from the deep nuclei as excitatory message.
What functions are the following deep nuclei involved in controlling?
- Fastigial & Interposed nuclei
- Dentate nuclei
- Vestibular nuclei
Fastigial & interposed = motor execution
Dentate = motor planning
Vestibular = balance and eye movements
What is the pathway for coordinating balance and eye movements via the vestibulocerebellum?
Information enters via the vestibular nerve and travels to the vestibular nuclei.
Messages then travel to the flocculonodular node. Modification occurs.
Messages then travel back to the vestibular nuclei (as inhibitory).
Messages leave the vestibular nuclei & cerebellum as excitatory messages.
Which parts of the brain are involved in eye movement, control, balance & posture?
Vestibular nuclei, visual cortex, superior colliculus, reticular formation.
What is the pathway for motor control via the spinocerebellum?
Information enters from spinocerebellar tracts and brainstem nuclei.
Travels to cerebellar cortex
Travels to deep nuclei - fastigial (vermis) or interposed (paravermis) as inhibitory message
Leaves the deep nuclei as excitatory information to travel down descending tracts
OR
To the inferior olivary nucleus (to red nucleus to cerebral cortex = motor control and learning).
What is the pathway for information entering and leaving the pontocerebellum?
Messages arrive from the cerebral cortex via corticopontine tract.
Messages synapse with the deep pontine nuclei - then travel in transverse bundles to the pontocerebellum.
Messages then travel to the dentate nucleus (as inhibitory messages)
Messages leave as excitatory - travel to thalamus (brain) and then back to cerebral cortex to modulate activity
What is the organisation of the cerebellum called?
Fractionated somatotopy =. topographical localisation
Which parts of the body are represented
- medially
- laterally anterior (paravermis)
- laterally posterior (paravermis)?
Medially = axial muscles
Laterally anterior = legs
Laterally posterior = arms
Why is the organisation of the cerebellum important for pathology?
The body parts are represented in several different locations - means that if you damage a bit of the cerebellar cortex, you are less likely to have a problem with that region than if you damaged the cerebral cortex.
What happens if you damage a deep nuclei of the cerebellum?
Likely to be very symptomatic as that is where all the messages of the cerebellum gather to exit.
All input to the cerebellum is ?
Excitatory
All output from the cerebellar cortex to the deep cerebellar nuclei is?
Inhibitory
All output from the deep cerebellar nuclei is ?
Excitatory
All messages in the cerebellum are coded by ?
Excitation and inhibition
What are the two types of fibre that input information to the cerebellum?
Mossy fibres
Climbing fibres
What is the cerebellum architecture designed to do?
Influence and coordinate lots of different parts of the body at the same time
What are the three layers of the cerebellar cortex?
Molecular layer
Purkinje layer
Granule cell layer
Which two cells are mainly found in the granule cell layer of the cerebellum?
Which is the most common?
Granule cell - most common
Golgi cell
What do granule cells receive information from?
Mossy fibre afferents
Where do axons of the granule cells ascend to?
Surface of cerebellar cortex
Where do axons of the granule cells ascend to?
Surface of cerebellar cortex
In which layer do the granule cell axons bifurcate into parallel fibres?
Molecular layer
How do messages enter the cerebellum?
Enter via mossy fibres - some go straight to deep nuclei, others go to granule cell layer and connect with granule cells. Granule cell axons then travel to the molecular layer, bifurcate into parallel fibres and connect to purkinje cells.
What do the parallel fibres of the granule cell axons synapse with?
Do granule cells pass strong or weak messages onto them?
Purkinje cells in the cerebellar cortex.
Send weak messages
Which are the only cells that output information from the cerebellar cortex? Where do they send messages to?
Purkinje cells - send messages to the deep cerebellar nuclei
Are Golgi cells inhibitory or excitatory? Which NT do they use?
Are inhibitory GABA-ergic cells
What do golgi cells do? Where do they receive their messages from?
Receive messages from parallel fibres + mossy fibres.
They inhibit granular cells = negative feedback
Which cell is found in the purkinje cell layer?
Purkinje cells
Where do axons of purkinje cells go?
Deep cerebellar nuclei
Which is the only cell that produces output from the cerebellum?
Purkinje cells
What type of messages do Purkinje cells do - excitatory or inhibitory?
Inhibitory
What is found in the molecular layer of the cerebellar cortex?
Dendrites of Purkinje cells
Terminal branches of climbing fibres
Parallel fibres of granule cells
2 x interneurons (basket cells and stellate cells)
What are the two types of interneurons found in the cerebellar cortex? What do they do?
Basket cells
Stellate cells
They sharpen the focus of the messages being sent by inhibiting some Purkije cells
What type of neuron arises from the inferior olivary nucleus and ascends to the molecular layer to synapse with Purkinje cells or to synapse with deep cerebellar nuclei?
Climbing fibres
What type of messages do climbing fibres carry - weak or strong?
Strong
How many cells do climbing fibres synapse with?
Synapse with ONE purkinje cell
Which two places do climbing fibres travel to?
(1). To the molecular layer of the cerebellar cortex - synapse with Purkinje celsl
(2). To deep cerebellar nuclei
What is the difference between mossy fibres and climbing fibres?
Mossy fibres = weak messages - therefore synapse with lots of different purkinje cells.
Climbing fibres = strong messages - therefore synapse with only one purkinje cell
What type of output do purkinje cells have? Excitatory or inhibitory?
Inhibitory
In which layer of the cerebellum cortex do mossy fibres branch?
The granular layer
What can mossy fibres innervate?
The granular layer of the cerebellar cortex
OR
Deep cerebellar nuclei
What type of cells do mossy cells synapse with?
Granule cells
Do mossy fibre cells innervate one or lots of granule cells?
Lots - weaker signal
What do granule cells synapse with? How?
(1) Purkinje cells
Through parallel fibres
(2). Golgi cells
Through parallel fibres
What are Golgi cells in the cerebellum important for?
Negative feedback of the granule cells
How can Golgi cells in the cerebellum be stimulated?
(1). Via parallel fibres of granule cells (negative feedback mechanism)
(2). Via mossy fibres - again inhibit granule cells (feed forward inhibition)
Which cell is responsible for turning off (inhibiting) granule cells and therefore purkinje cells?
Golgi cells
Which cells of the cerebellum are thought to be involved in synaptic plasticity creating a learned response / motor learning?
Purkinje cells
How does motor learning occur in the cerebellum cellularly?
Repetition of motor action = synaptic plasticity of Purkinje cell response to the mossy fibre and climbing fibre stimulation.
This leads to a change in pattern of coded signals to the cerebral cortex = learning of new motor skill.
What can pathology of the cerebellum cause?
Disfunction of movement and tone
Which is more likely to cause symtoms - pathology of cerebellar nuclei or pathology of cerebellar cortex? Why?
Pathology of cerebellar nuclei - because lots of different pathways run though the nuclei.
Pathology of the cerebellar cortex is also less likely to cause visible symptoms due to fractionated somatotopy.
What does pathology of the cerebellar hemispheres (paravermal) affect?
Ipsilateral function - so problems will appear on the same side of the body as the pathology in the cerebellum.
What does pathology of the cerebellar vernix affect?
Trunk (axial muscles) and eye movements
What are the symptoms of a cerebellar problem?
Incoordination
Tremor
Unsteadiness
Oscillopsia
Slurring of speech
What is unstable vision called?
Oscillopsia
What are the clinical signs of a cerebellar problem?
Finger nose incoordination (past-pointing, dysmetria)
Dysdiadokokinesia
Heel shin incoordination
Wide based gait
Hypotonia
Nystagmus
Staccato speech
What is the term for a patient who cannot move flip one hand backwards and forwards on another hand called?
Dysdiadokokinesia
What symptoms and signs would you expect for a lesion which affects one hemisphere of the cerebellum?
Ipsilateral past pointing
Dysdiadokokinesia
Intention tremor
Why do you get intention tremor with a lesion to lateral cerebellar hemisphere?
Lateral hemisphere –> dentate nucleus –> thalamus –> cerebral cortex. Feedback to motor cortex is disrupted = intentional tremor
What causes of cerebellar dysfunction can you name?
Tumor
Abscess
Vascular lesion (stroke)
Alcoholic cerebellar degeneration
Which part of the cerebellum is usually affected by alcoholic cerebellar degeneration?
Midline anterior vermis and paravermis
What are the signs and symptoms of alcoholic cerebellar degeneration? Why?
Incoordination in legs > arms
Truncal ataxia most marked
Axial muscles are found more medially (vermis) and legs are represented in anterior paravermis
Why does alcoholic cerebellar degeneration occur?
Nutritional deficiencies = degeneration of Purkinje cells - which is more marked in the anterior vermis & paravermis.
What are the axial muscles?
Muscles of the midline - inc tail, trunk and eyeballs
P has a medulloblastoma affecting the fastigial nucleus and vermis - what symptoms and signs would you expect?
Truncal ataxia - due to midline vermis compression
Nystagmus - connections via fastigial and vestibular nuclei are affected
