Cerebellum and pathways

Objectives - cerebellum

Identify the anatomical divisions of the cerebellum

Identify the functional divisions of the cerebellum

Explain what observable functions each division of the cerebellum is involved with

Describe each afferent and efferent pathway – structure, function, neurotransmitters, and neuron type if applicable

Describe or draw the layers of the cerebellar cortex

Describe or draw the types of neurons in the cerebellar cortex

Identify which neurons are excitatory (glutamate & aspartate) and which are inhibitory (GABA)

Explain how the neurons in the cerebellar cortex interact

Plan of attack

Lecture 9 – cerebellar structure and organization, afferent cerebellar pathways, efferent cerebellar pathways

Lecture 10 –cerebellar histology, motor learning

Overall function

Ataxia with intention (action) tremor:

https://www.youtube.com/watch?v=5eBwn22Bnio

Ataxia with gross limb movement dysfunction:

https://www.youtube.com/watch?v=qKGicpQLt6M

Ataxic Gait:

https://www.youtube.com/watch?v=FpiEprzObIU

Dysmetria:

https://www.youtube.com/watch?v=jnQcKAYNuyk

Dysdiadochokinesia:

https://www.youtube.com/watch?v=gNZFSUdL_uc

Anatomical structure

Gray Cortex! (Folia = sulci and gyri)

Floculonodular lobe

Anterior lobe

Posterior lobe

White Matter

Cerebellar peduncles -> Arbor Vitae (tree of life!)

Deep Nuclei

4 total (per hemisphere)

View of entire cortex

Functional structure

Vestibulocerebellum (floculonodular lobe)

Balance during stance/gait, coordinates eye and body movements

Associated with vestibular nuclei

Spinocerebellum (vermis and paravermis)

Coordination of limb movements

Associated with spinal cord directly and indirectly

Cerebrocerebellum (lateral hemispheres)

Planning and preparation for movement, fine motor control

Associated closely with motor cortex (pre-central gyrus)

Cerebellar nuclei

Lateral – Dentate

Middle – Interposed;

Emboliform and Globose

Medial – Fastigial

Nuclei connections

Fastigial – vestibulocerebellum to vestibular nuclei and eye motor centers

Interposed – spinocerebellum to contralateral red nucleus

Rubrospinal tract

Dentate – cerebrocerebellum to thalamus

Planning and control of voluntary movements

All cerebellar efferents synapse in the deep nuclei

The nodulus connects to which nucleus?

A. FastigialB. GloboseC. EmboliformD. Dentate

Fasti

gial

Globose

Embolifo

rm

Dentate

94%

6%0%0%

Your patient has difficulty with fine motor control. Which nucleus would be associated?

A. FastigialB. GloboseC. EmboliformD. Dentate

Fasti

gial

Globose

Embolifo

rm

Dentate

3%

97%

0%0%

Which part of the cerebellum would be associated with the same patient?

A. VestibulocerebellumB. SpinocerebellumC. Cerebrocerebellum

Vestibuloce

rebellu

m

Spinoce

rebell

um

Cerebro

cere

bellum

0%

100%

0%

Cerebellar Afferents

4 Spinocerebellar Tracts

Pontocerebellar

Reticulocerebellar

Raphecerebellar

Hypothalamocerebellar

Ceruleocerebellar

Olivocerebellar

Spinocerebellar Tracts (cross-section)

Cuneocerebellar Pathway

Information ascends in the cuneate tract

Synapses in the Accessory cuneate nucleus (lateral to the cuneate nucleus in the medulla)

Second neuron ascends ipsilaterally through ICP to cerebellar nuclei and cortex

Entire pathway is IPSILATERAL

Carries sensory information from UE

Posterior Spinocerebellar Pathway

Ascends ipsilaterally in PSC tract

Synapses in spinal cord

Passes through ICP

Ends in cerebellar cortex and nuclei

Carries sensory information from LE

Rostral Spinocerebellar Pathway

Ascends ipsilaterally

Runs with cuneocerebellar, and then splits and runs with ASC after it crosses

Enters cerebellum through SCP (like ASC)

Carries sensory information from UE

Anterior Spinocerebellar Pathway

Ascends contralaterally in ASC tract

Crosses through the SCP

Ends in ipsilateral cerebellar cortex and nuclei

Carries sensory information from LE

Which pathway carries sensory information to the cerebellum from the UE and goes through the SCP?

A. ASCB. CuneocerebellarC. PSCD. Rostrocerebellar

ASC

Cuneocereb

ellar

PSC

Rostroce

rebell

ar

0%

100%

0%0%

The ICP is damaged. Which of the following is TRUE?

A. Ipsilateral sensory info to the cerebellum from the UE is completely gone.

B. Contralateral sensory info to the cerebellum from the LE is completely gone.

C. Ipsilateral sensory info from both limbs is reduced.

D. Contralateral sensory info from both limbs is reduced.

Ipsilate

ral se

nsory

info to th

e c...

Contralat

eral se

nsory

info

to th

e...

Ipsilate

ral se

nsory

info from bot..

.

Contralat

eral se

nsory

info

from ...

19%

0%

81%

0%

Spinocerebellars

Which is the red?

Which is the blue?

Which is the green?

Which is missing and where would it be?

All MOSSY FIBERS

Other cerebellar afferents

Pontocerebellar

Reticulocerebellar

Raphecerebellar

Hypothalamocerebellar

Ceruleocerebellar

All MOSSY FIBERS

Olivocerebellar Pathway

Information from Inferior Olivary Nucleus

Crosses to the ICP

Ends in the cerebellar cortex and nuclei

CLIMBING FIBERS

Which of the following do NOT connect to the #reticular formation?

A. CeruleocerebellarB. PontocerebellarC. RaphecerebellarD. Reticulocerebellar E. Hypothalamocerebellar

Ceruleo

cere

bellar

Pontoce

rebella

r

Raphecere

bellar

Reticuloce

rebell

ar

Hypothala

moce

rebella

r

5%

44%49%

2%0%

Cerebellar afferent Drawing!

Split the 4 spinocerebellars into 2 groups – draw 2 pathways per image

Either by LE vs. UE, or by similar pathways (Cuneo and Post., Rostral and Ant.)

Draw olivocerebellar tracts

Add essential information to each drawing along the side:

Where does the pathway decussate (if it does)?

Which cerebellar peduncle does it go through?

What information does it carry?

What type of fibers is it? (mossy or climbing)

Cerebellar efferents

Corticonuclear

Nucleocortical

Corticovestibular

Other efferents

Cerebellar Corticonuclear Pathway “Fibers”Cerebellar cortex (Purkinje cells) → cerebellar nuclei

Cerebellar Nucleocortical Pathway “Fibers”Cerebellar nuclei neurons (Nuclei Cells) → cerebellar cortex

VC = Vermal Cortex

IC = Intermediate CortexLC =

Lateral Cortex

Dentate

Embo

lifo

rm Glo

bose

Fast

igi a

l

White Matter = Arbor Vitae

Cerebellar Corticovestibular Pathway

o Starts in: Purkinje cells within vermis,

nodulus, & focculonodular lobe (Cerebellar Cortex)

o Through Inferior Cerebellar Peduncle

o Ends in: Vestibular nuclei within the

brainstem

Inf. Peduncle

All of the neurons with somas in the deep cerebellar nuclei exit the cerebellum.

A.TrueB.False

True

False

91%

9%

The corticovestibular tract is from the cerebellar cortex directly to the vestibular nuclei.

A.TrueB.False

True

False

97%

3%

Conclusion

Read for Wednesday

L-E ch. 11 pt. 1

We will discuss cerebellar histology Wed. and talk about how the plasticity plays a role a motor learning!

Nuclear Efferents

Dentate and Interposed nuclei

Neurons cross in SCP

Go to Thalamus, Pontine nuclei, Reticular formation, Red nucleus, Olivary bodies, Oculomotor complex (nystagmus)

From thalamus up to cerebral cortex

From other structures, straight down the spinal cord

1. Cerebellorubral route connects the rubrospinal route

• cerebellum → red nucleus → SC

2. Cerebelloreticular route connects the reticulospinal route

• cerebellum → reticular formation → SC

3. Cerebellothalamic route connects the thalamocortical route

Which then connects to the corticospinal route

• cerebellum → thalamus → cortex → SC

*Cerebellar nuclei influence motor control

Cerebellar Efferent Fibers & Motor Control

Takeaways – cerebellar efferents

All efferents from cerebellar nuclei (Dentate, Interposed, Fastigial)

Fastigial goes to vestibular nuclei

Bilateral

Dentate and interposed go to thalamus, red nucleus, pontine nuclei, olivary nuclei, and #RF

All decussate in SCP

All decussate again to go down spinal cord

All information ends up being IPSILATERAL

Which of the following are bilateral tracts?

A. HypothalamocerebellarB. OlivocerebellarC. RostrospinocerebellarD. Corticovestibular

Hypothala

moce

rebella

r

Olivoce

rebella

r

Rostrosp

inocere

bellar

Cortico

vesti

bular

0% 0%0%0%

Objectives - cerebellum

Identify the anatomical divisions of the cerebellum

Identify the functional divisions of the cerebellum

Explain what observable functions each division of the cerebellum is involved with

Describe each afferent and efferent pathway – structure, function, neurotransmitters, and neuron type if applicable

Describe or draw the layers of the cerebellar cortex

Describe or draw the types of neurons in the cerebellar cortex

Identify which neurons are excitatory (glutamate & aspartate) and which are inhibitory (GABA)

Explain how the neurons in the cerebellar cortex interact

Histology!

Cerebellar cortex histology, once understood, gives a really awesome and essential understanding to motor learning!

3 layers of cerebellar cortex

Molecular (outer) layer

Purkinje layer

Granular (inner) layer

Zoomed in!

Reference: White area is air – outside the folia

(a sulcus)

Notice:

molecular layer,

purkinje cells,

granular layer

Molecular layer

Parallel fibers (axons of granular cells, telephone wires)

Climbing Fibers (like vines on the purkinje tree)

Dendrites of purkinje cells (tree like)

Basket and Stellate cells

Purkinje layer

Purkinje somata

Granular layer

Granule somata

Golgi cells

Zoomed in!

Reference: White area is air – outside the folia

(a sulcus)

Notice:

molecular layer,

purkinje cells,

granular layer

Afferent fibers

Information coming IN!!

Climbing Fibers (vines)

Mossy Fibers (stimulate granule cells)

Mossy fibers (afferent pathways)

Come from all afferent pathways except olivocerebellar

List them!

Excite granular cells (parallel fibers, telephone wires) with high frequency, weak EPSP

glutamate

Bring in information constantly on what’s planned and what’s actually happening with somatic motor control

Like the internet, all information is transmitted through telephone cable system

Climbing fibers (olivocerebellar)

Powerful excitation to purkinje cells (vines on purkinje tree)

glutamate

Respond to interruptions in balance (from reflexes in spinal cord)

Olivocerebellar

Only fire when an immediate reaction is required!

Like the CIA when something important is found on the internet!

Granule cells

Granule cells (parallel fibers in molecular layer)

Telephone wires

All run parallel, highly structured in cortex

Granule cells

Soma is in granular layer

Axon ascends to molecular layer, splits, and runs as parallel fiber

Excitatory but weak to purkinje cells – requires multiple action potentials to break threshold

glutamate

Purkinje neurons

Named after one of the first neuroscientists

Main efferent neurons (cortex to deep cerebellar nuclei)

Have a huge dendritic tree in the molecular layer

Are acted on by:

Parallel fibers

Climbing fibers

Efferent fibers

Purkinje neurons (inhibitory)

GABA

Giant dendritic tree

Weak but frequent stimulation from granule cells

Which pathways?

Strong but infrequent stimulation from climbing fibers

Which pathways?

Inhibit deep nuclei (DEGF)

Inhibitory interneurons

Basket cells

Inhibit purkinje cells

Golgi cells

Inhibit granule cells

All GABA

Basket cells

Axon terminals wrap around purkinje cell bodies like baskets

Inhibit purkinje cells

GABA

Excited by parallel fibers

Golgi cells

Inhibit granule cells

GABA

Located in granular layer

Excited by parallel fibers

Task

In your team, create a short video (with phones or other devices) explaining how information enters the cerebellum, how the neurons interact, and how the information is sent out of the cerebellum.

Include: Mossy fibers and pathways that fall into this category

Climbing fibers and pathway(s) that fall into this category

Granule cells with parallel fibers

Purkinje cells

Corticonuclear and nucleocortical tracts

Excitation vs inhibition (and neurotransmitters)

Today in class: create a plan, write up a script

Post a link to your video on the wiki by Friday Sunday midnight. (part of participation grade – out of 10 points)

Wiki page: Cerebellar Histology Videos (available through term lists and images)

Reciprocal Inhibition

Interneurons inhibit purkinje and granule cells

Only excitation comes from mossy and climbing fibers

Result is inhibitory outputs

Motor learning and the cerebellum

Theory:

When climbing fiber input and parallel fiber input occur at the same time on the purkinje cell, the post-synaptic purkinje dendrite experiences long-term depression (LTD)

Beyond this is yet unknown but studying the cerebellar cortex has surfaced these three hypotheses:

Learning and memory can result from modifications of synaptic transmission.

Synaptic modifications can be triggered by the conversion of neural activity into intracellular second messengers.

Memories can result from alterations in existing synaptic proteins.

Cerebellum Overview

Functional structure

Vestibulocerebellum

Spinocerebellum

Cerebrocerebellum

Pathways

Afferents

Efferents

Cerebellar histology

Neuron types

Organization of the Course

Spinal Cord

Brainstem/ Cerebellum

Sensory Pathways

Cerebrum

Motor Pathways

Exam formats

Midterm:

60 MC

Mix of know, understand, apply questions

Tag Test:

15 stations, 5 questions per station = 75 questions

New format: 3-2-1 done

Lab closes end of day Wednesday March 4

Conclusion

Start discussing the rest of the sensory pathways Monday!

Assignment #2 due Monday

Only 3 lectures left until Midterm Exam!!

Finish creating video, post to wiki by Friday midnight!