1. Cerebellum and pathways

2. 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

3. Plan of attack
Lecture 9 – cerebellar structure and organization, afferent cerebellar pathways, efferent cerebellar pathways
Lecture 10 –cerebellar histology

4. Overall function Ataxia with intention (action) tremor:
Ataxia with gross limb movement dysfunction:
Ataxic Gait:
Dysmetria:
Dysdiadochokinesia:
Ataxia – without coordination
Discuss intention vs. resting tremor
Dys – bad, difficult, disordered
Diadochokineasia – alternating sequential movements
Metria – range of movement

5. 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)
Archi – oldest
Paleo – next oldest
Neo – newest

6. View of entire cortex
Unfolded cerebellum

7. 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)

8. Cerebellar nuclei Lateral – Dentate Middle – Interposed;
Emboliform and Globose
Medial – Fastigial

9. 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

10. Inferior view
What does the vermis do? Spinocerebellum – gross limb movements
How do I know this is inferior? Tonsils are visible

11. Anterior view
What do the nodulus and flocculus do? Vestibulocerebellum – balance in gait and stance, integration of eye movements
What does the tonsil do? (posterior lobe, paravermis) spinocerebellum – gross limb movements
What do the large hemispheres do? Cerebrocerebellum – smooth out voluntary movements, fine motor control

12. Cerebellar Afferents 4 Spinocerebellar Tracts Pontocerebellar
Reticulocerebellar
Raphecerebellar
Hypothalamocerebellar
Ceruleocerebellar
Olivocerebellar

13. Spinocerebellar Tracts (cross-section)

14. 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

15. 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

16. Rostral Spinocerebellar Pathway
Ascends ipsilaterally
Joins ASC (?)
Enters cerebellum through SCP (like ASC)
Carries sensory information from UE

17. Anterior Spinocerebellar Pathway
Ascends contralaterally in ASC tract
Crosses through the SCP
Ends in ipsilateral cerebellar cortex and nuclei
Carries sensory information from LE

18. Spinocerebellars Which is the red? Which is the blue?
Which is the green?
Which is missing and where would it be?
All MOSSY FIBERS

19. Other cerebellar afferents
Pontocerebellar
Reticulocerebellar
Raphecerebellar
Hypothalamocerebellar
Ceruleocerebellar
All MOSSY FIBERS
Know functions!

20. Olivocerebellar Pathway
Information from Inferior Olivary Nucleus
Crosses to the ICP
Ends in the cerebellar cortex and nuclei
CLIMBING FIBERS

21. 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)

22. Cerebellar efferents Corticonuclear Nucleocortical Corticovestibular
Other efferents

23. Cerebellar Corticonuclear Pathway “Fibers”
VC = Vermal Cortex
IC = Intermediate Cortex
LC = Lateral Cortex
Cerebellar Corticonuclear Pathway “Fibers”
Cerebellar cortex (Purkinje cells) → cerebellar nuclei
Cerebellar Nucleocortical Pathway “Fibers”
Cerebellar nuclei neurons (Nuclei Cells) → cerebellar cortex
White Matter = Arbor Vitae
Where can you find Purkinje cells?
Connections Between Parts of Cortex & Nuclei
1. Vermal Cortex → communicates with → Fastigial Nucleus
2. Intermediate Cortex → communicates with → Globose Nucleus & Emboliform Nucleus
3. Lateral Cortex→ communicates with → Dentate Nucleus (Lateral)
* Functions: Both of these pathways function as an internal communication network within the cerebellum
Dentate
Globose
Fastigial
Emboliform

24. Cerebellar Corticovestibular Pathway
Starts in:
Purkinje cells within vermis, nodulus, & focculonodular lobe (Cerebellar Cortex)
Through Inferior Cerebellar Peduncle
Ends in:
Vestibular nuclei within the brainstem
Inf. Peduncle
What does the vestibulocochlear cranial nerve do??? CN #8? Balance, Proprioception , Hearing, & Equilibrium
Cerebellar Corticovestibular fibers allow communication between the cerebellar cortex & the brainstem
Function of Cerebellar Corticovestibular Pathway = Combining the motor component of the cerebellum with the balance component of the vestibular nuclei allows for smooth & coordinated movements

25. Nuclear Efferents Dentate and Interposed nuclei Neurons cross in SCP
Go to Thalamus, Pontine nuclei, Reticular formation, Red nucleus, Olivary bodies
From thalamus up to cerebral cortex
From other structures, straight down the spinal cord

26. Cerebellar Efferent Fibers & Motor Control
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
Efferent Fibers make up Routes within the cerebellum that connect to the tracts/routes within the spinal cord Examples of Tracts listed in the book…
Functions:
rubrospinal = muscle tone
reticulospinal = monitors levels of awareness/excitement; modulates sensory, autonomic, and motor activity
corticospinal = somatomotor
Which relate back to the main functions of the cerebellum
The cerebellum influences other pathways
Look at the RED Pathway:
Red Nucleus - crosses thru decussation - stays on that side all the way down to SC

27. 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

28. 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!

29. 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

30. 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

31. Reference: White area is air – outside the folia (a sulcus) Notice:
Zoomed in!
Reference: White area is air – outside the folia
(a sulcus)
Notice:
molecular layer,
purkinje cells,
granular layer

32. 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

33. Purkinje layer
Purkinje somata

34. Granular layer
Granule somata
Golgi cells

35. Reference: White area is air – outside the folia (a sulcus) Notice:
Zoomed in!
Reference: White area is air – outside the folia
(a sulcus)
Notice:
molecular layer,
purkinje cells,
granular layer

36. Afferent fibers Information coming IN!! Climbing Fibers (vines)
Mossy Fibers (stimulate granule cells)

37. 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
Constant barrage of information from everywhere about everything

38. 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!
When something is thrown off and there is immediate danger, these neurons are a direct route to the purkinje cells and cause an immediate firing.
Climbing fibers – when rock climbing, fast reactions could save your life!

39. Granule cells Granule cells (parallel fibers in molecular layer)
Telephone wires
All run parallel, highly structured in cortex

40. 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

41. 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
Inhibitory - GABA

42. Efferent fibers Purkinje neurons (inhibitory) Giant dendritic tree
GABA
Giant dendritic tree
Weak but frequent stimulation from granule cells
Which pathways?
Strong but infrequent stimulation from climbing fibers
Inhibit deep nuclei (DEGF)

43. Inhibitory interneurons
Basket cells
Inhibit purkinje cells
Golgi cells
Inhibit granule cells
All GABA

44. Basket cells
Axon terminals wrap around purkinje cell bodies like baskets
Inhibit purkinje cells
GABA
Excited by parallel fibers
Inhibit an inhibitory neuron…. Action potential allowed to propogate

45. Golgi cells Inhibit granule cells Located in granular layer
GABA
Located in granular layer
Excited by parallel fibers
Inhibit a neuron that excites an inhibitory neuron… action potential is allowed to propogate

46. 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 midnight. (part of participation grade – out of 10 points)

47. Figure 1. This drawing represents the cytoarchitecture of the cerebellum. Its cellular components are:
1. Basket cells. 2. Climbing fibers. 3. Purkinje neurons. 4. Golgi cells. 5. Mossy fibers. 6. Stellate cells. 7. Parallel fibers. 8. Granule cells. 9. Lugaro cells. 10. Brush cells. Also, it shows the three different layers of cerebellar cortex: molecular layer (ML), Purkinje layer (PL) and granule layer (GL), as well as the white matter (WM). Arrows points out the ascending directions of the climbing (left) and mossy fibers (right) coming from the inferior olive and the brain, respectively.

48. Reciprocal Inhibition
Interneurons inhibit purkinje and granule cells
Only excitation comes from mossy and climbing fibers
Result is inhibitory outputs

49. 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.
For more information, see pages of Bear.

50. Cerebellum Overview Functional structure Pathways Cerebellar histology
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
Pathways
Afferents
Efferents
Cerebellar histology
Neuron types

51. Organization of the Course
Spinal Cord
Brainstem/ Cerebellum
Sensory Pathways
Cerebrum
Motor Pathways
Cranial Nerves
Other Pieces of the puzzle
Overview and Development

52. 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!