Kin 411: Cerebellum (All 17, 18, 19)

Which side of the hemisphere is non dominant? Main fx?

Usually the right hemisphere is non dominant

Main fx:

1. Visual spatial analysis

2. Spatial attention

What is the role of the non dominant hemisphere.
What area of the brain exactly plays that role? What inputs does it use to carry out that role?

The parietal area of non dominant (right) hemisphere plays a role as a control center to attend to critical information in the env and filter out non-relevant info in the entire spatial field.

It uses: visual, sensory and motor inputs

What is neglect?

Damage to right parietal association cortex or frontal cortex causes inability to attend to/focus on/identify sensory information coming from the contralateral side.

Neglect often happens on one side of the body.

What is hemi-spatial neglect? What causes it?

Ignoring or failing to attend to activity on one side of the spatial field (visual, sensory, motor)
It is caused by a stroke in the non-dominant (right) parietal cortex

Damage to right (non-dom) hemisphere parietal association cortex, extending to frontal cortex, causes what and where

Causes hemi-spatial neglect (inability to attend to important sensory info or movements) on the contralateral side

What is common about strokes that cause hemineglect?

Strokes can be of different sizes but they’re all located at the parietal/frontal association cortex leading to hemineglect

How is the attention field divided in a normal brain

Right parietal cortex/hemi:

• Attends to entire space but more attention on contralateral (left) space

Left parietal cortex/hemi:

• Limited attention

• All attention focus on right spatial field

Together they cover the entire attention field on a normal brain

Non dom ____ cortex damage, also called ___ hemi lesion, causes severe ___ neglect

parietal; right hemi lesion; left neglect

Describe what happens during a right hemisphere lesion

• Complete neglect of the left spatial field

  • i.e. Lose ability to attend to info (visual, sensory, motor field)

• Right spatial field still present, albeit less so, as left hemisphere can still somewhat attend to it

Does left hemisphere damage show neglect on any side? Why or why not? Is there a difference between the strength of attention for either field?

No, left hemisphere damage does not show any neglect on right spatial field, or any field for that matter.

This is because right hemisphere has a specialization for attention and can attend to the whole field

• Attention is stronger for the left spatial view but still able to attend to the right field

Hemi-neglect always appears in which visual space? Which visual side of the body?

Hemi-neglect appears in the left visual space, on the left side of the body

Damage to both hemisphere leads to ?

Lead to neglect of the entire visual field altogether

Damage to left (dominant) hemisphere leads to?

No neglect, as right hemisphere is intact and it has specialization to attend to the whole field.

What are the types of neglects?

1. Sensory neglect: Visual, tactile, or auditory neglect

2. Motor-intentional neglect

3. Combination of sensory and motor neglect

4. Conceptual Neglect

What’s key to remember about sensory neglect?

It is NOT an inability to receive raw sensory input. PCML, somatosensory cortex is still intact. They’re able to focus on a specific area individually when tested

It is the inability to attend to sensory input when they need to “span their attention” ie when testing both sides together

What is Motor-intentional neglect - what can pt do, what can’t they do, and what causes it?

• Pt able to do unilateral movements when focusing individually

• Inability to do motor movements bilaterally

  • i.e when asked to move both sides, will neglect movement on left side, only do movement on the right side

  • due to damage on right (non dom) hemisphere leading to left hemineglect

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Conceptual Neglect

Damage to right (non dom) parietal cortex leading to:

1. Representational neglect

2. Anosognosia

3. Hemiasomatognosia

Representational neglect: is a form of? caused by? leads to?

Form of conceptual neglect due to damage to right parietal cortex

Leads to: attending to right side conceptual memories only e.g. remembering the right side buildings on the map

Anosognosia

No awareness of hemi-neglect or -plegia

Neglect or lack of awareness of the actual neglect itself OR that they have a particular injury

e.g. stroke causes hemi-neglect to the left side of the body but pt not aware that they have Sx/deficits on the left side of the body

Hemiasomatognosia

Disowning limbs: disowning left side limbs (extreme conceptual neglect)

Dressing Apraxia

Apraxia is usually due to loss of skilled movement due to damage to the left hemisphere

BUT, dressing apraxia is due to RIGHT parietal lesion

• Pt forgets to attend to the left side of their body while dressing

• This is a symptom of neglect, NOT a symptom of loss of skilled movement

Alien Hand

Damage to Supplementary Motor Area or corpus callosum on the right (non dominant) hemisphere

Left hand is “out of control” i.e. acts autonomously, mischievously

Theory behind Alien Hand

Two consciousness on each side of the brain:

• Dominant consciousness keeps non-dominant consciousness in check

• When we hurt the corpus callosum, the right hemisphere can do whatever it wants since it’s not being checked by left (dom) hemisphere

Cerebellum location with respect to skull

• Sits nestled in the posterior fossa in the base of skull

• Covered by the tentorium cerebelli, which separates it from the inferior occipital lobe

General cerebellum location

• Posterior to the brainstem

• It makes up the dorsal wall of the CSF filled 4th ventricle

• It is nestled in the posterior fossa where it is separated from the occipital and temporal lobe by the tentorium cerebelli

Cerebellum acts like a mini brain. ____ matter on the ___ surface making the folds. The ___ folds are called _____.
_____ matter projects ____ as tracts

Grey matter on the outer surface
The outward folds are called folia

White matter project inwards as tracts

Label A-F

A- Fourth Ventricle

B- Anterior Lobe

C- Tentorium cerebelli

D- Primary fissure

E- Posterior Lobe

F- Posterior fossa

Label A-F

A- Vermis

B- Anterior lobe

C- Primary fissure

D- Posterior lobe

E- Intermediate zone

F- Lateral zone

Label A-H

A- Superior cereb ped

B- Middle cereb ped

C- Inferior cereb ped

D- Postero-lateral fissure

E- Nodulus

F- Flocculus (floculli on both sides)

G- Flocculonodular lobe

H- Primary fissure

Cerebellum anatomy

Cerebellum has 3 major lobes separated by 2 key landmarks (fissures):

1. Anterior lobe

   • Primary fissure separates anterior and posterior lobe

2. Posterior lobe

   • Postero-lateral fissure separates inferior posterior lobe from the flocculo-nodular lobe

3. Flocculo-nodular lobe

Primary fissure

Separates anterior and posterior lobe

Postero-lateral fissure fx. Which view is it visible from?

• Only visible from anterior view

• Separates inferior posterior lobe from the flocculo-nodular lobe

What is flocculo-nodular lobe made up of?

Nodulus in the center and 2 flocculi (bulges) on either side

How do you make a cerebellum?

Stretch it to look like an octupus

Anterior lobe top 1/3

Divided by primary fissure

Middle 1/3 is posterior lobe

Bottom tentacles has the nodulus in the middle with 2 flocculi on each side

What are folia?

They are outward folds of grey matter on the cerebellum.

They fold to connect to the white matter tracts that go inward

What are the 4 functional region of the cerebellum? Explain where they are located

Think of the posterior view of cerebellum like a moth

1. Vermis: central region (body of the moth)

2. Intermediate zone: middle 1/3 region

3. Lateral zone: lateral 2/3 region

4. Flocculo-nodular zone:

   1. made up of flocculo-nodular zone

   2. only seen from anterior view

Where are the 4 functional region of the cerebellum projecting to

To the deep cerebellar nuclei

How are the functional regions of the cerebellum associated with its nuclei?

Functional grey matter region of the cerebellum are aligned with their corresponding deep nuclei

Name the deep nuclei of the cerebellum and their associated fx region

1. Dentate nuclei = lateral zone

2. Interposed nuclei = Intermediate zone (memory trick: Both are I)

3. Fastigial Nucleus = vermis + flocculo-nodular zone

Dentate nuclei

• Aligns with the lateral zone

Interposed nuclei

• Made up of 2 smaller nuclei:

  1. Embolus nucleus

  2. Globus nucleus

• Aligns intermediate zone

Fastigial nucleus

• Along the midline

• Aligns with the vermis and flocculonodular zone

How to remember Order of Nuclei in the cerebellum

From most lateral → most medial

Dont = Dentate

Eat = Emobolus

Greasy = Globus

Foods = Fastigial

*Emobolus + Globus = interposed nuclei

Where do these deep nuclei in cerebellum receive information from?

Deep nuclei in cerebellum receive info from the axons of the grey matter

Purkinje cells in the:

Lateral zone → dentate nuclei

Intermediate zone → interposed nuclei

Vermis + flocculonodular zone → fastigial nucleus

All information are carried to and from cerebellum via _____

Cerebellar peduncles

What are the cerebellar peduncles? Names? Fx? What level of the brain are they?

They are projections of white matter in and out of the cerebellum

Superior, middle, inferior peduncles

They carry info to and from cerebellum

They come out at the level of the pons giving it its bulge shape

What are the 3 cerebellar peduncles

1. Superior cerebellar peduncle

2. Middle cerebellar peduncle

3. Inferior cerebellar peduncle

Label A-C

A- Superior cereb peduncle

B- Middle cerebellar peduncle

C- Inferior cerebellar peduncle

Cerebellar peduncles are not to be confused with ?

Cerebral peduncles which are tracts of white matter running down the anterior surface of the midbrain

What are Purkinje cells

Neurons specific to the cerebellum, found in the exterior surface of the cerebellum and they project into the deeper nuclei

Fx of superior cerebellar peduncles

Superior cerebellar peduncles carry information from cerebellum and project OUT into the nervous system

Fx of middle and inferior cerebellar peduncles

Middle and inferior cerebellar peds is to carry inputs INTO the cerebellum

Describe path of info into and out of cerebellum

1. Info comes into cerebellum via inferior and middle cerebellar peduncles

2. Gets process in the cerebellum by grey matter and purkinje cells

3. Axons from purkinje cells project into the deep nuclei according how they are aligned (dont eat greasy food)

4. Deep nuclei does further processing of the info

5. Info is projected back out into the nervous system by the superior cerebellar peduncle

What are the 3 main input pathway to the cerebellum? What do they do?

1. Pontocerebellar fibers

2. Spinocerebellar pathways

   • Dorsal spinocerebellar tract

   • Cuneocerebellar tract

3. Vestibular inputs

Inputs from these 3 control ongoing movement + coordinate movement

Input pathway: Coming from → Cells Projecting to Cerebellum → Entering thru which Cerebellar peduncle

Pontocerebellar fibers

Pontocerebellar fiber: Motor info coming from cortex → pontine nuclei → middle cereb peds

Input pathway: Coming from → Cells Projecting to Cerebellum → Entering thru which Cerebellar peduncle

Dorsal spinocerebellar tract

Spinocerebellar Pathways: Proprioceptor legs → Nucleus Dorsalis of Clark (C8 - L2) [ipsi] → Enter Inferior cerebellar penduncle (ipsi)

Input pathway: Coming from → Cells Projecting to Cerebellum → Entering thru which Cerebellar peduncle

Cuneocerebellar Tract

Cuneocerebellar Tract: Proprioceptor/vibration/LT from arms → External cuneate nucleus (caudal medulla) [ipsi} → Inferior cerebellar penduncle (ipsi)

Input pathway: Coming from → Cells Projecting to Cerebellum → Entering thru which Cerebellar peduncle

Vestibular inputs

Vestibular inputs: Vestibular system → vestibular ganglia + vestibular nuclei (ipsi) → juxtarestiform body (subsection of inferior peduncle) ipsi

Where do inputs into cerebellum come via

Middle and inferior cerebellar peduncles

Inputs to the cerebellum: motor

One input coming into cerebellum is ongoing motor information from the motor cortex

• Copy of motor info is sent from cortex to cerebellum via pontocerebellar pathway

• Cortical pontine fibers (axons from the motor cortex) descend ipsilaterally synapsing onto pontine nuclei

• Ponto-cerebellar fibers from pontine nuclei cross the midline @ pons

• Enter cerebellum via middle cerebellar peduncle

How does signal of a motor plan to move the right hand travel from cortex to cerebellum

Signal to move right hand originates at the right cortex

Copy of that input from right motor cortex travel ipsilaterally to the right pontine nuclei

Axons from pontine nuclei decussate @ pons

Enter left cerebellum thru the middle cerebellar peduncle

Inputs to the cerebellum: Sensory

Afferent copy (external feedback) from periphery is carried into cerebellum, through the inferior cerebellar peduncle, via two Spinocerebellar Pathways:

1. Cuneo-cerebellar tract

2. Dorsal spinal-cerebellar tract

Both tracts resemble the PCML pathway

Cuneo-cerebellar tract

Sensory info coming from upper arm and trunk enter lateral part of the posterior column @ fasiculus cuneatus

Travels up to the caudal medulla and synapse onto Nucleus Cuneatus

Collaterals from Nucleus Cuneatus synapse onto External Cuneate Nucleus @ caudal medulla

Travel up ipsilaterally to enter the cerebellum via the Inferior Cerebellar Peduncle

Dorsal Spinal-cerebellar tract

Sensory info coming from lower leg enter the medial part of posterior column @ fasiculus gracilis

Collaterals from Fasiculus Gracilis synapse onto the Nucleus Dorsalis of Clark @ intermediate zone of grey matter of the SC, at the same level

• NDC collaterals are found at every level from C8 → L2/L3

Axons from NDC travel to the lateral column of the SC, at the same level

Start traveling ipsilaterally up the Spinocerebellar tract

Enter the cerebellum via the inferior cerebellar peduncle

How is sensory info from lower leg sent to cerebellum?

Sensory info from leg/foot travel via the Spinocerebellar pathway:

Inputs from periphery, such as foot, travels to contralateral somatosensory cortex

A Copy of that goes to the ipsilateral cerebellum

Fasiculus gracilis, which receives the input from legs at the SC, synapses onto the Nucleus Dorsalis of Clark in the intermediate zone of the SC at the same level

NDC send axons to lateral column of SC at the same level

Start traveling ipsilaterally up the SC via the lateral column on the Dorsal Spinocerebellar tract

Enter cerebellum via inferior cerebellar peduncle

How is sensory info from arms/trunk sent to cerebellum?

Sensory info from arms/trunk travel via the Cuneocerebellar tract:

Inputs from periphery, such as arms, travels to contralateral somatosensory cortex

Copy of that goes to the ipsilateral cerebellum

Fasiculus Cuneatus, which receives the input from arms at the SC, travels up to caudal medulla and synapse onto Nucleus Cuneatus

Collaterals from Nucleus Cuneatus synapse onto the External Cuneate Nucleus @ caudal medulla

Axons then travel up ipsilaterally via the Cuneocerebellar Tract

Enter cerebellum via inferior cerebellar peduncle

Nucleus Dorsalis of Clark

Elongated nucleus found in the intermediate zone of grey matter on the SC

Travels from C8 to L2/L3

Collaterals from Fasiculus gracilis synapse on it

Carries copies of sensory info from legs + lower trunk

External Cuneate Nucleus

Sits @ caudal medulla, next to Nucleus Cuneatus

Collaterals from Nucleus Cuneatus synapse on it

Carries copies of sensory info from upper trunk + arms

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Inputs to Cerebellum: Vestibular

Mention peduncle it enters thru*

2 connections carrying vestibular input into the cerebellum:

1. Primary vestibular sensory neurons (hair cells in otoliths)

2. Vestibular nuclei (Second order sensory neurons)

• Both vestibular PSN and 2SN have DIRECT projections into the cerebellum via juxtaresitform body (a subsection of inferior cerebellar peduncle)

What is the cerebellum on one side receiving in total?

1. Copy of motor info from contralateral motor cortex via pontocerebellar fibers

2. Copy of sensory info from ipsilateral side via Spinocerebellar (legs) and Cuneocerebellar (arms) tract
   

^ Receives ongoing sensory info & compares it to the planned motor function from the cortex

3. Receive information from the vestibular system via primary neurons (hair cells) and second order neurons (vestibular nuclei)

Outputs from the cerebellum travel via ? Where are outputs sent?

Information from the cerebellum leaves via the Superior Cerebellar Peduncle

Most output will be sent to the cortex via the thalamus

What is the golden rule of cerebellar outputs?

Cerebellar outputs always control the ipsilateral side of the body

It does this either via:

double crossing → ipsilateral control

no crossing → ipsilateral control

Main cerebellar output pathways

Region of cerebellum → Deep nuclei axons project out via → Cerebellar peduncle → Main Output

Lateral, intermediate, vermis, inferior vermis and flocculonodular lobe

• Lateral region → Dentate → Superior peduncle → Contralateral Thalamus

• Intermediate region → Interposed → Superior peduncle → Contralateral Thalamus

• Vermis → Fastigial N → Uncinate fasciculus (superior peduncle) + Juxtarestiform body (inferior peduncle) → Vestibular N + Reticular formation

• Inferior vermis + flocculonodular lobe → Verstibular nuclei + fastigial nuclei → Juxtarestiform body (inferior peduncle) → MLF (eye movement)

__ fasciculus travels with the _ cerebellar peduncle

Uncinate fasiculus → superior peduncle

__ body travels with the _ cerebellar peduncle

Juxtarestiform body → inferior peduncle

What is the lateral cerebellum responsible for?

Lateral region involves motor planning for the LCST ipsilateral to the cerebellum

Describe the output path from lateral cerebellum

Lateral cerebellum is responsible for motor planning:

Cerebellum receives sensory information from the body ipsilaterally

Lateral GM regions of cerebellum take this information and projects into the dentate nucleus for processing

Dentate fibers travel out of cerebellum via Superior Peduncle

Dentate fibers cross the midline @ midbrain at red nucleus

Travel to the contralateral thalamus

Cell bodies from contralateral thalamus project to motor cortex (PreMC, PMC, SMA)

Motor cortex sends out motor commands via LCST which then decussate and reach the limbs ipsilateral to the cerebellum that sent the info

Cerebellum plans movements for parts of the body ___ to itself. It does so by communicating with the ___ motor cortex

ipsilateral to itself; contralateral motor cortex

What is the intermediate region of the cerebellum responsible for

Intermediate region/Interposed nuclei:

1. Control distal limbs ipsilateral to cerebellum

   1. via contralateral motor cortex

2. Influence arms ipsilateral to cerebellum

   1. via contralateral red nucleus → Rubrospinal tract (RST)

Output from intermediate zone for distal limb control

Cerebellum receives sensory information from the body ipsilaterally

Intermediate zone of cerebellum projects into the interposed nuclei

Interposed N project out via Superior Peduncle

Cross the midline @ midbrain

Reach the contralateral thalamus

Cell bodies from thalamus project to motor cortex (PreMC, SMA, PMC), contralateral to the cerebellum

Control distal limbs ipsilaterally

Output from intermediate zone for arm control

Cerebellum receives sensory information from the body ipsilaterally

Intermediate zone of cerebellum projects into the interposed nuclei

Interposed N project out via Superior Peduncle

Cross the midline @midbrain and reach the contralateral red nucleus

Cell bodies from red nucleus travel down Rubrospinal Tract

Control arms ipsilaterally

Describe the outputs via the vermis region of the cerebellum

1. Fastigial Nucleus to Contralateral thalamus to:

   1. Influences Axial muscles (trunk/neck motor areas) bilaterally via ACST

2. Fastigial Nucleus to Vestibular nuclei + Reticular formation bilaterally

   1. Influence balance reflex and general tone

3. Inferior vermis + flocculonodular lobe DIRECTLY to Vestibular nuclei ipsilaterally (no deep nuclei)

   1. Influence Balance + eye movement (VOR)

How do Inf vermis + flocculonodule lobe project out of the cerebellum? What does this allow?

There is a bidirectional connection between vestibular system and cerebellum

This is via Inf vermis + flocculonodular lobe connecting with vestibular system on the same side

This allows for cerebellar control over all vestibular reflexes (VOR, VCR)

What is the uncinante fasciculus?

Fibers that are from the fastigial nuclei on one side that cross the midline, before they go out via juxtarestiform body, to the other vestibular nucleus

Where are the 2 body representations in cerebellum?

1. Anterior lobe

2. Posterior lobe

What is the somatotopic organization of the cerebellum?

Two body representations —- one on anterior and posterior lobe each

Heads of the two bodies are pointed to one another with anterior lobe having an upside man

Somatotopic organization of the anterior lobe

Trunk and neck region of muscles are along the vermis

Distal limbs (feet + arms) are along intermediate zone

Somatotopic organization of the posterior lobe

NO trunk representation in vermis

Distal limbs (feet + arms) found in the intermediate zone

where are the distal limbs representation located on the cerebellum?

In all cases for the distal limbs are located in the intermediate zone of both the anterior and posterior zone

Where is the trunk representation located on the cerebellum?

The trunk is located in the vermis region of the anterior lobe ONLY.
it is not represented at the posterior lobe at all.

Describe the somatotopic representation of the lateral region of the cerebellum

No somatotopic organization of the lateral region.
Lateral region is involved in motor planning, it has no control over muscles

Function of the cerebellar pathways: Region → Primary role → Motor Pathways influenced

Lateral hemisphere

Lateral hemisphere → motor planning for extremities → LCST

Function of the cerebellar pathways: Region → Primary role → Motor Pathways influenced

Intermediate hemispheres

Intermediate hemispheres → Ongoing coordination of distal limbs and arms → LCST + Rubrospinal Tract

Function of the cerebellar pathways: Region → Primary role → Motor Pathways influenced

Vermis

Vermis → Proximal limb and trunk coordination in anterior lobe vermis region → ACST, Reticulospinal Tract, VST

Function of the cerebellar pathways: Region → Primary role → Motor Pathways influenced

Inferior Vermis + flocculonodular lobe

Inferior vermis + flocculonodular lobe → Balance and VOR → Medial Longitudinal Fasciculus (eye movement pathways)

Cerebellum acts as a comparator by detecting ____. It supplements and supports the ___ ___ cortex to perform ___, ___ movements

Cerebellum acts as a comparator by detecting errors. It supplements and supports the contrlateral motor cortex to perform smooth, coordinated movements

How is ongoing movement adjusted and modulated between cerebellum and cortex

Cerebellum receives:

1. Copy of efferent information regarding ongoing motor plans from the cortex via corollary discharge.

   1. Lets cerebellum know what the intended movement is

2. At the same time, cerebellum receives ascending sensory information of what actually happened ipsilaterally via external feedback

Cerebellum then:

1. Compares the intended goal movement against the actual motor response

2. Projects information back to motor area to make corrections

Ongoing mvmt is adjusted and modulated this way between cerebellum and cortex