Cerebellum:

Describe lobes of Cerebellum and fissure associated

• Anterior Lobe

  • primary fissure

• Posterior Lobe

  • posterolateral (prenodular) fissure

• Flocculonodular Lobe

  • nodulus

  • midline flocculus (paired) — lateral

What are Lobules

• What are they?

• Composed of?

• Locations?

• Lobules:

  • Divides lobes of the cerebellum

• Composed of:

  • cortical ridges called folia.

• Locations:

  • Anterior Lobe: Lobules I-V

  • Posterior Lobe: VI-IX

  • floculonodular lobe: X

What are the functional divisions?

• Locations?

• Function?

• Vestibulo-cerebellum

  • (flocculonodular lobe)

  • Control of eye movements

• Spino-cerebellum

  • (vermis and paravermis)

  • Controls muscle tone and ongoing axial/limb movements

• Cerebro-cerebellum

  • (lateral hemisphere)

  • Role in planning and initiation of movements

  • Regulation of discrete upper limb movements

Describe the Cytoarchitecture

• Layers? (3)

• Types of neurons? (5)

Cytoarchitecture

• three layers:

  • Molecular Layer (outer)

  • Purkinje Cell Layer (intermediate)

  • Granule Cell Layer (inner)

    • ***Memorization: Move Please Grandma***

• five types of neurons:

  • principal neuron:

    • Purkinje Cell

  • intrinsic neurons

    • Basket (molecular layer)

    • Stellate (molecular layer)

    • Granule (granule cell layer)

    • Golgi (granule cell layer)

Describe the White matter Core

• Contains?

• Pairs of Nuclei? (4)

White Matter Core

• Contains:

  • Incoming and outgoing fibers

• Four Pairs of Deep Cerebellar Nuclei (gray matter)

  • Dentate

  • Emboliform

  • Globose

  • Fastigial

    • emboliform and globose = Interposed nuclei

Describe the Source of Input

• SC

• Vestibular System

• Cerebral Cortext

Describe the Somatotopic Organization of Inputs

Afferents:

• SC:

  • Spinocerebellar tracts (dorsal, ventral)

  • Cuneocerebellar tract

• Vestibular System:

  • Vestibulocerebellar tract

    • Direct to cerebellum (primary vestibulocerebellar fibers from vestibular apparatus)

    • Via vestibular nuclei (secondary vestibulocerebellar fibers)

• Cerebral Cortex

  • Cortico-pontocerebellar

  • Cortico-reticulocerebellar

  • Cortico-rubro-olivocerebellar*

  • Cortico-olivocerebellar*

  • NOTE: *Olivocerebellar input corresponds to the aforementioned longitudinal zones (corticonuclear projection zones)

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Somatotopic Organization of Inputs

• Anterior Lobe (one homunculus)

  • Leg anterior

  • Face posterior

• Posterior Lobe (two homunculi)

  • Face posterior

  • Legs anterior

• Trunk: midline

• Extremities: lateral

• Dorsal Vermis:

  • receives auditory and visual input,

  • overlaps w/ head region of homunculi

Describe the Fiber Systems

• 1. Transmits?

• 2.

• 3. Content? Termination? Function?

Fiber Systems:

• Climbing Fiber System:

  • Transmits olivocerebellar input

• Mossy Fiber System:

  • All other input except those listed below:

• Multilayered Fiber System

  • Content:

    • Hypothalamus

    • select cell groups w/in brainstem

  • Terminatation:

    • deep cerebellar nuclei

    • diffusely throughout cerebellar cortex

  • Function:

    • Decrease spontaneous and evoked activity of purkinje cells

      • (LC & Raphe n. , particularly)

Describe the Afferent/Efferent to Cerebellar Peduncles (Inferior,Middle,Superior)

Inferior (restiform/juxtarestiform body) (A/E)

• Olivocerebellar tract (major component)

• Dorsal Spinocerebellar tract

• Cuneocerebellar tract

• Reticulocerebellar & Cerebelloreticular tracts

• Vestibulocerebellar and cerebellovestibular tracts

• Arcuatocerebellar tract

• Trigeminocerebellar tracts (spinal and main)

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Middle (brachium pontis) — Afferent fibers

• —Pontocerebellar tract

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Superior (brachium conjunctivum) (A/E)

• Cerebellothalamic (dentatothalamic, interpositothalamic)

• Cerebellorubral (dentatorubral, interpositorubral)

• Ventral Spinocerebellar tract

• Trigeminocerebellar (mesencephalic)

Describe the Circuitry:

• Climbing

• Mossy Fibers

Climbing Fiber Circuit

• Climbing fiber → Purkinje cell + Deep Cerebellar nuclei

  • Excitatory (aspartate)

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Mossy Fiber Circuit

• Mossy fiber → Granule cell + Deep Cerebellar Nuclei

  • Excitatory (glutamate)

• Granule cell axons (parallel fibers) → Purkinje cell + Intrinsic neurons

  • Excitatory (glutamate)

• Intrinsic neurons → Purkinje cell

  • Inhibitory (GABA)

• Purkinje cell → Deep Cerebellar Nuclei

  • Inhibitory (GABA)

Describe how Climbing fiber (CF) input is highly focused

• Mech

• Function (2)

• Coincident activation?

Climbing fiber (CF) input is highly focused

• Mech:

  • 1 CF → 10 purkinje cells → 1000-2000 synapses with each cell

    • Note: Each purkinje cell receives input from only 1 CF.

• Function:

  • Produces Complex Spike in purkinie cell @ irregular intervals (low spike frequency)

  • Alters Purkinje cell sensitivity to parallel fiber input

    • CF input + parallel fiber-purkinje synapse → long term depression @ parallel Tiber- purkinje cell synapses,

Describe the Extensive divergence in mossy fiber- granule cell input

• Mech

• AP generation

• Function (2)

Extensive divergence in mossy fiber- granule cell input

• Mech:

  • Parallel fibers run along long axis of folium → hundreds purkinje cells.

    • Each purkinje cell: 100 -200 thousand parallel fiber synapses

• AP generation:

  • Requires summation of Parallel fiber input

• Function:

  • Produce Simple Spikes in purkinje cell (high spike frequency)

    • High Frequency → encode magnitude + duration of peripheral stimuli or central input.

  • Evokes high level of tonic activity in cerebellar cortex

Describe how Intrinsic inhibitory neurons increase the resolution of mossy fiber- parallel fiber input

• Stellate/Basket Cells:

  • Axons

  • Function

  • Result? What is this call

    • GIVE SIGNALS?

• Golgi Type II neurons

  • What happens to it?

  • Result?

  • GIVE SIGNALS?

• What does the Purkinje fibers do

Stellate/Basket Cells:

• Axons project laterally from Parallel Fibers’ Plane

• Function: Inhibits purkinje cells

  • → longitudinal patches of purkinje cell excitation bounded by Fences of Inhibition

    • (Center Surround Antagonism)

    • Gives Signal SPATIAL RESOLUTION

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Parallel fiber excitation of Golgi Type II neurons

Result:

• feedback inhibition to granule cell (& mossy fiber)

  • → Controls gain of granule cell input and shortens duration of parallel fiber bursts

  • → Gives Signal TEMPORAL RESOLUTION

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Purkinje Cells:

• Actively shape (inhibition) excitatory output of tonically active deep cerebellar nuclei

Describe the Inferior Olivary Nucleus (ION)

• Contains?

• Function? What happens when adaption is needed?

Describe the pathway of the two Recurrent olivo-cerebellar loops

ION:

• Contains:

  • spiny excitatory neurons

    • coupled via gap junctions

• Function: important role in motor learning

  • sends error signals related to motor commands or timing to the cerebellum

  • When Adaption is needed:

    • → climbing fiber activity Increases → complex spikes increases → progressive improvement

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Recurrent olivo-cerebellar loops:

• Olivocerebellar mesenencephalic-olivary loop

  • CF → (Directly + or Indirectly (purkinje) -) Deep Cerebellar N → (+) contra parvocellular red nucleus → (+) Ipsilateral ION via CTT → Increases synchrony of ION discharge

• Olivocerebellar nucleo-olivarv loop

  • Deep Cerebellar Nuclei → (-) contra ION → Decreases synchronous discharge of ION

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***NOTE: Deep cerebellar Nuclei: Glutamatergic (+) or GABAergic neurons (-)***

1. List out the cerebellar output (4)

2. Fastigial N Pathway:

3. Globose and Emboliform N. Pathway:

4. Dentate N. Pathway:

5. Flocculonodular lobe (vestibulocerebellum) Pathway

Cerebellar Output

• Spino-cerebellum

  • Medial Vermis → Fastigial n

  • Lateral Vermis → Lateral Vestibular n.

  • Paravermis → Globose and Emboliform n.

• Cerebro-cerebellum

  • Lateral Hemisphere→ Dentate n.

****Note: there is overlap between the spinocerebellum and the vestibulocerebellum. ****

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Fastigial N Pathway:

• → Vestibular bilateral) and Reticular Nuclei (Contra)

  • → SC (Medial Motor Systems)

    • vestibulospinal

    • reticulospinal

  • → nuclei involved in EOM (MLF)

    • Related to posterior vermal (occulomotor vermis) and vestibulocerebellar input to Fastigeal Nucleus

***Note: Axons also project to the contralateral superior colliculus (tectospinal tract) and ventrolateral thalamic nucleus (MI anterior corticospinal tract) via the uncinate fasciculus. These are functionally related to vermal input to the fastigial n. **

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Globose and Emboliform N. Pathway:

• → Red Nucleus (caudal, magnocellular portion)

  • → SC (rubospinal tract)

***Note: There are also projections to the ventrolateral thalamic nucleus (MI *lateral corticospinal tract).***

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Dentate N. Pathway:

• → Thalamus (VL)

  • → Cerebral Cortext

    • Primary Motor (MI) and Premotor Cortex

    • Prefrontal and Posterior Parietal Cortex

  • These cortical areas project back → cerebellum via pontine nuclei forming cerebrocerebellar loops.

***Note: there are also projections to the red nucleus (rostral, parvocellular portion). Rubroolivary projections originate here.***

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Flocculonodular lobe (vestibulocerebellum) Pathway

• → ipsilateral vestibular nuclei via juxtarestiform body

  • (sparse input to the lateral vestibular nucleus)

• → caudal fastigial nucleus via Nodulus purkinje cells

  • → vestibular nuclei (bilaterally)

    • EOM (MLf)

    • Balance (VST)

• Complex overlap with spinocerebellum

List out the Function of the cerebellum:

• Motor (2)

• Non-Motor (2)

  • Clinical?

Main Function (motor):

• Error detection and Movement correction

  • Matches Info for Cortext and Peripheary regarding movement

• Planning and Initiation of movement

  • Via Deep Cerebellar Nuclei discharge perior to movement

    • provides processed sensory info

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Non-Motor Function

• Autonomic:

  • Stimulation of vermis → cardiovascular function (e.g., carotid sinus reflex, BP) + pupillary diameter.

• May play a role in higher brain function, cognition, and behavior

• Clinical

  • Flushing and dialated pupils noted in patients with cerebellar lesions.

What are the symptoms of Cerebellar Disorder

• A: ataxia

  • Lack of coordination resulting in unsteadiness of movement

• H: hypotonia

  • Decrease in muscle tone — upon passive movement

• A: adiadochokinesia

  • Inability to perform rapid successive movements

• N: nystagmus

  • Rhythmic involuntary oscillatory movements of the eyes

• D —dsymetria

  • Can’t stop movement as the target IS approached

    • → overshoot of target

    • May be combined w/ kinetic tremor (see video)

• D —dyssynergia

  • Decomposition of movement

  • → Jerky and tremulous movement of extremity

• D —dysarthria (speech disturbance)

  • Slurred hesitant speech w/ inappropriate emphasis of pitch and loudness

Describe Tremor

• Kinetic Vs postural Vs titubation Vs Gate Ataxia (truncal ataxia)

Intention (kinetic) Tremor

• slow, course shaking movement during attempted voluntary movement

• amplitude increases during terminal portion of movement

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Static (postural) Tremor

• occurs during maintenance of position against gravity;

• oscilating movements of shoulders and arms when arms are outstretched.

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Titubation

• oscillatory movements of the head or trunk;

  • front→ back, side → side, or rotatory

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Gate Ataxia (truncal ataxia)

• wide based, clumsy, staggering gait,

  • similar to that seen with inebriation;

• Severe = difficulty sitting upright due to truncal instability

1. How can you test if someone has Cerebellar Disorders (3)

2. How can different lesions have different effects

1. Removal of pressure on flexed forearm → unchecked flexion

2. Tapping outstretched arm → oscillation of the arm around initial position,

   • ie., rebounding past the position.

3. Pendular reflexes:

   • patellar tendon reflex Tap → leg continuing to swing back and forth.

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Different Lesions Different Symptoms:

• Ipsilateral signs and symptoms with unilateral lesions

  • Due to double crossed circuitry

• Hemispheric lesions: limb

• Lesions of vermis: trunk

• Lesion of deep nuclei or SCP

  • more severe signs than lesion of cerebellar cortex

Describe Symptoms/ Area Affected Of:

• Midline Syndrome

• Lateral Syndrome

• Pancerebellar Syndrome.

Midline Syndrome:

• Symptoms:

  • Disequilibrium,

  • (truncal ataxia),

  • titubation

  • head tilt

  • Nystagmus,

  • saccadic dysmetria,

  • smooth pursuit deficits

• Involvement of:

  • floculonodular lobe and vermis (vestibulocerebellum and spinocerebellum)

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Lateral Syndrome:

• Symptom: A HAND3 Tremor

• Involvement of

  • intermediate and lateral zones (spinocerebellum and cerebrocerebellum)

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Pancerebellar Syndrome.

• Combination of midline + lateral (hemispheral) syndrome

• Symptom:

  • Bilateral signs of cerebellar dysfunction involving trunk, limbs, and eyes

Describe the Blood Supply

Superior Cerebellar Artery

• Rostral half of hemisphere and vermis;

• deep cerebellar nuclei;

• superior and rostral middle cerebellar peduncle;

• lateral tegmentum of rostral pons

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Anterior Inferior Cerebellar Artery

• Anterolateral part of caudal cerebellum (including flocculus);

• caudal middle cerebellar peduncle;

• lateral tegmentum of caudal pons

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Posterior Inferior Cerebellar Artery

• Caudal cerebellum (hemisphere, inferior vermis, tonsil and nodulus);

• choroid plexus of 4th ventricle;

• inferior cerebellar peduncle; dorsal lateral medulla (rostral part)