1. Chapters 12 Motor System – Cerebellum
Chris Rorden
University of South Carolina
Norman J. Arnold School of Public Health
Department of Communication Sciences and Disorders

2. Function of Cerebellum
Error Control Device - Monitor, Quality Control
Monitors outputs to muscles from motor cortex and sensory signals from receptors
Compares the efferent project plan with execution at motor action site
Considers related factors and makes adjustments

3. 50% of brain’s neurons, 10% of volume
Cerebellum
50% of brain’s neurons, 10% of volume
Can change movements as necessary
E.G. Walking or talking
Does not reach conscious awareness
Muscle synergy or coordination monitored
Important in running, speaking - all fluid movements

4. tentorium cerebelli
"tent of the cerebellum"
dura mater that separates the cerebellum from the inferior portion of the occipital lobes.

5. Posterior Cranial Fossa
Fossa is a depression or cavity in the bone
Cerebellum, pons, and medulla oblongata sit in the Posterior cranial fossa

6. Located dorsal to pons and medulla
Cerebellar Anatomy
Seen from feet
Located dorsal to pons and medulla
In posterior fossa under tentorium cerebelli
Lobes
Floccular Nodular(small fluffy mass)
Anterior
Posterior
Anterior lobe (H)
Posterior lobe (I)

7. Longitudinally separated into hemispheres and cortices
Flattened Cerebellum
Longitudinally separated into hemispheres and cortices
Median (Vermal)
Vermis=worm
Paramedian (Paravermal
Lateral

8. Cerebellum Paramedian Primary Median Fissure Posterior Superior
Horizontal
Fissure
Prepyramidal Fissure
Posterolateral Fissure

9. Cerebellar Nuclei (Nuclei = deep cluster of neurons)
Dentate nucleus
Largest, communicates through cerebellar peduncle
Carries information important for coordination of limb movements (along with the motor cortex and basal ganglia)
Emboliform nucleus (medial side of the nucleus dentatus)
Regulates movements of ipsilateral extremity
Globose nucleus
Fastigial nucleus
Regulates body posture
Is related to the flocculo nodular lobe

10. Dentate Nucleus
Dentate
Nucleus
Pontine
Projections
Superior
Cerebellar
Peduncle
Pons

11. Somatotopic Organization
Tactile information
Ipsilateral anterior lobule
Bilateral paramedian lobules
Cerebral Cortex and Cerebellum have similar representations
Motor representation
Same area as sensory mapping
May have auditory and visual processing

12. Transverse Cerebellar Regions
Floccular nodular lobe (Archicerebellum )
Oldest, related to vestibular part of VIII
Regulates equilibrium through vestibulospinal tract
Anterior lobe (Paleocerebellum)
Rostral to Primary Fissure
General Sensory Receptors
Concerned with muscle tone and walking
Posterior lobe (Neocerebellum)
Newest and Largest, Receives afferent projections from contralateral sensorimotor cortex
Projects to contralateral motor cortex
Functions in coordination of fine and skilled movements

13. Longitudinal Cerebellar Regions
Vermis
Contributes to body posture
Paravermal region
Regulates movements of ipsilateral extremities (e.g. walking)
Lateral Zone
Regulates skilled movements of ipsilateral extremity (e.g. tying your shoe)

14. Cerebellar Connection
Three Peduncles
Inferior – afferent: mediate sensorimotor input to the cerebellum
Middle – afferent: same as above
Superior – efferent: transmit output from the cerebellum to the brainstem and on to the thalamus, motor cortex, and spinal cord
Varied afferents to Cerebellum :
spinal cord
brainstem
motor cortex
Afferenet:Efferent Ratio = 40:1
For each going from cerebellum to body, 40 coming in

15. Afferent Pathways (Inferior)
Vestibulocerebellar Tract
Info From Semicircular Canals Through Inferior Peduncle
Maintains Upright Posture
Dorsal Spinocerebellar Tract
Info From Reticular Nuclei (involved in regulation of sleep, respiration, heartbeat, etc.)
Unconscious Proprioception From Muscle Spindles, Golgi Tendons and Tactile Receptors

16. Afferent Pathways (Inferior 2)
Reticulocerebellar Tract
Info From Cerebral Cortices, Spinal Cord, Vestibular Complex, and Red Nucleus
Olivocerebellar Tract
Info From Spinal Cord Through Olivary N to Contralateral Cerebellar Hemisphere
Source of Climbing Fibers for Direct Input to Cerebellum
Cuneocerebellar Tract
Mediate Proprioception From Upper Limbs and Neck

17. Afferent and Efferent Projections
Thalamus
Red nucleus
Superior Cerebellar
Peduncle
Middle Cerebellar
Peduncle (pontocerebellar
fibers)
Inferior Cerebellar Nucleus
(olivocerebellar fibers)

18. Afferent Pathways (Middle)
Info From Pontine Nuclei From Opposite Cerebral Cortex, Visual and Auditory Inputs
To Opposite Cerebellar Hemisphere

19. Arise From Cerebellar Nuclei
Efferent Pathways
Arise From Cerebellar Nuclei
Dentate nucleus
Emboliform nucleus
Globose Nucleus
Through Superior Cerebellar Peduncle to
Red Nucleus (Brainstem)
Thalamus
Motor Cortex

20. Structured in Three Parallel Layers
Cerebellar Cortex
Structured in Three Parallel Layers
Molecular
Purkinje
Connecting Surface and Deep Cerebellar Nuclei
Source of All Efferent Fibers
Cerebellar Cortex
Granular
Have Mossy Fiber Axons to Purkinje Axons

21. Clinical Considerations
Signs of Dysfunction
Impaired Muscle Synergy
Reduced Muscle Tone
Evident in Skilled Tasks
Ataxia
Lack of Order and Coordination in Activities
Slow Movement (Bradykinesia)
Mild Muscular Weakness (Asthenia)
Asynergia
Speech difficulties (Ataxic Dysarthria)
affects respiration, phonation, resonance and articulation, but most pronounced in articulation and prosody.

22. Clinical Considerations 2
Dysdiadochokinesia
Clumsiness in Alternating Movements
Tapping, Speech Sound
Dysarthria
Ataxic Dysarthria
Scanning Speech
Slurred and Disjointed Speech
Dysmetria
Error in Judgment of Range and Distance of Target
Undershooting or Overshooting

23. Clinical Considerations 3
Intentional Tremor
Accessory Movement During Volitional Task
vs. Parkinson’s Disease Where Tremor Lessens During Volitional Movement
Hypotonia
Reduced Resistance to Passive Stretch
Rebounding
Inability to Predict Movement
Cannot Hold Back Movement
Disequilibrium
Unsteady Gait, Body Wavering

24. Cerebellar Pathologies
Cerebrovascular Accident (CVA)
Thrombotic, embolic or hemorrhagic
Vertebrobasilar Artery
Toxicity
Chronic Alcoholism
Progressive Cerebellar Degeneration
Friedrich's Ataxia: Autosomal Recessive Heredity Degenerative Condition
Combined Sensory and Motor Dysfunctions