Cerebellum: Anatomy and Function

• Cerebellum aids in the precision of motor function

Learning Objectives

• Comprehend the cerebellum's function in motor activities and how its deficits differ from basal nuclei deficits
• Determine the anatomical and functional parts of the cerebellum such as as spinocerebellum, cerebrocerebellum, vestibulocerebellum
• Ascertain the input and output pathways for the spinocerebellum, cerebrocerebellum, and vestibulocerebellum
• Understand the relationships between purkinje cells, deep cerebellar nuclei, climbing fibers, and mossy fibers

Case Study

• A 44-year-old male experiences clumsiness in his right arm and veers to the right when walking
• He has a shaking in his right hand when reaching, symptoms started six months ago and are worsening
• The patient staggers to the right during tandem walking and nearly pokes his eye when touching is finger to his nose with his eyes closed
• There is a notable tremor in his right hand and fine, lateral oscillatory eye movements are observed, indicating a hemispheric lesion

Cerebellum Function

• Coordinates motor functions that result in motor precision
• Regulates the velocity of movement, force, duration, timing when to start or stop, and trajectory
• Facilitates procedural memory involved in tasks like riding a bike, driving a manual car, and playing tennis

Cerebellum Anatomy - Views

• Anterior lobe is visible in the anterior view
• Primary fissure indicated on top of the anterior lobe in the midsagittal view
• Nodulus observed in the posterior view
• Flocculus, cerebellar hemispheres, horizontal fissure observed in the ventral view

Cerebellum Anatomy - Zones

• Vermal zone resides in the middle
• Anterior lobe located towards the front
• Vestibulocerebellum zone observed in the front bottom
• Hemispheric zone observed in the lateral zone
• Posterolateral fissure observed in the posterior view
• Flocculonodular lobe observed in the bottom posterior view

Cerebellum Anatomy - Homunculus

• Vermis controls proximal and axial musculature
• Hemisphere controls distal limbs, hands, feet, and arms

Deep Cerebellar Nuclei

• Fastigial nucleus observed in the center
• Globose nucleus observed above the vermis
• Emboliform nucleus next to the dentate
• Dentate nucleus to the side of the nucleus
• Globose and emboliform combine to form the interposed nucleus

Pathways Through Cerebellum

• Spinal cord feeds into the spinocerebellum which then passes through the middle of the vermis which is beside the Paravermal
• Cerebral cortex feeds into the Cerebrocerebellum through the lateral
• Vestibular receptors feed into the vestibulocerebellum from the inner ear through the flocculonodular lobe
• Fastigial intermediate nucleus then passes to to vermis
• Interposed nuclei then passes to Paravermal
• Dentate Nucleus then passes to lateral
• Vestibular Nuclei pass to flocculonodular lobe

Cerebellum - Connections

• Receives information from the cerebral cortex about planned movement
• Receives proprioceptive input from the body allowing to know balance and head position
• It also Plays a role in motor learning and timing
• Passes information from the cerebral cortex via the thalamus
• Provides information about balance, head position, motor learning and timing and proprioceptive input
• Sends motor control signals to adjust posture and muscle tone
• Information is used to compare intended vs actual movement allowing for corrections to motor systems providing smoother movement
• The cerebellum needs to know intended movement coming from the cortex including actual movement from proprioceptive and vestibular input

Vestibulocerebellum - Flocculonodular lobe

• Controls balance and equilibrium, impacting anti-gravity muscles
• Controls coordination of eye and head movements

Vestibulocerebellum - Input and Output

• Input from the vestibular system
• Output to vestibular nuclei
• Vestibulospinal tracts
• Medial longitudinal fasciculus interconnects cranial nerves III, IV, VI
• The vestibulocerebellum contributes to eye movement via cranial nerves

Spinocerebellum Functions:

• Occurs in Vermal and Paravermal areas and helps to adjust movements based on proprioceptive feedback
• Includes axial and proximal muscles specifically trunk and limbs
• Posture and muscle tone using extensors

Spinocerebellum - Input and Output:

• Input from Dorsal and ventral spinocerebellar tracts, cuneocerebellar, trigeminocerebellar tracts
• Output to Vestibulospinal and reticulospinal tracts

Cerebrocerebellum Function

• Occurs in lateral hemisphere and prepares to predict force, velocity, trajectory
• Precise coordination of motor commands with proprioceptive and vestibular input especially arm and hand movements

Cerebrocerebellum - Input and Output

• Input from Corticopontocerebellar tract is a copy of motor orders

• Olivocerebellar tract controls procedural learning

• Dentorubrothalamic tract controls feedback to motor cortex

• Output to Rubrospinal tracts

• Inhibitory cells form the molecular layer

• Purkinje cells form the Purkinje layer, are inhibitory, and have output to deep cerebellar nuclei

• Granule cells form the granular layer

• Deep cerebellar nuclei receive input from mossy fibers, climbing fibers and Purkinje cells, output is variable

Cortico-Olivocerebellar Pathway- Inferior Olivary Nucleus

• Controls procedural learning, reinforcing motor skills
• Practice makes perfect

Overview of Cerebellar Connections

• Instructions processed from cerebrum with corticopontocerebellar copies of commands

• Proprioceptive information (spinocerebellar) allows for position sense from spinal cord

• Postuture, balance (vestibulocerebellar)

• Feedback to cerebrum (dentorubrothalamic)

• Extrapyramidal output; Rubrospinal, reticulospinal, vestibulospina

• Connections are schematic not anatomically precise

• Clinical representation is ipsilateral

• Motor cortex is the composer and the cerebellum is the conductor

Cerebellum and Basal Ganglia Similarities - Lesions

• Both basal ganglia and the cerebellum influence the motor cortex via the thalamus(VL)
• Both modify or adjust motor commands
• No paralysis results from lesions, only impairments occur.
• Neither runs directly to the muscles

Cerebellum and Basal Ganglia Differences

• Basal ganglia have a "permissive" function including inhibiting involuntary movements, and facilitates volunatry movements
• Cerebellum has an "execution" function
• Plans movements ordered by motor cortex
• Provides corrective feedback to motor cortex
• "Fine tunes" ongoing movements

Explore the cerebellum's role in motor precision and its distinct deficits compared to basal nuclei deficits. Investigate the anatomical and functional divisions: spinocerebellum, cerebrocerebellum, and vestibulocerebellum. Understand input/output pathways and the relationships between Purkinje cells, deep cerebellar nuclei, climbing fibers, and mossy fibers.