1. Cerebellum

• Comprises 10% of total brain volume but contains over 50% of the neurons
  • Highly folded cortex
  • The major neuron type is Purkinje Cell
• Attached to the Pons of the Brain Stem
• Cerebellum Hemispheres are linked up by Vermis
  • other structures are:
    • Primary Fissure
    • Declive
    • Nodulus
    • Lingula

A

• Fluorescent dye injected in a living Purkinje Cell, the major and only output neuron type in Cerebellum

B

• Section through the Cerebellar Cortex where Purkinje Cells express a yellow fluorescent reporter while Granular Cells a blue reporter

Functions of Cerebellum

<aside> 💡 Cerebellum is the organ of Agility - 敏捷 灵巧

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• Movements:
  • Balance and Posture (equilibrium)
    • Inner ear
  • Muscle Tone and Coordination
    • Spinal Cord - Proprioception
  • Motor Learning
    • Motor Cortex

Lesion and Impairment

example: Lesion in Left Cerebellar Hemisphere

• Cerebellum lesions cause deficiencies in performing simple motor tasks
  • Simple motor tasks need to be executed consciously
  • Pre-programmed motor patterns can no longer run automatically
• Cerebellum is involved in the fine-tuning of movements

Functional Regions

• Cerebellum consists of Anterior, Posterior and Flocculonodular Lobe
  • Anterior Lobe - Tone
  • Posterior Lobe - Coordination
  • Flocculonodular Lobe - Balance
• If look in anther way, Cerebellum consists of Cerebrocerebellum, Spinocerebellum and Vestibulocerebellum (directly associated to their function and linked Deep Cerebellar Nuclei)

Inputs

• Corticopontine Inputs: Inputs to lateral hemispheres of Cerebellum are provided by Corticopontine Projections - to Cerebrocerebellum and Vestibulocerebellum
• Spinal and Trigeminal Inputs: Inputs to intermediate parts of the hemispheres and Vermis - to Spinocerebellum
• Vestibular Inputs: Vermis and Flocculonodular Lobe process Vestibular Inputs
• Visual Inputs: Central part of the Vermis receives Visual Inputs

Outputs

• Motor Planning:
  • Output from Cerebrocerebellum (Lateral Hemisphere) through Dentate Nucleus to Premotor and Motor Cortices
• Motor Execution:
  • Outputs from Spinocerebellum
    • through Fastigial Nucleus of the Vermis to Medial Descending Systems
    • through Interposed Nucleus of the Intermediate Hemisphere to Lateral Descending Systems
• Balance and Eye Movement:
  • Output from Vestibulocerebellum (Flocculonodular Lobe) to Vestibular Nuclei

Somatosensory Input

<aside> 💡 Somatosensory Input lead to a Fractured Somatotopic Map

</aside>

• Somatotopic maps of body surface in cerebellum contains at least 2 maps of the body - Fractured
• Several subdivisions of Cerebellum contain Somatotopic Maps
  • facilitates the control or fine-tuning of motor programmes
  • almost all motor programmes involve more than just one part of the body

2. Neurons and Circuits within the Cerebellum

Neurons