Summary of Lecture 3 VETS2011 Cerebellum

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Summary of Lecture 3VETS2011Cerebellum

• Demo of VOR in owl VOR plasticity
• World record cerebellum Electric fish
  nanosecond timing
• Summary of structure and function in cerebellum
• Time-to-place conversion
• Adaptive plasticity of VOR (Owl, wet head
  example)
• Contrast procedural learning with declarative
  memory

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Procedural Memory

• Gain of reflexes (e.g. VOR)
• Conditioned reflexes (e.g. eye blink)
• Skilled sequences (e.g. cycling, typing)

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Vestibulo-Ocular Reflex (VOR)

• Fastest reflex in brain
• Operates perfectly without cerebellum
• (i.e. same conditions)
• But gain adaptation requires cerebellum
• (i.e. as conditions change, such as growth,
  ageing, muscle strength, oxidative damage etc)

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• VOR circuit
• 1. Vestibular hair cell

2. Vestibular neuron
3. Oculomotor neuron
Only 2 synapses. Purkinje cell modulates
VOR reflex at vestibular neuron
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Trout Electric Fish
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Basic fish
Electric Fish
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Forebrain
Cerebellum
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• Purkinje Cell.
• Only output of cerebellum
• GABAergic inhibition
• 106 spine synapses
• Spines modifiable by LTD
• Climbing fibrePunishes
• co-active spine synapses
• Espalier shape enables tight packing in
  coronal plane despite huge sagittal arbour gives
  delay line.

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• Excitatory Inputs.
• Mossy fibre to
• granule cells to
• parallel fibres to
• spine synapses
• on Purkinje cells
• Vast combinations
• provide the sensory
• context

Sensory context
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• Climbing fibre
• Covers whole
• dendritic tree of
• Purkinke cell
• All-or-nothing acitvation
• Co-activation of climbing
• fibre and parallel fibre
• Leads to LTD of the
• parallel fibre synapse.

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• Interneurons.
• Golgi for Granule cells
• Basket and Stellate for Purkinje cells
• Inhibitory
• (GABA, glycine etc)
• Diversity increases
• With cerebellar complexity
• (greatest variety in
• anthropoid primates)

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• Time-to-Place Conversion
• Purkinje cells along beam
• of parallel fibres
• e.g. 10 m/sec gives 10 mm/msec
• or 10 mm/msec.
• So a 10 mm spacing
• between Purkinje cells
• allows a time resolution
• of 10 msec.
• Electric fish achieve
• nanosecond timing with
• larger, faster beams.

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• Time-to-Place Conversion
• Purkinje cells along beam
• of parallel fibres
• e.g. 10 m/sec gives 10 mm/msec
• or 10 mm/msec.
• So a 10 mm spacing
• between Purkinje cells
• allows a time resolution
• of 10 msec (humans).
• Electric fish achieve nanosecond
• timing with larger, faster beams.

msec
30
20
10
0
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Declarative vs Procedural Memory

• Forebrain Bilateral
• Single trial possible
• Creative fraction of inputs
• LTP
• cAMP 2nd messager
• Error-prone
• ?Sleep needed

• HindbrainMidline
• Many trials needed
• Stupid needs all inputs
• LTD
• cGMP 2nd messager
• Precise
• Corrected in waking state