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Summary of Lecture 3 VETS2011 Cerebellum

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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Summary of Lecture 3 VETS2011 Cerebellum

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  1. 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 Summary of Lecture 3VETS2011Cerebellum

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

  3. 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)

  4. 2. Vestibular neuron VOR circuit: 1. Vestibular hair cell 3. Oculomotor neuron Only 2 synapses. Purkinje cell modulates VOR reflex at vestibular neuron

  5. Trout Electric Fish

  6. Basic fish Electric Fish

  7. Forebrain Cerebellum

  8. Purkinje Cell. • Only output of cerebellum • GABAergic inhibition • 106 spine synapses • Spines modifiable by LTD • Climbing fibre“Punishes” co-active spine synapses • “Espalier “ shape enables tight packing in coronal plane despite huge sagittal arbour: gives “delay line”.

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

  10. 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.

  11. Interneurons. GolgiforGranulecells BasketandStellatefor Purkinje cells • Inhibitory • (GABA, glycine etc) • Diversity increases With cerebellar complexity (greatest variety in anthropoid primates)

  12. 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. 4 3 2 1

  13. 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

  14. Forebrain: Bilateral Single trial possible “Creative”; fraction of inputs LTP cAMP 2nd messager Error-prone ?Sleep needed Hindbrain:Midline Many trials needed “Stupid”: needs all inputs LTD cGMP 2nd messager Precise Corrected in waking state Declarative vs Procedural Memory

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