10) Central Pattern Generators

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Why study control of motor patterns?
Movement is important –all animals do it, existence depends on it for: Respiration Reproduction Finding food and shelter Avoiding predation Eating etc.
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Medical relevance?
Movement disorders Spinal paralysis through disease or injury Parkinson’s Disease Sudden Infant Death Syndrome.
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Why is Studying motor control is a good way to analyze how neural circuits and individual neurons control behaviour?
Motor behaviours are easy to define & measure, Easy to identify & study general features of operation of neural circuits, Can study how behaviours are triggered & controlled, Are they preprogrammed? How is switching between prog.s achieved? coordinat
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Invertebrates of particular interest
Lobster/crab stomatogastric ganglion and control of pyloric and gastric mill rhythms (only 32 neurons) Crayfish –swimmerettes and escape behaviour Clione –swimming Tritonia –swimming/escape behaviours Leech –locomotion Locust –flight, kicking
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Advantages of invertebrate models?
V simple NS–only a few 1000’s of neurons per ganglion. Relatively small no. of types of neurons & only small no. of each type involved. Possibility of in vivo/semi-intact preps where neurons can be recorded during the motor behaviour while happening
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Experimental disadvantages of Invertebrate Preps?
Neurons may have complex morphology -it may not be possible to record close to the postsynaptic and integrative sites. Molecular/genetic techniques not developed for many invertebrate species (Drosophila being the big exception –but this has 1stprob
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Biological disadvantages of Invertebrate Preps
Signalling systems somewhat different from vertebrates (transmitters, receptors etc). Organization of the nervous system very different from vertebrates –generality of results?
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Vertebrate Models?
Cats –of big historical importance, many of the key concepts have arisen from cats. Lamprey –swimming Frog tadpoles –swimming Lower mammals –rat and mouse now starting to be used Advantage of mouse is use of gene knock-out techniques
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Advantages of Vertebrate Preps?
Results of direct applicability to the human condition. Basic organisation of the nervous system shared. Easier to exploit molecular genetic techniques and genomics (esp. true for mouse). Better pharmacological agents available,better Ab,cDNA probes
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Disadvantages of Vertebrate Preps?
Complexity –many neurons and many types of neurons.(Lower vertebrates eg.lamprey & tadpole offer major advantage of reduced complexity).Great redundancy –100’s to 1000’s of each type of neuron. How do you manipulate?Harder to record in situ.Anaesthes
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How do we study motor pattern generation?
We have to be able to relate activity of neurons & circuits to behaviour=impossible without first defining the behaviour. Kinematic studies –the sequence of movements, information about efficiency and power Getting to the neural machinery(musclesnerv
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What is the Reflex Hypothesis?
Rhythmic movements generated through a sequence of reflexes
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What is The Central Hypothesis?
Central circuits exists which have the right connectivity and properties to generate in the absence of any sensory feedback the correct sequence of muscle contractions and movements.
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Role of Central Pattern Generators?
Rhythmic motor behaviours are indeed centrally generated and are controlled by circuits commonly called Central Pattern Generators
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What evidence is important in correct generatorion and coordination of behaviour?
Removal of sensory feedback can alter the motor pattern, Imposed feedback can entrain the centrally generated pattern
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Types of edge cells?
One type has contralateral axons and is inhibitory The other type has ipsilateral axons and is excitatory
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Modern view of Cnetral Pattern Generators?
Central circuits definitely exist but integrate sensory inputs and higher command centres
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Medical relevance?

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Movement disorders Spinal paralysis through disease or injury Parkinson’s Disease Sudden Infant Death Syndrome.

Card 3

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Why is Studying motor control is a good way to analyze how neural circuits and individual neurons control behaviour?

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Preview of the front of card 3

Card 4

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Invertebrates of particular interest

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Card 5

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Advantages of invertebrate models?

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