Neuromechanical Kinesiology

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Neuromechanical Kinesiology

• Lectures Day 1
• Introduction to motor pattern generation basic
  concepts
• Neurobiology of walking in mammals
• Context and memory-dependent regulation of
  stepping

UBC May 2008
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Video from "Planet Earth". BBC Television. 2006
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Neurobiology of locomotion some basic concepts

• Central pattern generation
• Sensory feedback for adapting movements
• to the immediate environment and/or state of
• the system
• 3. Descending command systems to initiate
  locomotion
• 4. Higher level signals for task selection,
  control of
• balance, navigation, object avoidance

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Concept 1
Central pattern generation
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A central pattern generator is a system
of neurons responsible for creating a particular
motor pattern in a nervous system deprived of all
sensory feedback regardless of whether all
aspects of the motor pattern of the intact animal
are produced or some part is missing Grillne
r Wallen 1985
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Charles Sherrington

• Concepts
• reciprocal inhibition
• chain reflexes

Sherrington 1910
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Thomas Graham Brown

• Concepts
• central rhythm generation
• half-centre organization

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Central rhythm generation in the spinal cord
Graham Brown 1911
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Central pattern generation in flying locust
Normal flight
Remove sensory feedback
Wilson 1961
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Neuronal circuit for feeding in crustacea
Stomatogastric ganglion crayfish
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Tritonia swimming
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Walking in the cockroach
Slow extensor motoneuron Ds
400ms
Loading
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Central pattern generation in cockroach walking
Electromyograms walking animal
Nerve recordings deafferented preparation
Pearson Iles 1971
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DOPA evokes fictive rhythm in spinal cat
Stimulate flexor nerve
Half-centre organization
FRA Flexor Reflex Afferents
Jankowska, Lundberg, et al 1967
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Some early contributions by Sten Grillner

• 1. Described weight-bearing stepping in
  hindlegs of chronic spinal cats
• Characterized fictive motor patterns in spinal
  cats (with Peter Zangger)
• Emphasized complexity of fictive motor pattern
  and promoted concept
• of central pattern generation in mammalian
  systems
• 4. Introduced concept of unit burst generators
• 5. Identified an major role of hip afferents in
  regulating the locomotor pattern

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Lamprey swimming - central pattern generation
Kandel et al 2000
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Neurobiology of lamprey swimming
Neuronal circuit
Computer simulation
Cellular and synaptic properties
Grillner Wallen 2002
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Full-scale simulation of lamprey swimming CPG
Video courtesy of Alexander Kozlov (unpublished)

• 3000 excitatory neurons (red)
• 2000 inhibitory neurons (blue)
• asymmetric rostral and caudal projections
• five compartment model of each neuron
• realistic membrane and synaptic conductances

Grillner 2006
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Concept 2
Sensory feedback for adapting movements to the
immediate environment and/or state of the system
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Sensory feedback maintains flight rhythm in the
locust
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Locust flight preparation
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Deafferentation modifies patterns of activity in
flight interneurons
Wolf Pearson 1988
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Phasic input from tegulae initiates wing
elevation
tegulae
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Walking and running in 10 month old infant
0.15 m/s
1.97 m/s
Movies from Jaynie Yang
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Sensory regulation of stance-to-swing transition
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Concept 3
Descending command systems to initiate locomotion
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Descending pathways from MLR to initiate walking
Stimulate mesencephalic locomotor region (MLR)
Shik, Severin Orlovsky 1966
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Reticulospinal neurons initiate swimming in the
lamprey
Rossignol et al. 2006
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Mechanisms for generating sustained activity in
reticulospinal neurons
Dubuc et al. 2008
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Concept 4
Higher level signals for task selection, control
of balance, navigation, object avoidance
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Task-dependent adaptation of locomotor pattern
level
down 45o
Modified from Smith et al. 1998
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Orientation responses of RS neurons in lamprey
Motor effects of single RS neurons
Deliagina et al 2008
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Pitch control system in lamprey
Circles Groups of reticulospinal neurons
activating motoneurons innervating the four
quadrants of the body (red excitation, green
inhibition)
Deliagina et al 2008
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Simulation of supraspinal control of swimming
Video from Orjan Ekeberg
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Commands from motor cortex modify leg movements
when stepping over objects
elbow flexor
motor cortex
Step over object
Neuron in motor cortex
Electromyogram in elbow flexor muscle
500ms
Drew 1986
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The basic concepts

• Central pattern generation
• Sensory feedback for adapting movements
• to the immediate environment and/or state of
• the system
• 3. Descending command systems to initiate
  locomotion
• 4. Higher level signals for task selection,
  control of
• balance, navigation, object avoidance

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Posture control in standing cat
Deliagina et al. 2008
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Supraspinal control of posture
Beloozerova et al 2003
Deliagina et al. 2008
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