Download - Motor System
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Motor System
http://www.rci.rutgers.edu/~aglass/M&ASyllabus.htm
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Question How do you teach a one-armed
man to clap?
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Two Kinds Motor Movements Reflexes Voluntary Motor Movements
(Actions)
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Two Kinds Motor Movements Reflexes
Simplest reflex arc involves sensory neuron and motor neuron which causes muscle contraction
Voluntary Motor Movements (Actions)
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Reflex Arc
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Two Kinds Motor Movements Reflexes
Reflex arc Other reflexes may involve
complicated movements generated by central pattern generators in spinal cord.
Hormonal response May become conditioned to novel inputs.
Voluntary Motor Movements (Actions)
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Involuntary movement: may be a single ballistic movement(eye blink) or a motor sequence if a central pattern
generatorin the spinal cord is activated (infant swim reflex)
Unconditionedinnate fast responseto unconditioned
stimulus
Conditionedinnate fast responseto (novel) stimulusroutinely preceding
unconditionedStimulus
(Rescorla-Wagnermodel)
Reflexes
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Avoid
eye blink
Maintain
vestibular-ocular
pupil dilation
musclecontractionspindles,tendons,
joints, skin
Approach
ear pricking
salivate
None
goosebumps
Functions of Unconditioned Reflexes
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Two Kinds Motor Movements Reflexes Voluntary Motor Movements
(Actions)
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Voluntary Movements Require
Perception of target Awareness of location of movable
body part Ability to aim movement of body part Ability to detect errors and re-adjust,
(use feedback) Ability to use feedback to control
movement of body part
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Motor System for Voluntary Movements (Actions) When a familiar voluntary action is
performed: Planning: a representation of a body-part
posture or sequence of postures is retrieved Cortical areas
Parietal cortex Premotor and supplementary motor cortex
Performance: muscle movements are initiated to move the body-part(s) into the represented posture(s)
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Cortical Motor System
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Planning An Action Parietal cortex
Neurons respond to both visual and tactual inputs
Input used in activating and selecting among plans
Premotor and supplementary motor cortex Activation and selection of plans Mirror neurons respond when the same
action is performed or observed
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Planning A GraspFour steps in planning a grasping action. Representations of grasping hand postures are retrieved from memory (top panel). The hand posture providing the closest fit to the target is selected (second panel). Representations of arm extensions are retrieved from memory (third panel). The arm extension providing the best fit with the grasp posture and its location is selected (bottom panel).
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Hierarchical Organization Complex patterns of movements
can be built up hierarchically by combining posture plans into a single motor program. Advantage of large program: speed.
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Constructing A Motor Program (Povel & Collard, 1982)
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1 2 3 4 5 6Position in Sequence
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Motor System for Voluntary Movements (Actions)
Planning Performance
Motor cortex and basal ganglia aim and initiate body movement
Cerebellum programs muscle movements
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Cortical Motor System
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Basal Ganglia
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Motor & Somatosensory Maps
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Damage: Motor and Somatosensory Cortex Damage to motor cortex (map)
causes hemiplegia, normal voluntary movement of body part corresponding to map damage is not possible.
If limb is severed a phantom limb results because the body map is unchanged.
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Execution: Motor subsystems Locomotion
Motor cortex Manipulation
Motor cortex Vocalization
Broca’s area Visual Fixation and tracking
Frontal eye fields
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Motor System for Voluntary Movements (Actions)
Planning Parietal cortex Premotor and supplementary motor
cortex Performance
Motor cortex and basal ganglia aim and initiate body movement
Cerebellum programs muscle movements
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Cerebellum A motor program produces smooth
movements by specifying a precisely timed sequence of muscle contractions.
Vestibulocerebellum contains reflexes for maintaining balance and coordinating eye movements (vestibular-ocular reflex).
Spinocerebellum & neocerebellum turn motor plans into motor programs.
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Motor system is heterarchical and redundant Redundant sources of plans
Premotor (external) Supplementary Motor (internal)
Redundant sources of limb information Visual Kinesthetic
Redundant ways of executing and controlling limb movements Motor cortex Basal Ganglia Cerebellum