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Motor System

Motor System. http://www.rci.rutgers.edu/~aglass/M&ASyllabus.htm. Question. How do you teach a one-armed man to clap?. Two Kinds Motor Movements. Reflexes Voluntary Motor Movements (Actions). Two Kinds Motor Movements. Reflexes

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Motor System

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  1. Motor System http://www.rci.rutgers.edu/~aglass/M&ASyllabus.htm

  2. Question • How do you teach a one-armed man to clap?

  3. Two Kinds Motor Movements • Reflexes • Voluntary Motor Movements (Actions)

  4. Two Kinds Motor Movements • Reflexes • Simplest reflex arc involves sensory neuron and motor neuron which causes muscle contraction • Voluntary Motor Movements (Actions)

  5. Reflex Arc

  6. 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)

  7. Reflexes Involuntary movement: may be a single ballistic movement (eye blink) or a motor sequence if a central pattern generator in the spinal cord is activated (infant swim reflex) Conditioned innate fast response to (novel) stimulus routinely preceding unconditioned Stimulus (Rescorla-Wagner model) Unconditioned innate fast response to unconditioned stimulus

  8. Functions of Unconditioned Reflexes Maintain vestibular- ocular pupil dilation muscle contraction spindles, tendons, joints, skin Approach ear pricking salivate None goose bumps Avoid eye blink

  9. Two Kinds Motor Movements • Reflexes • Voluntary Motor Movements (Actions)

  10. 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

  11. 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)

  12. Cortical Motor System

  13. 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

  14. Planning A Grasp Four 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).

  15. 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.

  16. Constructing A Motor Program (Povel & Collard, 1982)

  17. Motor System for Voluntary Movements (Actions) • Planning • Performance • Motor cortex and basal ganglia aim and initiate body movement • Cerebellum programs muscle movements

  18. Cortical Motor System

  19. Basal Ganglia

  20. Motor & Somatosensory Maps

  21. 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.

  22. Execution: Motor subsystems • Locomotion • Motor cortex • Manipulation • Motor cortex • Vocalization • Broca’s area • Visual Fixation and tracking • Frontal eye fields

  23. 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

  24. 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.

  25. 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

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