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Understanding Locomotion: Mechanisms, Patterns, and Central Pattern Generators in Movement

This lecture delves into locomotion, defining it as the activity that facilitates change in body location in external space. Examples include walking, running, swimming, and flying. Key characteristics such as velocity, stride length, and gait phases are discussed. The role of Central Pattern Generators (CPGs) in producing rhythmic movements is explored, with insights on how electrical stimulation can induce locomotion and modify gait. The lecture also covers the effects of external and internal factors on locomotion dynamics, offering a comprehensive overview of this vital physical activity.

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Understanding Locomotion: Mechanisms, Patterns, and Central Pattern Generators in Movement

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  1. Lecture 22: Locomotion Locomotion is an activity leading to a change in the location of the body in external space. Examples: walking, running, hopping, swimming, flying, crawling, etc. Important characteristics: • Velocity • Stride length • Relation between the support and swing phases • Relative timing of the extremities (gait)

  2. Locomotion: EMG Patterns During Human Walking

  3. Locomotion in Different Preparations

  4. Locomotion Induced by Stimulation of MLR

  5. Effects of Changing the Stimulation Strength

  6. The Locomotor Region and Strip

  7. Experiments on Decerebrate and Spinal Animals • Electrical stimulation of certain brain (and spinal) areas can induce locomotion. • Gait changes with the strength of the stimulation. • Locomotion and gait changes can also be induced by treadmill motion and by intraspinal drugs (GABA). • Fictive locomotion can be seen.

  8. Experiments on Decerebrate and Spinal Animals Graham Brown versus Sherrington: • The spinal cord is likely to contain one, two, or even four Central Pattern Generators (CPGs). • A CPG can be driven by descending and ascending signals. • It does not necessarily require either signal. • It can produce different gaits.

  9. Central Pattern Generator (CPG) • A CPG is a hypothetical structure in the central nervous system that can generate patterned (rhythmical) activity. • It can be driven by “higher” centers as well as by peripheral information. • Both sources of information can lead to gait changes.

  10. Homunculus A Simple Two-Half-Centers CPG

  11. “Higher centers” CPG Afferents a-motoneurons Central Pattern Generator

  12. CPG in the Lamprey Has Been Mostly Deciphered

  13. CPG in Humans: Starting Induced Locomotion

  14. CPG in Humans: Aftereffects of Spinal Stimulation

  15. CPG in Humans: Different Effects of Spinal Stimulation RHYTHMIC LEG MOVEMENTS WITH LOCOMOTOR SIGNS TYPICAL ATYPICAL CYCLE STRUCTURE INTERLIMB COORDINATION STEPPING RUN-LIKE INCOMPLETE CYCLE UNILATERAL STEPS BILATERAL STEPS ASYMMETRIC CYCLES OF LEFT AND RIGHT LEGS IN-PHASE STEPS WALK-LIKE DIFFERENT FREQUENCIES IN THE TWO LEGS UNUSUAL COORDINATION BETWEEN MOVEMENTS IN PROXIMAL AND DISTAL JOINTS ALTERNATING BETWEEN A FEW STEP CYCLES OF ONE LEG AND THE OTHER LEG

  16. CPG in Humans: Effects of Perturbations

  17. CPGs in Humans: A Hypothetical Structure

  18. Preprogrammed Reactions in Locomotion A B Stim Stim Surface

  19. Preprogrammed Reactions in Locomotion Corrective stumbling reaction: • Occurs during locomotion • Can be induced by a mechanical stimulus to the foot • Represents a complex pattern of EMG changes • Leads to a quick step over the obstacle

  20. Gait in Locomotion Relative timing: a programmed feature versus an emergent property

  21. Walking Trotting Galloping Gaits in Quadrupeds

  22. Relative Timing: Motor Programming

  23. Relative Timing: Dynamic Systems

  24. Relative Timing: Control + Coordination

  25. Preparation for Stepping

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