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Somatosensory unit input to the spinal cord during normal walking
Canadian Journal of Physiology and Pharmacology
|July 1, 1981
Summary
This study reveals how different sensory receptors in cats, including cutaneous mechanoreceptors and muscle afferents, signal movement and muscle tension during locomotion. Findings suggest varied neural strategies for sensing stretch and contraction in different muscle types.
Area of Science:
- Neuroscience
- Locomotion Biomechanics
- Sensory Physiology
Background:
- Understanding sensory feedback is crucial for motor control.
- Previous research has characterized some afferent classes, but comprehensive functional patterns remain unclear.
Purpose of the Study:
- To investigate the activity patterns of various large myelinated afferent classes during locomotion in freely walking cats.
- To elucidate the functional roles of different sensory receptors in sensing joint position, muscle tension, and stretch.
Main Methods:
- Chronic extracellular recordings from single afferent units in freely walking cats.
- Analysis of neural activity in relation to limb kinematics and muscle activity.
Main Results:
- Cutaneous mechanoreceptors exhibit high sensitivity and regular, modality-predictable activity.
- Knee joint afferents respond to locomotion but are influenced by more than just joint angle.
- Golgi tendon organs reflect active muscle tension.
- Muscle spindle afferents show complex patterns, suggesting differential roles in sensing stretch and contraction based on muscle type and movement.
Conclusions:
- Sensory afferents provide rich information about locomotion, with distinct roles for cutaneous, joint, and muscle receptors.
- Muscle spindles likely employ different control strategies (fusimotor bias) for extensor and flexor muscles to encode stretch and preserve activity during dynamic contractions.
- Bifunctional muscles may contain spindles with varied functional properties.