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The control of limb geometry in cat posture
F Lacquaniti1, M Le Taillanter, L Lopiano
1Istituto di Fisiologia dei Centri Nervosi, C.N.R., Milano, Italy.
The Journal of Physiology
|July 1, 1990
Summary
Quadrupedal stance relies on limb geometry control, not center of mass projection. Cats maintained limb posture despite added weight, indicating primary control of limb configuration for stability.
Area of Science:
- Neuroscience
- Biomechanics
- Animal Locomotion
Background:
- Understanding postural control in quadrupeds is crucial for biomechanics and neuroscience.
- Previous hypotheses suggested control of center of mass, joint torques, or limb geometry during stance.
Purpose of the Study:
- To investigate which variable (center of mass, joint torques, or limb geometry) is primarily controlled during quadrupedal stance.
- To differentiate between competing hypotheses of postural control mechanisms.
Main Methods:
- Cats were trained to stand on a tiltable platform, with forces and joint positions recorded.
- Load cells measured paw contact forces, and the ELITE system tracked limb joint kinematics.
- External loads were applied to assess responses in center of mass, joint torques, and limb posture.
Main Results:
- Limb axes and contact force vectors remained aligned vertically, with minimal variation in center of mass projection and limb geometry across tilt angles.
- Applied external loads shifted the center of mass but did not alter limb posture, despite significantly increasing forelimb joint torques.
- No adaptation in postural behavior was observed over 24 hours of continuous loading.
Conclusions:
- Limb geometry, specifically the configuration of the limbs, is the primary controlled variable in quadrupedal stance.
- Findings support hierarchical control models and provide insights into the body schema during postural adjustments.