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Forelimb reflexes modulated by tonic neck positions in cats
Pflugers Archiv : European Journal of Physiology
|May 18, 1978
Summary
Neck position significantly influences forelimb reflexes in cats. Body movements modulate deep radial nerve (DR) and ulnar nerve (ULN) reflexes, demonstrating a clear somatosensory-motor integration.
Area of Science:
- Neuroscience
- Motor Control
- Somatosensory System
Background:
- Tonic neck positions are known to influence posture and movement.
- The specific impact of neck afferents on monosynaptic reflexes in the forelimb requires further elucidation.
Purpose of the Study:
- To investigate how tonic neck positions modulate monosynaptic forelimb reflexes in cats.
- To determine the extent and characteristics of this modulation.
Main Methods:
- Monosynaptic reflexes of the deep radial nerve (DR) and ulnar nerve (ULN) in the forelimb were recorded in cats.
- Cats underwent controlled lateral and sagittal body (neck) displacements with the head fixed.
- Effects were analyzed across varying degrees of body displacement and with or without intact cerebrum and cerebellum.
Main Results:
- Lateral body flexion facilitated ipsilateral DR reflexes and inhibited contralateral ULN reflexes, with opposite effects for contralateral movement.
- Dorsiflexion increased DR reflexes and strongly inhibited ULN reflexes; ventriflexion produced opposite effects.
- Modulation began at ~5 degrees of displacement and increased with angle, independent of cerebrum/cerebellum, decreasing along the spinal cord.
Conclusions:
- Tonic neck positions exert significant, direction-dependent modulation on monosynaptic forelimb reflexes.
- This neck-to-forelimb reflex modulation is a spinal mechanism, decreasing in influence caudally along the spinal cord.