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Factors determining segmental reflex action in normal and decerebrate cats
1Department of Clinical Neurosciences, University of Calgary, Faculty of Medicine, Alberta, Canada.
Journal of Neurophysiology
|November 1, 1990
Summary
Decerebration in cats increases the gain of the stretch reflex in ankle extensor muscles. This study found increased muscle spindle sensitivity, likely due to altered fusimotor neuron activity, explains this enhanced reflex.
Area of Science:
- Neuroscience
- Motor Control
- Physiology
Background:
- Decerebration in cats enhances the stretch reflex gain in ankle extensor muscles.
- The origin of this increased reflex and contributions from non-muscle afferents remain unclear.
Purpose of the Study:
- Identify the source of the enhanced stretch reflex after decerebration.
- Evaluate the role of afferents beyond ankle extensor muscles in the short-latency reflex.
Main Methods:
- Cats were trained for standing and force control tasks.
- Electromyogram (EMG) and electroneurogram (ENG) of ankle extensor muscles and nerves were recorded before and after decerebration.
- Controlled mechanical stretches and releases were applied to ankle extensor muscles.
Main Results:
- Post-decerebration, soleus (SOL) and lateral gastrocnemius (LG) muscle EMG bursts increased by 36-89% in area.
- Stretch-evoked LG-S nerve ENG bursts increased by 29-35% after decerebration.
- Muscle spindle sensitivity was found to increase post-decerebration.
Conclusions:
- The enhanced stretch reflex after decerebration is primarily due to increased muscle spindle sensitivity.
- Altered fusimotor neuron activity likely underlies the increased muscle spindle sensitivity.
- The study elucidates the neural mechanisms behind reflex modulation in the central nervous system.