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Modulation of human cutaneous reflexes during rhythmic cyclical arm movement
1Neurophysiology Laboratory, Faculty of Physical Education & Recreation, University of Alberta, Edmonton, Canada. pzehr@ualberta.ca
Experimental Brain Research
|December 29, 2000
Summary
Cutaneous reflexes in rhythmic upper limb movements are mainly influenced by background muscle activity, not solely by movement phase. This differs from lower limb locomotion, suggesting distinct control mechanisms for arm cycling.
Area of Science:
- Neuroscience
- Human Movement Science
- Motor Control
Background:
- The modulation of cutaneous reflexes during rhythmic upper limb movements is not well understood.
- Central Pattern Generators (CPGs) are hypothesized to drive rhythmic arm movements, similar to leg locomotion.
Purpose of the Study:
- To investigate the organization and pattern of cutaneous reflex modulation during rhythmic upper limb movements.
- To test the hypothesis that cutaneous reflex amplitude is independent of electromyographic (EMG) muscle activation level (phase-dependent modulation).
Main Methods:
- Recorded EMG from eight upper limb muscles during cyclical arm movements.
- Evoked cutaneous reflexes using electrical stimulation of the superficial radial nerve.
- Analyzed reflex modulation in relation to movement cycle and background EMG activity.
Main Results:
- Rhythmic muscle activity and reciprocal activation of antagonist muscles were observed.
- Cutaneous reflexes were modulated with the movement cycle for most muscles.
- Reflex modulation was strongly correlated with background EMG amplitude.
Conclusions:
- Cutaneous reflexes during rhythmic upper limb movements are primarily modulated by background muscle activity.
- Unlike lower limb locomotion, phase-dependent modulation was limited, suggesting different neural control strategies.