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NEUROSCIENCE |
1 Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC, Canada
2 Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
3 Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
4 Human Neuromechanics Laboratory, University of Michigan, Ann Arbor, MI, USA
It has been proposed that different forms of rhythmic human limb movement have a common central neural control (‘common core hypothesis’), just as in other animals. We compared the modulation patterns of background EMG and cutaneous reflexes during walking, arm and leg cycling, and arm-assisted recumbent stepping. We hypothesized that patterns of EMG and reflex modulation during cycling and stepping (deduced from mathematical principal components analysis) would be comparable to those during walking because they rely on similar neural substrates. Differences between the tasks were assessed by evoking cutaneous reflexes via stimulation of nerves in the foot and hand in separate trials. The EMG was recorded from flexor and extensor muscles of the arms and legs. Angular positions of the hip, knee and elbow joints were also recorded. Factor analysis revealed that across the three tasks, four principal components explained more than 93% of the variance in the background EMG and middle-latency reflex amplitude. Phase modulation of reflex amplitude was observed in most muscles across all tasks, suggesting activity in similar control networks. Significant correlations between EMG level and reflex amplitude were frequently observed only during static voluntary muscle activation and not during rhythmic movement. Results from a control experiment showed that strong correlation between EMG and reflex amplitudes was observed during discrete, voluntary leg extension but not during walking. There were task-dependent differences in reflex modulation between the three tasks which probably arise owing to specific constraints during each task. Overall, the results show strong correlation across tasks and support common neural patterning as the regulator of arm and leg movement during various rhythmic human movements.
(Received 2 April 2007;
accepted after revision 24 April 2007;
first published online 26 April 2007)
Corresponding author E. P. Zehr: Rehabilitation Neuroscience Laboratory, PO Box 3010 STN CSC, University of Victoria, Victoria, BC, Canada V8W 3P1. Email: pzehr{at}uvic.ca
This article has been cited by other articles:
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  E. P. Zehr, M. Klimstra, K. Dragert, Y. Barzi, M. G. Bowden, B. Javan, and C. Phadke Enhancement of Arm and Leg Locomotor Coupling With Augmented Cutaneous Feedback From the Hand J Neurophysiol, September 1, 2007; 98(3): 1810 - 1814. [Abstract] [Full Text] [PDF]
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