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This Article Full Text Full Text (PDF) All Versions of this Article: 99/6/2789    most recent 00487.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Haridas, C. Articles by Misiaszek, J. E. Search for Related Content PubMed PubMed Citation Articles by Haridas, C. Articles by Misiaszek, J. E.

Adaptation of Cutaneous Stumble Correction When Tripping Is Part of the Locomotor Environment

¹Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada; ²Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada; ³International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada; ⁴Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada; and ⁵Department of Occupational Therapy, University of Alberta, Edmonton, Alberta, Canada

Submitted 30 April 2007; accepted in final form 9 April 2008

We recently showed that cutaneous reflexes evoked by stimulating the superficial peroneal (SP; innervates foot dorsum) nerve are modulated according to the level of postural threat. Context-related modulation was observed mainly in contralateral (c) responses but not in the ipsilateral responses. This lack of effect on ipsilateral (i) cutaneous reflexes might have been caused by the general nature of the whole body perturbation. We therefore hypothesized that context-relevant mechanical perturbations applied to the dorsum of the foot by an instrumented rod at early swing during walking would produce differences in ipsilateral cutaneous reflex amplitudes, consistent with the functional relevance of the SP nerve in stumble correction responses. Subjects walked on a motorized treadmill under four conditions: 1) normal, 2) normal with mechanical perturbations at the foot dorsum, 3) arms crossed, and 4) arms crossed with mechanical perturbations at the foot dorsum. Electrical stimulation of the SP nerve was delivered at five phases of the step cycle, and cutaneous reflexes were compared between all conditions for each phase of the step cycle. Reflex responses were generally found to be modulated in amplitude during walking conditions in which mechanical perturbations were delivered, particularly in ipsilateral tibialis anterior (iTA), which showed a marked reduction in inhibition. The results indicated cutaneous reflexes in iTA and contralateral medial gastrocnemius (cMG) were influenced by the threat of a trip, induced by applying mechanical perturbations to the foot dorsum during walking. This task-related gating of cutaneous reflexes was not generalized to all muscles, thus suggesting a functional role in the maintenance of stability during locomotion.