title: Regionally distinct cutaneous afferent populations contribute to reflex modulation evoked by stimulation of the tibial nerve during walking.
abstract: During walking, cutaneous reflexes in ankle flexor muscle [tibialis anterior (TA)] evoked by tibial nerve (TIB) stimulation are predominantly facilitatory at early swing phase but reverse to suppression at late swing phase. Although the TIB innervates a large portion of the skin of the foot sole, the extent to which specific foot-sole regions contribute to the reflex reversals during walking remains unclear. Therefore, we investigated regional cutaneous contributions from discrete portions of the foot sole on reflex reversal in TA following TIB stimulation during walking. Summation effects on reflex amplitudes, when applying combined stimulation from foot-sole regions with TIB, were examined. Middle latency responses (MLRs; 70-120 ms) after TIB stimulation were strongly facilitated during the late stance to mid-swing phases and reversed to suppression just before heel (HL) strike. Both forefoot-medial (f-M) and forefoot-lateral stimulation in the foot sole induced facilitation during stance-to-swing transition phases, but HL stimulation evoked suppression during the late stance to the end of swing phases. At the stance-to-swing transition, a summation of MLR amplitude occurred only for combined f-M&TIB stimulation. However, the same was not true for the combined HL&TIB stimulation. At the swing-to-stance transition, there was a suppressive reflex summation only for HL&TIB stimulation. In contrast, this summation was not observed for the f-M&TIB stimulation. Our results suggest that reflex reversals evoked by TIB stimulation arise from distinct reflex pathways to TA produced by separate afferent populations innervating specific regions of the foot sole.
authors.affiliation: Department of Integrative Physiology, Kyorin University School of Medicine, Tokyo, Japan; tsunakaj@ks.kyorin-u.ac.jp.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nakajima
authors.affiliation: Department of Integrative Physiology, Kyorin University School of Medicine, Tokyo, Japan; Division of Sports and Health Science, Chiba University, Chiba, Japan; United Graduate School of Education, Tokyo Gakugei University, Tokyo, Japan;
authors.forename: Shinya
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: Division of Sports and Health Science, Chiba University, Chiba, Japan; United Graduate School of Education, Tokyo Gakugei University, Tokyo, Japan; Faculty of Business and Information Sciences, Jobu University, Gunma, Japan;
authors.forename: Genki
authors.initials: G
authors.lastname: Futatsubashi
authors.affiliation: Division of Sports and Health Science, Chiba University, Chiba, Japan; Health Sciences University of Hokkaido, School of Rehabilitation Science, Hokkaido, Japan;
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ohtsuska
authors.affiliation: Division of Sports and Health Science, Chiba University, Chiba, Japan; Laboratory of Signal Processing and Motor Control, College of Physical Education, University of Brasília, Brasília, Brazil; Biomedical Engineering Laboratory, Escola Politécnica da Universidade de São Paulo, Telecomunicações e Controle, University of São Paulo, São Paulo, Brazil;
authors.forename: Rinaldo A
authors.initials: RA
authors.lastname: Mezzarane
authors.affiliation: Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada; Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada; Human Discovery Science, International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada; and.
authors.forename: Trevor S
authors.initials: TS
authors.lastname: Barss
authors.affiliation: Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada; Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada; Human Discovery Science, International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada; and.
authors.forename: Taryn
authors.initials: T
authors.lastname: Klarner
authors.affiliation: Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada; Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada; Human Discovery Science, International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada; and Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada.
authors.forename: E Paul
authors.initials: EP
authors.lastname: Zehr
authors.affiliation: Division of Sports and Health Science, Chiba University, Chiba, Japan; United Graduate School of Education, Tokyo Gakugei University, Tokyo, Japan;
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Komiyama
mesh_terms: D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D000704:Analysis of Variance; D004576:Electromyography; D005260:Female; D005528:Foot / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D012867:Skin / Q000294:innervation*; D012879:Skin Physiological Phenomena; D013979:Tibial Nerve / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: bipedal walking; cutaneous reflex; foot sole; humans; reflex reversal