Location specificity of plantar cutaneous reflexes involving lower limb muscles in humans

Abstract

It is known that cutaneous reflexes in human hand muscles show strong location-specificity dependent on the digit stimulated. We hypothesized that in lower leg muscles the cutaneous reflex following tactile sensation of the plantar surface of the foot is also organized in a location-specific manner. The purpose of the present study was to test this hypothesis. Middle latency reflexes (approximately 70-110 ms, MLR) following non-noxious electrical stimulation to different locations on the plantar foot were recorded from 16 neurologically intact volunteers (15 males, 1 female). Electrical stimulation was given to the fore-medial (f-M), fore-lateral (f-L) and heel (HL) regions of the plantar surface of the right foot while the subjects performed isometric dorsiflexion (tibialis anterior, TA), plantarflexion (soleus, Sol and medial gastrocnemius, MG), eversion (peroneus longus, PL) and knee extension (vastus lateralis, VL) while sitting and standing. In the Sol and MG, an excitatory response was observed following HL stimulation, which was switched to an inhibitory response following f-M or f-L stimulation (P < 0.001). A reciprocal pattern in contrast to Sol was observed in the TA. In the PL, MLR exhibited significant excitation following both f-L and HL stimulation, which, however, was switched to an inhibitory response following f-M stimulation (P < 0.001). Moderate inhibition of the MLR was seen in the VL for all stimulated positions. Systematic stimulation along the lateral side of the plantar foot demonstrated that the reflex reversal occurred around the middle of the plantar foot in the Sol and TA. In all muscles tested, the slope of the regression line between the magnitude of the MLR and background electromyographic activity significantly decreased during standing compared with sitting except for the PL following f-L simulation. These results suggest that reflex effects from cutaneous nerves in the plantar foot onto the motoneurons innervating the lower leg muscles are organized in a highly topographic manner in humans. The organization of these reflexes may play an important role in the alteration of limb loading and/or ground contact in response to tactile sensation of the plantar foot while sitting and standing.

History-dependent changes in the recovery process of the middle latency cutaneous reflex gain after ankle sprain injury

“…Cutaneous reflexes were evoked by applying electrical stimulation of rectangular pulses (1-ms duration) to the sural nerve, with trains of five pulses at 333 Hz (total duration, 13 ms, Nakajima et al 2006). The stimulus electrodes were placed on the lateral surface of the ankle just posterior to the lateral malleolus.…”

“…All subjects reported that the intensity of the electrical stimulation was not painful. The interstimulus interval was randomly altered (0.5-1.0 Hz) (Aniss et al 1992;Nakajima et al 2006).…”

Post-effect of forward and backward locomotion on body orientation in space during quiet stance

“…In addition, there was an overall trend for the CoP position during the walking cycles to be displaced more forward, along the foot sole, during WF than WB. Kinaesthesia and body orientation in space can be aVected by cutaneous aVerent input from the foot sole (Magnusson et al 1990;Bernard-Demanze et al 2004;Meyer et al 2004;Nakajima et al 2006). We would suggest that the opposite pattern in the direction of the foot-sole stimulation during WF and WB may also be related to the opposite body orientation in post-walking stance trials.…”

Reflex modulation during rhythmic limb movements in humans

“…Intralimb cutaneous reflexes have been demonstrated to possess task dependency (phasic locomotor vs. tonic maintained activity), intensity dependency (noxious vs. non-noxious stimulation), load dependency, phase dependency (swing vs. stance), and laterality dependency (ipsilateral vs. contralateral effects) [6][7][8] . The amplitude of cutaneous reflexes in both arm and leg muscles strongly depends on the location of the skin in which the stimulation was delivered (location specificity) [31][32][33] . These previous studies indicate that cutaneous reflexes are of functional importance for a variety of rhythmic movements for on-going activity in response to tactile sensation.…”