Interaction between different sensory cues in the control of human gait

Abstract

This experiment investigates the interaction of different sensory cues in the control of propulsive forces in human gait which in turn allow the body's forward progression to be regulated. The aim of this work was to determine how optic flow and leg-somatosensory feedback interact in this control. We therefore determined whether the responses to sinusoidal perturbations of optic flow were accentuated when leg-somatosensory feedback was modified by varying the support resistance. Subjects walked on a treadmill which was driven by their own locomotor activity (1) with a sinusoidal variation of optic flow velocity, (2) with a sinusoidal variation of support resistance which modified leg-somatosensory information and (3) with both visual and leg-somatosensory modification at different frequencies. The response of the subject was measured as changes in speed and propulsive power. The response to sinusoidal perturbations of optic flow was found to be increased and time delayed when visual perturbations are coupled with support perturbations in comparison with the response observed with visual perturbations only. This result shows the influence of leg-somatosensory feedback on the weighting of optic flow. Inversely, it was also found that the motor response to support perturbation was different when the flow was congruent (i.e., corresponding to the subject's virtual speed) and when it was not. This latter result shows the influence of optic flow on the weighting of leg-somatosensory feedback. The interaction between optic flow and leg-somatosensory feedback argues in favor of a multimodal sensory control of propulsive forces. This multimodal sensory control would be based on all the sensory feedback and all their mutual sensorial interaction. Therefore, the modification of one sensory input modifies not only this input but also the integration of the other inputs.

Modulation of Walking Speed by Changing Optic Flow in Persons with Stroke

“…Results of the present study demonstrate that walking speed is modulated out-of-phase with OF speed in healthy subjects, which is consistent with previous studies [6][7][8], despite the fact that expanding OFs were simulated by a meaningful and rich virtual environment in the present study. Previous research used gratings composed of dots, spots or diamonds oscillating to form contracting and expanding OFs [6][7][8].…”

“…Previous research used gratings composed of dots, spots or diamonds oscillating to form contracting and expanding OFs [6][7][8]. The observed non-volitional changes in gait speed induced by changes in OF speed in our healthy age-matched controls, although consistent, were of small magnitude.…”

“…OF is a source of visual information that can be used to control heading direction [2][3][4] and speed [5][6][7][8] of walking, as it provides information about the direction and speed of self-motion with respect to the environment. Studies in healthy individuals have shown that changing OF speed modulates walking speed while walking on a self-paced treadmill [6][7][8][9]. During walking, visual (OF) and proprioceptive information about self-motion are normally congruent.…”

Agency, gait and self-consciousness

“…The results confirmed that motor correction always preceded conscious awareness of a mismatch. Varraine et al (2002) demonstrated partly analogue results for treadmill walking. In this experiment participants unconsciously adjusted their walking characteristics, force or speed, for about 6 s even though they were explicitly asked to report these changes as soon as they arose (although this delayed awareness may result from a difference in the paradigm as perturbations were only increased gradually and no visual feedback was available to the participants).…”

Stabilization and mobility of the head and trunk in vervet monkeys(Cercopithecus aethiops) during treadmill walks and gallops

“…Evidence continues to accumulate that the vestibular apparatus functions as an inertial navigational system (Berthoz and Pozzo, 1994;Dunbar et al, 2004;Mayne, 1974;Pozzo et al, 1990) within the stable platform of the head (Pozzo et al, 1990), and is sensitive to the gravito-inertial acceleration vector (Imai et al, 2001). Together, these visual and vestibular cues can also determine locomotor velocity (speed of approach) and acceleration (Bertin et al, 2000;Prokop et al, 1997;Telford et al, 1995;Varraine et al, 2002). During walks, by contrast, a stabilized trunk can provide information about spatial orientation by combining signals from the vestibular apparatus and neck proprioceptors (Mergner et al, 1983(Mergner et al, , 1991(Mergner et al, , 1992, and from proprioceptors (Jacobs et al, 1985;Mittelstaedt, 1988;Taylor and McCloskey, 1990) and nonproprioceptive receptors (Mittelstaedt, 1995(Mittelstaedt, , 1996(Mittelstaedt, , 1997Vaitl et al, 1997) in the trunk itself.…”