Cutaneous afferents from human plantar sole contribute to body posture awareness

Abstract

We investigated whether the tactile information from the main supporting areas of the foot are used by the brain for perceptual purposes, namely body posture awareness and body representation in space. We applied various patterns of tactile stimulation to one or both soles of unmoving and blindfolded subjects by a 60 micro-vibrator tactile matrix set in a force platform. The perceptual effects of the stimulation were assessed through a 3D joystick handled by the subjects. All subjects reported illusory perceptions of whole-body leaning. Both orientation and amplitude of these perceptions depended on the stimulation pattern. Additional kinesthetic illusions sometimes occurred along the longitudinal axis of the body. We conclude that foot sole input contributes to the coding and the spatial representation of body posture.

A novel approach to mechanical foot stimulation during human locomotion under body weight support

“…The tools we developed can be applied to other dynamic conditions (including microgravity, see for instance Khusnutdinova, Netreba, and Kozlovskaya (2004), Layne, Forth, and Abercromby (2005)) during walking or standing or even when restrained on the bed (Selionov, Ivanenko, Solopova, & Gurfinkel, 2009;Shapkova & Schomburg, 2001). The tactile information from the main supporting areas of the foot is also used by the brain for perceptual purposes and can evoke strong kinesthetic illusions (Roll et al, 2002) and activations of somatosensory areas and superior parietal lobes (Chernikova et al, 2007). A direct (touch) contact of bipeds with an external world occurs constantly via the foot so that it represents an important element of our interaction with surroundings.…”

“…Since the tactile information from the foot may evoke contact-or load-related sensations (Roll, Kavounoudias, & Roll, 2002), we also asked participants for their perception of the stimulus. All participants reported prominent sensations of an extra foot pressure during walking.…”

Postural Responses to Various Frequencies of Vibration of the Triceps Surae and Forefoot Sole during Quiet Standing

“…Such vibration stimulation at 60-150 Hz induces backward leaning of the body if the subject is standing with their eyes closed, and the response latencies are longer than those of reflexes. This has been interpreted to mean that sensory information with vibration induces the illusionary perception of forward leaning, and backward leaning occurs as a compensatory response via the sensory reference frame (Fujiwara et al, 2003;Gurfinkel & Levic, 1991;Roll, Kavounoudias, & Roll, 2002;Lackner & Levine, 1979).…”

Vertical illusory self-motion through haptic stimulation of the feet

“…To be more exact, Roll and colleagues [10] performed a study of whether tactile information from the main supporting areas of the foot influences body posture awareness and body representation in blindfolded subjects who are physically restrained at the shoulder and hip levels. While all ten participants experienced illusory full-body leaning, seven also reported kinesthetic illusions along the longitudinal axis of the body, that is, they experienced upward movement.…”

“…Roll et al [10] do not disclose detailed information about the signals used to drive the haptic stimulation. Our experiment remains relatively explorative in nature.…”