Touch and Balance During Walking

In this thesis the participation of tactile feedback from the hands in the control of balance was investigated. In Chapter 2, I characterized arm and leg reactions to unexpected perturbations delivered through the arms during walking. Perturbations applied at the hands resulted in early latency responses in arm muscles that were accompanied by activation of muscles in the leg when subjects were instructed to oppose the perturbations. Although no responses were observed in the arms when subjects were instructed to comply to the perturbations, most subjects presented responses in muscles of the leg. Activation of muscles in the legs were present during the comply condition even though the perturbations did not result in a balance disturbance. In Chapter 3, I investigated the effect of light touch sensory cues on the earliest postural reactions to balance disturbances during walking. The results of this study revealed that corrective responses in leg muscles to perturbations during walking are modulated by light touch. In particular, it was found that the effect of light touch on the corrective responses was more apparent when walking with the eyes closed compared to walking with the eyes open. Finally, in Chapters 4 and 5, I studied the effect of light touch on the gating of neural pathways transporting sensory information associated with the touch surface. The results of the study presented in Chapter 4 showed that segmental cutaneous afferent pathways are facilitated in the presence of touch if they transport sensory information from functionally relevant sensory cues (i.e. skin in contact with the surface). The results of the study presented in Chapter 5 showed that when tactile feedback associated with the touch surface is available interlimb sensorimotor pathways transporting sensory information from the skin in contact with the touch surface are facilitated. Altogether the results from this thesis revealed that sensory input from the hand can encode information describing the interaction between the body and the environment, hence plays a strong role in the control of balance.