Effects of visual deprivation on intra-limb coordination during walking in children and adults.

Following the laws of planar covariation, intersegmental coordination is defined with respect to the vertical and heading direction. This vertical reference can be estimated using multisensory information, amongst others visual cues play a role. In the past it was already shown that visual deprivation and/or perturbation of visual information largely affect gait kinematics. The goal of this study is to investigate the impact of visual deprivation on intra-limb movement coordination. Children aged between 3 and 11 years and young adults are included in this study to investigate age-related differences in the visual control of locomotion. Intersegmental coordination was tested under two different conditions: full vision (FV) and no vision (NV). Heading direction and walking speed were taken into account. A significant interaction effect was observed between visual condition and age for walking speed. Between age groups, no differences are observed in the FV condition but in the NV condition children walk significantly slower than adults. This shows that the relative importance of visual information is age dependent. Between age groups significant differences were found in heading direction. Coordination was characterized using the planar covariation technique, by constructing thigh versus shank and shank versus foot angle-angle plots and by cross-correlation function analysis. Regardless of the presence or absence of visual information, the planarity index remains high, indicating that the laws of planar covariation hold in the absence of visual afferent information. On the other hand, the shape of the gait loop does show significant differences between FV and NV conditions. Changes in the shape of the gait loop are primarily determined by changes in the coupling between the thigh and shank elevation angles. The coupling between the shank and foot elevation angles is dependent upon walking speed and does not differ between FV and NV conditions. Between age groups significant differences are observed in covariation plane orientation.