Subjective Visual Vertical and Postural Performance in Healthy Children

Abstract

IntroductionVerticality is essential in our life, especially for postural stability. Subjective vertical as well as postural stability depends on different sensorial information: visual, vestibular and somesthesic. They help to build the spatial referentials and create a central representation of verticality. Children are more visuo-dependant than adults; however, we did not find any study focusing on how children develop their sense of verticality.MethodsWe studied two groups of subjects: 10 children (from 6 to 8 years) and 12 young adults. We recorded postural stability with a Techno Concept plateform and perception of subjective visual vertical in the following conditions: while adjusting the vertical in the dark or with visual perturbation, while fixating the vertical bar, and with eyes closed.ResultsChildren are more instable than adults in terms of postural parameters, and also while performing a double task, especially when no visual references are present. They also present a higher variability and lower accuracy than adults in reporting their perception of true vertical reference.DiscussionChildren might have limited attentional resources, and focus their attention on the more demanding task, corresponding to the U-shaped non-linear model.

Developmental study identifies the ages at which the processes involved in the perception of verticality and in postural stability occur

“…The absence of visual reference in the dark condition, or a perturbation of visual reference using optokinetic stimulation, can affect the allocentric reference frame used by the child to obtain a good perception of verticality. More specifically, Gaertner et al (14) showed that the accuracy of verticality at six to eight years old was scarce because children in that study were more dependent on visual information, so that the poor estimation of the SVV may have been caused by imperfect or incomplete integration of visual information. We have suggested that the scarce subjective visual vertical performance we observed in younger children could have been due to immaturity of the cortical and central areas involved.…”

“…A specially constructed subjective visual vertical (SVV) system was used to assess the visual vertical perception, which looked like an elongated clown, and was made from a phosphorescent tube and fluorescent cardboard (14). The clown was placed two metres away from the child, at eye level, and it could be moved to the left or to the right by the child using a remote control.…”

“…Thus, an internal model of verticality is imperative in healthy development, to build mental representation of the body (11). A study from our group (14) compared vertical perception during a postural task in young children aged from six to eight years and adults. To our knowledge, there have been very few studies to date that have explored children's vertical perception together with postural capability.…”

Maturation of Subjective Visual Vertical in Children

“…The role of sex has been advocated in inter individual differences of the short-term visual memory and visiomotor tasks (8,13). Evaluation of tasks involving visual capacity by the mirror box illusion test (14), mental rotation test (15), judgment of line orientation (16) also provide arguments in favor of sex differences in terms of visuomotor capacities.…”

“…Visuomotor tasks implicating the judgment of object or line orientation such as SVV appear to be under the influence of sex hormones (5)(6)(7). Women are reported to perform poorer in these tasks and to be more dependent on their visual context (8). Although many studies suggest that children have also a lower capacity in these tasks, due probably to the immaturity of their central nervous system, the influence of sex at early ages is unclear (8,9).…”