Visual occlusion effects on bipedal stance control in Chinese-speaking children with dyslexia

Visual processing of complex character configurations is especially challenging for Chinese-speaking children with dyslexia (CSCD). The purpose of this study was to compare the effects of visual occlusion on postural control between dyslexic and non-dyslexic Chinese-speaking children by examining their visual-perceptual capacity and movement coordination with scale measures. Sixteen dyslexic children (10 males and, 6 females, 9.46 ± 1.26 yrs) and sixteen non-dyslexic children (10 males and 6 females, 9.91 ± 1.18 yrs) were recruited from the campus in Taiwan. Motor and visual perceptual performance were assessed with the Movement Assessment Battery for Children, 2nd Edition (MABC-2) and the Test of Visual-Perceptual Skills, 4th Edition (TVPS-4). Root mean square (RMS) and sample entropy (SampEn) of center of pressure (COP) were characterized during a bilateral upright stance with eyes open (EO) and eyes closed (EC). The results showed significant group differences in six of the seven TVPS-4 subscales (P <.001-0.017) and one category of the MABC-2 (P =.006). In the EO condition, the children with dyslexia showed a greater RMS of COP specifically in the anterior-posterior (AP) direction than did the non-dyslexic children (P =.029). However, SampEn of COP in the two directions were not group dependent (P >.05). In the EC condition, RMS and SampEn of COP did not vary with group (P >.05). RMS of COP in the AP direction was negatively correlated with the sub-score of visual figure-ground in the TVPS-4 (r = -0.381, P =.031). In summary, postural control of Chinese-speaking children with dyslexia is more affected with eyes open than with eyes closed, and the effect is related to visual disturbance of the foreground and background.