Abstract
Purpose: :
Developmental dyslexia is a primitive reading disorder. However, other signs are associated such as perception, motor and attention deficiencies. The purpose of this study was to assess the coupling between postural and saccadic control in children with developmental dyslexia.
Methods: :
Eleven healthy male subjects (mean age 13.9 years±1.1) and seven dyslexic subjects (5 males and 2 females, mean age 12.5 years±1.7) were included. Subjects stood on a force platform and were asked to fixate a visual target. In the prosaccadic task (reflex task) subjects followed the target with their eyes. In the antisaccadic task (cognitive task), the instruction was to make an eye movement as fast as possible in the opposite direction of the target motion.
Results: :
Prosaccadic taskControl subject: no impact on postural stability was found.Control versus dyslexic: experimental condition×group interaction was found for the direction of the vector of displacement of the center of pressure (VdCoP) and standard deviation on y axis (SDy, p=0.02 and p=0.05 respectively). The SDy increased significantly in the dyslexic group when the target moved to the left (p=0.02).Antisaccadic taskControl subject: the SDy and the path length increased significantly (p=0.03 and p=0.02 respectively). Moreover, the type of saccade (prosaccadic and antisaccadic tasks) influenced these two parameters (p=0.005 and p=0.02 for SDy and path length respectively).Control versus dyslexic: the SDy increased in the dyslexic group (p=0.03). Experimental condition×group interaction was found only for the direction of the VdCoP (p=0.05). However, no influence of the type of saccade was noted.
Conclusions: :
Healthy children showed only low postural performance when introducing antisaccadic task while reflexive prosaccades and antisaccades altered postural stability in dyslexic children. The increase of the attention load could affect other tasks such as postural control suggesting global attention deficiency. Given that the total attention capacity is limited, attention load assigned to reading could be decreased.
Keywords: eye movements: saccades and pursuits • visual development: infancy and childhood • vision and action