Visual and proprioceptive control of arm movements : studies of development and dysfunction

Abstract: The aim of this dissertation was to examine the role of sensory information for control of goal-directed arm movements in children. The role of visual and proprioceptive information on the target for end point accuracy was examined in normal 4- to 12-year- old children (Study I), and in children with motor impairments (Study II). Accuracy in pointing with the unseen hand was found to improve rapidly during the age period tested, with the most pronounced development taking place in the preschool years. Visual specification of the target was superior to proprioceptive specification for all age groups tested. The performance of children with motor impairments was more variable than that of the non-impaired children, and this effect was most pronounced when visual information about the target was unavailable. The importance of visual information for controlling the transport and handling part of reaching movements were examined in normal 6- to 8-year-old children (Study III), and in children with developmental coordination disorders (Study IV). Object handling required visual information on both target and hand. For the transport phase of the movement visual information on target was sufficient, and sight of hand did not improve performance. The young children were relatively more impaired than the older children when lacking adequate visual information. The children with developmental coordination disorders responded to the withdrawal of visual information in a similar way to that of the normally developed children. A discontinuity at 7 years of age in the development of perceptual control of pointing movements, observed in Study I, was further investigated and confirmed in study V. In this study the ability to control movements visually and prorioceptively was also investigated and found to develop in parallel rather than one being a prerequisite for the other.