Motor control in Down syndrome: The role of adaptation and practice

A review of the literature on control of voluntary movements in Down syndrome is combined with original observations on the effects of extensive explanations and practice upon the motor performance in a variety of standardized single-joint motor tasks. After practice, Down syndrome subjects were able to perform fast targeted single-joint movements at speeds comparable with those demonstrated by unimpaired young adults. Down syndrome subjects were able to modulate their preprogrammed reactions in response to external perturbations. However, the patterns of modulation differed significantly from those seen in control subjects. A hypothesis is advanced that the differences between motor performance in DS and in the general population are reflections of adaptive reactions to the impaired decision-making learned during the lifetime in the conditions of a perpetually changing environment.