NATURE AND NURTURE IN THE DEVELOPMENT OF POSTURAL CONTROL IN HUMAN INFANTS

Nowadays, the controversy on ''nature'' and ''nurture'' in motor devel opment focuses on the development of automatic motor patterns. The pre sent paper discusses this issue within the framework of a recent study on the effect of maturation and training on the development of postur al adjustments in sitting infants. This study revealed that already be fore the age of sitting without help, highly variable but direction-sp ecific muscle activation patterns are present. This suggests that post ural adjustments develop via an innate repertoire of primary direction -specific response patterns. The following developmental step consists of a decrease in muscle activation patterns, which results in selecti on of the most complete patterns of synergist activation. In accordanc e with Edelman's neuronal group selection theory, pattern selection tu rned out to be experience dependent, as it appeared to be guided by cu es on head stabilization and enhanced by daily balance training.