Static and Dynamic Postural Stability in Cerebral Palsy Children

Cerebral palsy (CP) concerns 2 children out of 1000 in the general population (SCPE 2002). It is the main cause of postural and motor deficits in children. During the past 20 years, the postural deficits exhibited by these children have been attributed to various factors : 1. neuromuscular functions 2. sensory integration 3. muscular-squeletic functions. The common point of all these studies is the existence of immature motor patterns, probably related to an inability to implement more elaborated and adapted motor patterns with respect the task to perform. CP children do not develop the characteristics of the plant grad locomotion. They exhibit a uniform muscular activation with a high level of co-activation. Locomotion is generally characterized by an increase of stretching reflexes at short latencies and by a low level of activation associated to a low modulation of gastrocnemius muscles.. These data also suggest that it is the control of the temporal rather than the spatial parameters of the head which are mainly altered in CP children. Even though static postural control and locomotion are considered as automatic processes, this control requires, however, a significant amount of attentional resources. Within this context, the amount of attentional resources which need to be solicited can provide information on two complementary dimensions. On one hand, on the level of automaticity of postural control and/or locomotion when subjects' attention is oriented toward another task. On the other hand, on the cognitive cost of postural control and/or locomotion, depending on children age, that is, as a function of their level of maturation and of the nature and importance of their sensory-motor deficits. When the amount of required attentional resources is reduced, postural control and/or locomotion is considered as automatic processes with a low cognitive cost. The dual task paradigm in which subjects have to simultaneously process a cognitive (e.g. Stroop task)