Interaction between Visual and Proprioceptive Analyzers in Vertical Posture Control

The CNS can precisely assess the spatial position of the human body only by simultaneously processing and integrating the visual, proprioceptive, and vestibular inputs. Postural stability data make it possible to estimate changes taking place in the function of analyzers involved in the maintenance of the upright posture. The vertical posture stability was assessed in healthy children and children with spastic diplegic cerebral palsy from their postural responses to the presentation of single optokinetic or somatosensory stimuli. The visual analyzer was found to play a significant role in maintaining the upright position under natural gravity conditions in healthy children. A single exposure of the proprioceptive system to variable forces directed with the gravity of the earth (vertical) decreased the contribution of the visual analyzer. Healthy children maintained the upright position relying on the direction of movement of the optokinetic stimuli, which, however, produced no effect on the maintenance of posture in the patients. A hypothesis is proposed that prenatal or early postnatal CNS lesions decrease the contribution of phylogenetically newer brain structures to the regulation of upright posture.