Sense of Balance
Higher-level Adaptive And Cognitive Systems
Higher-level systems, such as the cerebellum, are responsible for integrating information from the three sensory systems, and then adapting postural responses to meet the demands of changing sensory conditions. In the 1980s and 1990s a number of laboratories examined the ability of healthy and balance-impaired older adults to adapt senses to changing conditions during quiet stance using posturography testing. Results showed that healthy active older adults were not significantly different from young adults in amount of body sway except in conditions where both ankle joint inputs and visual inputs were reduced or absent. In these conditions, half of the older adults lost balance on the first trial for these conditions, requiring the help of an assistant. However, most of the healthy older adults maintained balance on the second trial within these two conditions. This suggests that they are capable of adapting postural responses to meet changing sensory conditions, but only with practice in the condition. Balance-impaired older adults had a larger percentage of falls in any condition with misleading somatosensory cues. Thus, a problem contributing to balance-impairment in many older adults is the inability to adapt responses to changing sensory conditions.
Studies in the 1990s began to determine if attentional requirements of postural control increase in older adults, by using a dual task paradigm in which older adults are asked to balance while performing a second cognitive task (e.g., a math task). Results indicate that balance is more attentionally demanding in older than younger adults and is highest in balance-impaired older adults. Attentional demands increase as the complexity of the balance task increases (e.g., responding to a slip).