The Influence of Hearing on Posture

Maintaining upright posture requires integration of somatosensory, visual and vestibular information, and traditionally considered an automatic and effortless task. Recent research indicates that postural maintenance requires attention which interacts with other common tasks that share cognitive resources. This thesis investigates the influence of one such task, listening, on posture control and explores the novel idea that increased listening effort arising from hearing impairment uses extra attentional resources leaving less for posture control leading to an increased risk of positional or situational instability. A dual-task study to explore the relationship between listening and posture suggested that listening has a destabilizing effect on posture control. This effect was detected by mean velocity, a centre of pressure measure. To further understand this effect, the mechanisms underpins this relationship was studied using stabilogram diffusion analysis. The results suggested that open-loop and closed-loop strategies were utilised to maintain upright posture. This relationship was further investigated under simulated hearing loss conditions, and the results revealed increased postural sway and longer open-loop times before switching to closed-loop mechanisms. The deterioration of postural performance whilst listening may be explained by the idea that working memory has limited resource capacity to execute tasks, and that both tasks here requires attention and are competing for cognitive resources. Therefore, when the simulated hearing loss was introduced, it exacerbated this effect suggesting that performance was compromised due to the raised listening effort. It was concluded that mean velocity was sensitive to changes in postural sway resulted from performing a concurrent listening task. It was also concluded that stabilogram diffusion analysis would provide a comprehensive understanding of the postural strategies individuals adopted to maintain erect posture under normal and simulated hearing loss listening conditions.