Postural prioritization is differentially altered in healthy older compared to younger adults during visual and auditory coded spatial multitasking

Many daily activities require appropriate allocation of attention between postural and cognitive tasks (i.e. dual-tasking) to be carried out effectively. Processing multiple streams of spatial information is important for everyday tasks such as road crossing. Fifteen community-dwelling healthy older (mean age = 78.3, male = 1) and twenty younger adults (mean age = 25.3, male = 6) completed a novel bimodal spatial multi-task test providing contextually similar spatial information via separate sensory modalities to investigate effects on postural prioritization. Two tasks, a temporally random visually coded spatial step navigation task (VS) and a regular auditory-coded spatial congruency task (AS) were performed independently (single task) and in combination (multi-task). Response time, accuracy and dual-task costs (% change in multi-task condition) were determined. Results showed a significant 3-way interaction between task type (VS vs. AS), complexity (single vs. multi) and age group for both response time (p≤ 0.01) and response accuracy (p≤ 0.05) with older adults performing significantly worse than younger adults. Dual-task costs were significantly greater for older compared to younger adults in the VS step task for both response time (p≤ 0.01) and accuracy (p≤ 0.05) indicating prioritization of the AS over the VS stepping task in older adults. Younger adults display greater AS task response time dual task costs compared to older adults (p≤ 0.05) indicating VS task prioritization in agreement with the posture first strategy. Findings suggest that novel dual modality spatial testing may lead to adoption of postural strategies that deviate from posture first, particularly in older people. Adoption of previously unreported postural prioritization strategies may influence balance control in older people.