Influence of visual cues on localization of acoustic sound sources in old adults

Abstract

Localization accuracy of stationary acoustic objects is reduced as people grow older. While it is known that this reduction can be caused by many age-related declines in the peripheral sensory system, at central cortical levels as well as in cognitive processes, it is not known how much localization performance is influenced by concurrent congruent and/or incongruent spatial information from a different sensory system, e.g., vision. In the present study we examined localization accuracy of young and old adults to acoustic stimuli that were presented simultaneously to a visual stimulus that was either spatially congruent or spatially disparate (by ±5°/±10°/±15°) in acoustic free field. The acoustic reference position was presented at frontal (9°), para-frontal (30°), and lateral (64°) positions. To infer how strongly the visual cue interacted with the auditory stimulus a unification task was examined. Here, acoustic and visual stimulus combinations were the same as in the localization task. Participants were instructed to indicate whenever both visual and acoustic information matched in terms of their spatial position. Localization accuracy was not influenced by the visual cue in young adults, but the influence of the visual distractor was strong in old adults, i.e., visual bias was strong. These observations were supported by the unification task where old adults had increased perception of congruent audio–visual directions at all reference positions and even at very large disparities (e.g., ±15°). Conclusively, concurrent information from different sensory systems highly influences auditory localization accuracy in older adults, supporting the notion that multisensory integration is enhanced in older adults.