Auditory-Visual Integration in Younger and Older Adults

This study examined age-related changes in the ability to integrate auditory and visual speech information. Visual enhancement, the advantage afforded by seeing as well as hearing a talker, compared with listening alone, was measured in younger (18-25) and older (over age 65) adults. In addition, dichotic identification of filtered speech (auditory-auditory speech integration) and binaural gap detection (auditory-auditory non-speech integration) were tested to evaluate whether auditory-visual integration was related to a more global ability to integrate sensory signals, be they speech or nonspeech. Visual enhancement was significantly impaired in older, compared with younger adults. Most importantly, visual-only (lipreading) performance of younger and older adults was nearly identical, suggesting that age-related declines in visual enhancement were not a result of reduced reception of visual information. Older adults also exhibited deficits in the ability to integrate two channels of auditory information and these deficits were similar for both speech (sentences) and nonspeech (gap detection) stimuli. Regression analyses indicated significant correlations between the three measures of sensory integration, visual enhancement, dichotic sentence identification, and binaural gap detection. Taken together, the findings suggest that age-related declines in visual enhancement are a result of a generalized decline in sensory integration abilities.