ERP evidence that auditory-visual speech facilitates working memory in younger and older adults

Auditory-visual (AV) speech enhances speech perception and facilitates auditory processing, as measured by event-related brain potentials (ERPs). Considering a perspective of shared resources between perceptual and cognitive processes, facilitated speech perception may render more resources available for higher-order functions. This study examined whether AV speech facilitation leads to better working memory (WM) performance in 23 younger and 20 older adults. Participants completed an n-back task (0- to 3-back) under visual-only (V-only), auditory-only (A-only), and AV conditions. The results showed faster responses across all memory loads and improved accuracy in the most demanding conditions (2- and 3-back) during AV compared with unisensory conditions. Older adults benefited from the AV presentation to the same extent as younger adults. WM performance of older adults during the AV presentation did not differ from that of younger adults in the A-only condition, suggesting that an AV presentation can help to counteract some of the age-related WM decline. The ERPs showed a decrease in the auditory N1 amplitude during the AV compared with A-only presentation in older adults, suggesting that the facilitation of perceptual processing becomes especially beneficial with aging. Additionally, the N1 occurred earlier in the AV than in the A-only condition for both age groups. These AV-induced modulations of auditory processing correlated with improvement in certain behavioral and ERP measures of WM. These results support an integrated model between perception and cognition, and suggest that processing speech under AV conditions enhances WM performance of both younger and older adults.