Are you surprised to hear this? Longitudinal spectral speech exposure in older compared to middle-aged normal hearing adults

Cognitive abilities such as attention or working memory can support older adults during speech perception. However, cognitive abilities as well as speech perception decline with age, leading to the expenditure of effort during speech processing. This longitudinal study therefore investigated age-related differences in electrophysiological processes during speech discrimination and assessed the extent of enhancement to such cognitive auditory processes through repeated auditory exposure. For that purpose, accuracy and reaction time were compared between 13 older adults (62-76years) and 15 middle-aged (28-52years) controls in an active oddball paradigm which was administered at three consecutive measurement time points at an interval of 2wk, while EEG was recorded. As a standard stimulus, the nonsense syllable /a:?a/was used, while the nonsense syllable /a:sa/ and a morphing between /a:?a/ and /a:sa/ served as deviants. N2b and P3b ERP responses were evaluated as a function of age, deviant, and measurement time point using a data-driven topographical microstate analysis. From middle age to old age, age-related decline in attentive perception (as reflected in the N2b-related microstates) and in memory updating and attentional processes (as reflected in the P3b-related microstates) was found, as indicated by both lower neural responses and later onsets of the respective cortical networks, and in age-related changes in frontal activation during attentional stimulus processing. Importantly, N2b- and P3b-related microstates changed as a function of repeated stimulus exposure in both groups. This research therefore suggests that experience with auditory stimuli can support auditory neurocognitive processes in normal hearing adults into advanced age.