Abstract
Older adults exhibit decreased performance and increased trial-to-trial variability on a range of cognitive tasks, including speech perception. We used blood oxygen level dependent functional magnetic resonance imaging (BOLD fMRI) to search for neural correlates of these behavioral phenomena. We compared brain responses to simple speech stimuli (audiovisual syllables) in 24 healthy older adults (53 to 70 years old) and 14 younger adults (23 to 39 years old) using two independent analysis strategies: region-of-interest (ROI) and voxel-wise whole-brain analysis. While mean response amplitudes were moderately greater in younger adults, older adults had much greater within-subject variability. The greatly increased variability in older adults was observed for both individual voxels in the whole-brain analysis and for ROIs in the left superior temporal sulcus, the left auditory cortex, and the left visual cortex. Increased variability in older adults could not be attributed to differences in head movements between the groups. Increased neural variability may be related to the performance declines and increased behavioral variability that occur with aging.
Highlights
The ability of older adults to understand both auditory-only and audiovisual speech declines with age [1,2,3,4]
3.1 Responses in the ROIs to audiovisual speech Our initial analysis focused on three ROIs implicated as critical nodes in the network for multisensory speech perception: the left
Our most robust finding was of greater intrasubject variability in older adults
Summary
The ability of older adults to understand both auditory-only and audiovisual speech declines with age [1,2,3,4]. Older adults exhibit much greater variability in performance: on some trials, older adults perform as well as younger adults, but on other trials, older adults perform much worse [9,10,11] This type of performance decline, referred to as increased intrasubject variability, may be a sensitive measure of age-related changes [12]. Increased neural variability in the auditory brain stem response of healthy older adults has been related to deficits in speech in noise perception [16]. This necessitates continued research to investigate to fully understand the role of response variability in healthy aging
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