Age effects on perceptual restoration of degraded interrupted sentences

Adult cochlear-implant (CI) users show small or non-existent perceptual restoration effects when listening to interrupted speech. Perceptual restoration is believed to be a top-down mechanism that enhances speech perception in adverse listening conditions, and appears to be particularly utilized by older normal-hearing participants. Whether older normal-hearing participants can derive any restoration benefits from degraded speech (as would be presented through a CI speech processor) is the focus of this study. Two groups of normal-hearing participants (younger: age ≤30 yrs; older: age ≥60 yrs) were tested for perceptual restoration effects in the context of interrupted sentences. Speech signal degradations were controlled by manipulating parameters of a noise vocoder and were used to analyze effects of spectral resolution and noise burst spectral content on perceptual restoration. Older normal-hearing participants generally showed larger and more consistent perceptual restoration benefits for vocoded speech than did younger normal-hearing participants, even in the lowest spectral resolution conditions. Reduced restoration in CI users thus may be caused by factors like noise reduction strategies or small dynamic ranges rather than an interaction of aging effects and low spectral resolution.