Effects of age and spectral shaping on perception and neural representation of stop consonant stimuli

Abstract

Objective To determine if (1) aging affects neural representation of a dynamic spectral speech cue and (2) spectrally-shaped gain applied to the cue reduces any aging effects. Methods Psychometric functions and cortical evoked responses were compared in young and older listeners with normal hearing. Stimuli were consonant-vowels along a /bdg/ place-of-articulation continuum in an unshaped and shaped condition. Shaped stimuli enhanced audibility of the F2 formant transition relative to the rest of the stimulus. Results Compared with younger listeners, older listeners had larger /d/ categories, longer P2 latencies, and larger N1 amplitudes to unshaped stimuli. To shaped stimuli, older listeners had /d/ categories and P2 latencies more similar to those measured from younger listeners, while N1 amplitudes were larger. Conclusions Aging significantly affects the processing of dynamic spectral information. For some measures, differences due to aging were minimized with spectrally-shaped stimuli. Significance Aging reduces neural responsiveness to dynamic spectral cues. If the cue is enhanced, neural responsiveness is increased and perceptual measures are more like those from the younger listeners for some stimuli. This suggests that aging may decrease responsiveness of intact neurons as opposed to destroying neurons and/or distorting spectral coding.