EFFECTS OF AGING ON VOICE-PITCH PROCESSING: THE ROLE OF SPECTRAL AND TEMPORAL CUES
Schvartz, Kara Chantal
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Declines in auditory temporal processing are a common consequence of natural aging. Interactions between aging and spectro-temporal pitch processing have yet to be thoroughly investigated in humans, though recent neurophysiologic and electrophysiologic data lend support to the notion that periodicity coding using only unresolved harmonics (i.e., those available via the temporal envelope) is negatively affected as a consequence of age. Individuals with cochlear implants (CIs) must rely on the temporal envelope of speech to glean information about voice pitch [coded through the fundamental frequency (f0)], as spectral f0 cues are not available. While cochlear implants have been shown to be efficacious in older adults, it is hypothesized that they would experience difficulty perceiving spectrally-degraded voice-pitch information. The current experiments were aimed at quantifying the ability of younger and older listeners to utilize spectro-temporal cues to obtain voice pitch information when performing simple and complex auditory tasks. Experiment 1 measured the ability of younger and older NH listeners to perceive a difference in the frequency of amplitude modulated broad-band noise, thereby exploiting only temporal envelope cues to perform the task. Experiment 2 measured age-related differences in f0 difference limens as the degree of spectral degradation was manipulated to approximate CI processing. Results from Experiments 1 and 2 demonstrated that spectro-temporal processing of f0 information in non-speech stimuli is affected in older adults. Experiment 3 showed that age-related performances observed in Experiments 1 and 2 translated to voice gender identification using a natural speech stimulus. Experiment 4 attempted to estimate how younger and older NH listeners are able to utilize differences in voice pitch information in everyday listening environments (i.e., speech in noise) and how such abilities are affected by spectral degradation. Comprehensive results provide further insight on pitch coding in both normal and impaired auditory systems, and demonstrate that spectro-temporal pitch processing is dependent upon the age of the listener. Results could have important implications for elderly cochlear implant recipients.