A Neural Basis of Speech-in-Noise Perception in Older Adults

Abstract

Objective We investigated a neural basis of speech-in-noise perception in older adults. Hearing loss, the third most common chronic condition in older adults, is most often manifested by difficulty with understanding speech in background noise. This trouble with understanding speech in noise, which occurs even in individuals who have normal hearing thresholds, may arise, in part, from age-related declines in central auditory processing of the temporal and spectral components of speech. We hypothesized that older adults with poorer speech-in-noise (SIN) perception demonstrate impairments in the subcortical representation of speech. Design In all participants (28 adults, ages 60 to 73 years), average hearing thresholds calculated from 500 to 4000 Hz were ≤ 25 dB HL. The participants were evaluated behaviorally with the Hearing in Noise Test (HINT) and neurophysiologically using speech-evoked auditory brainstem responses recorded in quiet and in background noise. The participants were divided based on their HINT scores into top and bottom performing groups that were matched for audiometric thresholds and IQ. We compared brainstem responses in the two groups, specifically, the average spectral magnitudes of the neural response and the degree to which background noise affected response morphology. Results In the quiet condition, the bottom SIN group had reduced neural representation of the fundamental frequency of the speech stimulus and an overall reduction in response magnitude. In the noise condition, the bottom SIN group demonstrated greater effects of noise, which may reflect reduction in neural synchrony. All physiologic measures correlated with SIN perception. Conclusion Adults in the bottom SIN group differed from the audiometrically-matched top SIN group in how speech was neurally encoded. The strength of subcortical encoding of the fundamental frequency appears to be a factor in successful speech-in-noise perception in older adults. Given the limitations of amplification for improving central auditory processing, our results indicate the need for inclusion of auditory training in intervention plans for older adults with SIN perception difficulties.

A comparison of spectral magnitude and phase-locking value analyses of the frequency-following response to complex tones

“…In contrast to our results, some past studies have demonstrated that additive acoustic noise degrades the FFR ENV response, including at F 0 (e.g., Anderson et al, 2011); however, the size of the effect of additive noise on FFR ENV appears to depend not only on the acoustic properties of the signal and noise, but also on other factors, such as perceptual abilities that can vary across listeners (e.g., see Cunningham et al, 2001;Song et al, 2011). We do not know of any studies of the effects of additive acoustic noise on FFR ENV that used exactly the same stimuli as we employed here (harmonic complexes consisting of the first eight harmonics of 100 Hz, at equal intensity; broadband Gaussian noise).…”

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“…Cognition has emerged as an important concept in the context of speech perception and comprehension in the last fifty years (e.g., Rabbitt, 1968;Rönnberg et al, 2013;Schneider, 2011;van Rooij & Plomp, 1990, 1992Wingfield, Tun, & McCoy, 2005), partly to account for finding that listeners with similar hearing impairments can vary widely in their level of functioning (Anderson, Parbery-Clark, Yi, & Kraus, 2011;GordonSalant & Fitzgibbons, 1993;Vermiglio, Soli, Freed, & Fisher, 2012). Cognition is a multi-faceted concept and in the following section we will limit the discussion of agerelated cognitive changes to those aspects that are most likely to affect spoken-language comprehension.…”

The influence of cochlear spectral processing on the timing and amplitude of the speech-evoked auditory brain stem response

“…Abnormalities in the speech ABR have been repeatedly correlated with deficits in speech-in noise perception, particularly in aging populations (Anderson et al 2011(Anderson et al , 2012Ruggles et al 2012) and in children, usually with language-related learning problems (Anderson et al 2010b;Hornickel et al 2011;Hornickel and Kraus 2013). A peripheral basis for these abnormalities in terms of hearing sensitivity has generally been ruled out, because the participant groups tested presented clinically normal audiograms.…”