Effects of Age, Cognition, and Neural Encoding on the Perception of Temporal Speech Cues

Abstract

Older adults commonly report difficulty understanding speech, particularly in adverse listening environments. These communication difficulties may exist in the absence of peripheral hearing loss. Older adults, both with normal hearing and with hearing loss, demonstrate temporal processing deficits that affect speech perception. The purpose of the present study is to investigate aging, cognition, and neural processing factors that may lead to deficits on perceptual tasks that rely on phoneme identification based on a temporal cue – vowel duration. A better understanding of the neural and cognitive impairments underlying temporal processing deficits could lead to more focused aural rehabilitation for improved speech understanding for older adults. This investigation was conducted in younger (YNH) and older normal-hearing (ONH) participants who completed three measures of cognitive functioning known to decline with age: working memory, processing speed, and inhibitory control. To evaluate perceptual and neural processing of auditory temporal contrasts, identification functions for the contrasting word-pair WHEAT and WEED were obtained on a nine-step continuum of vowel duration, and frequency-following responses (FFRs) and cortical auditory-evoked potentials (CAEPs) were recorded to the two endpoints of the continuum. Multiple linear regression analyses were conducted to determine the cognitive, peripheral, and/or central mechanisms that may contribute to perceptual performance. YNH participants demonstrated higher cognitive functioning on all three measures compared to ONH participants. The slope of the identification function was steeper in YNH than in ONH participants, suggesting a clearer distinction between the contrasting words in the YNH participants. FFRs revealed better response waveform morphology and more robust phase-locking in YNH compared to ONH participants. ONH participants also exhibited earlier latencies for CAEP components compared to the YNH participants. Linear regression analyses revealed that cortical processing significantly contributed to the variance in perceptual performance in the WHEAT/WEED identification functions. These results suggest that reduced neural precision contributes to age-related speech perception difficulties that arise from temporal processing deficits.

Neural Generators Underlying Temporal Envelope Processing Show Altered Responses and Hemispheric Asymmetry Across Age

“…Our results concerning the age-related changes in phaselocking are also consistent with event-related potential (ERP) studies, which observed a reduction in phase coherence of auditory brain stem responses to tonal and speech stimuli (Clinard et al, 2010;Anderson et al, 2012;Clinard and Tremblay, 2013;Presacco et al, 2015;Roque et al, 2019). In addition, our results are also consistent with animal studies, where less phaselocking to rapid amplitude modulations has been reported in near-and far-field recordings (Parthasarathy and Bartlett, 2012;Herrmann et al, 2017;Parthasarathy et al, 2019).…”

“…Inhibitory neurotransmission also plays a key role in shaping the response to complex and/or rapid temporally modulated stimuli (Walton et al, 1998;Caspary et al, 2008;Parthasarathy et al, 2010). Reduction in inhibitory neurotransmission in older adults may result in a loss of temporal precision in encoding rapidly changing sounds (Anderson et al, 2012;Roque et al, 2019).…”

“…Many middle-aged and older people experience difficulties following conversations, especially in noisy environments or when multiple speakers are talking simultaneously. While aging is often accompanied by loss of hearing sensitivity in the high frequencies, these difficulties occur even with normal hearing sensitivity most probably due to age-related changes in central temporal processing (e.g., Presacco et al, 2015Presacco et al, , 2019Du et al, 2016;Goossens et al, 2016;Roque et al, 2019). For e.g., Ostroff et al (2003) showed alterations in the central processing of sound duration in older adults as revealed by the amplitude of N1 and P2 waves of auditory evoked potentials.…”

Decoding Hearing-Related Changes in Older Adults’ Spatiotemporal Neural Processing of Speech Using Machine Learning

“…Age-related HI is thought to occur due to a myriad of changes in both the central auditory pathways ( Bidelman et al, 2014 , 2019b ) and widespread areas of both cerebral hemispheres ( Gates and Mills, 2005 ). For example, studies have shown aged-related declines in the temporal precision ( Roque et al, 2019 ) of (subcortical) neural encoding ( Anderson et al, 2012 ; Konrad-Martin et al, 2012 ; Bidelman et al, 2014 ; Schoof and Rosen, 2016 ) and functional magnetic resonance imaging (fMRI) has shown older adults have greater activation than younger adults in widespread cortical brain regions ( Du et al, 2016 ; Mudar and Husain, 2016 ; Diaz et al, 2018 ). Older adults with hearing impairment show even greater activation in right hemisphere (RH) than the left hemisphere (LH) during speech perception in noise ( Mudar and Husain, 2016 ).…”

Defining the Role of Attention in Hierarchical Auditory Processing

“…While some of these abilities are altered due to age, hearing loss, or auditory processing disorders, other cognitive factors attempt to compensate for associated declines in these areas [ 25 , 29 ]. For instance, age results in reduced processing speed which contributes to poorer temporal processing abilities and ultimately impaired speech perception [ 25 , 31 ]. When linguistic context is added to temporally degraded speech, older adults capitalize on prior linguistic knowledge to improve performance and overcome some of the challenges introduced by typical aging [ 25 ].…”