Neurophysiological improvements in speech-in-noise task after short-term choir training in older adults.

www.aging-us.com AGING 2021, Vol. 13, No. 7 Research Paper Neurophysiological improvements in speech-in-noise task after shortterm choir training in older adults Sarah Hennessy1, Alison Wood1, Rand Wilcox2, Assal Habibi1 1 Brain and Creativity Institute, University of Southern California, Los Angeles, CA 90089, USA Department of Psychology, University of Southern California, Los Angeles, CA 90089, USA 2 Correspondence to: Assal Habibi; email: Keywords: auditory perception, aging, music, speech-in-noise, electroencephalography Received: December 22, 2020 Accepted: March 26, 2021 Published: April 6, 2021 Copyright: © 2021 Hennessy et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ABSTRACT Perceiving speech in noise (SIN) is important for health and well-being and decreases with age. Musicians show improved speech-in-noise abilities and reduced age-related auditory decline, yet it is unclear whether short term music engagement has similar effects. In this randomized control trial we used a pre-post design to investigate whether a 12-week music intervention in adults aged 50-65 without prior music training and with subjective hearing loss improves well-being, speech-in-noise abilities, and auditory encoding and voluntary attention as indexed by auditory evoked potentials (AEPs) in a syllable-in-noise task, and later AEPs in an oddball task. Age and gender-matched adults were randomized to a choir or control group. Choir participants sang in a 2-hr ensemble with 1-hr home vocal training weekly; controls listened to a 3-hr playlist weekly, attended concerts, and socialized online with fellow participants. From pre- to post-intervention, no differences between groups were observed on quantitative measures of well-being or behavioral speech-in-noise abilities. In the choir group, but not the control group, changes in the N1 component were observed for the syllable-in-noise task, with increased N1 amplitude in the passive condition and decreased N1 latency in the active condition. During the oddball task, larger N1 amplitudes to the frequent standard stimuli were also observed in the choir but not control group from pre to post intervention. Findings have implications for the potential role of music training to improve sound encoding in individuals who are in the vulnerable age range and at risk of auditory decline. INTRODUCTION In the United States, 25% of adults over aged 64-74, and 50% of adults over the age of 75 experience hearing loss [1]. Auditory difficulties can be due to sensorineural hearing loss, conductive hearing loss, or central hearing loss, which encompasses deterioration or damage to ascending auditory pathways beyond the cochlea [2]. One consequence of central hearing loss is the reduction in ability to understand speech in noisy environments. Speech-in-noise (SIN) discrimination is notably difficult to target with hearing aids [3, 4], and deficits may exist even in the presence of a clinically normal audiogram [5]. Communication difficulties that result from hearing www.aging-us.com 9468 loss produce strain on social relationships and quality of life. Specifically, auditory decline is associated with loneliness [6], depression [7, 8], substance abuse [9], and reduced social functioning [7, 10, 11]. To address the dramatic impact of speech-in-noise discrimination loss on quality of life, it is relevant to both investigate ways to prevent decline and to improve speech-in-noise abilities in older adults. Music training is a reasonable candidate to improve auditory abilities by fine-tuning perceptual abilities of sound and enhancing discrimination between streams of sound in a complex auditory scene. Accordingly, adult musicians show enhanced performance on sentence-in-noise [12–15], masked sentence [16–19], word-in-noise [20], and gap-in-noise AGING [21] tasks as compared to non-musicians. Additionally, Ruggles et al., [22] observed a significant correlation in speech-in-noise abilities with years of music training in adults. In older adults, musicians additionally outperform non-musicians in sentence-in-noise [23, 24] and word-in-noise discrimination [23, 25]. Fostick, 2019 demonstrated that the musician advantage for words-in-noise discrimination remained when comparing older adult musicians to life-long card players. Zendel and Alain [26] found that the rate of speech-in-noise decline associated with age was less steep in musicians as compared to non-musicians, indicating that music training may protect against agerelated hearing difficulties. Speech-in-noise difficulties are thought to reflect reduced synchrony of neuronal firing [27–29], and are associated with alterations to both bottom-up and topdown processing [30]. Perceiving speech in noise relies on encoding acoustic features, such as frequency or temporal structure, through bottom-up processes in combination with recruiting attentional resources, memory, and contextual prediction through top-down processes. In age-related hearing decline, individuals may compensate for bottom-up sensory deficits with greater reliance on top-down mechanisms, filling in missed pieces of information [31]. In situations of cognitive decline, these compensatory resources may be less available, resulting in further reduced speech-innoise perception [32, 33]. Thus, both top-down and bottom-up mechanisms are important for supporting speech-in-noise perception in older adults and can be dissociated and assessed at the level of the brain. Specifically, neural responses to speech-in-noise can be measured with event-related potentials, voltage recorded from scalp electrodes evoked by a stimulus [34]. Specifically, the P1, N1, P2, and P3 components are utilized to assess auditory processing, including SIN, at a cortical level. The P1 potential (sometimes referred to as P50) peaks around 70-100ms poststimulus onset, is the first cortical component of the auditory response [35, 36] and has a fronto-central distribution. It is thought to originate in the primary auditory cortex and the reticular activating system [36, 37], and becomes more robust with age [38]. N1 is a negative deflection peaking around 100ms after stimulus onset and is most reliably has a frontal and fronto-central distributions on the scalp [39]. N1 is thought to originate in the primary auditory cortex, specifically from the posterior supratemporal plane, Heschl’s gyrus, and the planum temporal [37, 40, 41], and may be modulated by prefrontal regions engaged in attention processes [42]. A vertically-oriented or “tangential” dipole in the primary auditory cortex, in parallel with orientation of auditory cortex neurons, is likely responsible for generating the negative potential www.aging-us.com 9469 recorded in frontal and frontocentral sites [ (...truncated)