The frontotemporal organization of the arcuate fasciculus and its relationship with speech perception in young and older amateur singers and non‐singers

Abstract

The ability to perceive speech in noise (SPiN) declines with age. Although the etiology of SPiN decline is not well understood, accumulating evidence suggests a role for the dorsal speech stream. While age‐related decline within the dorsal speech stream would negatively affect SPiN performance, experience‐induced neuroplastic changes within the dorsal speech stream could positively affect SPiN performance. Here, we investigated the relationship between SPiN performance and the structure of the arcuate fasciculus (AF), which forms the white matter scaffolding of the dorsal speech stream, in aging singers and non‐singers. Forty‐three non‐singers and 41 singers aged 20 to 87 years old completed a hearing evaluation and a magnetic resonance imaging session that included High Angular Resolution Diffusion Imaging. The groups were matched for sex, age, education, handedness, cognitive level, and musical instrument experience. A subgroup of participants completed syllable discrimination in the noise task. The AF was divided into 10 segments to explore potential local specializations for SPiN. The results show that, in carefully matched groups of singers and non‐singers (a) myelin and/or axonal membrane deterioration within the bilateral frontotemporal AF segments are associated with SPiN difficulties in aging singers and non‐singers; (b) the structure of the AF is different in singers and non‐singers; (c) these differences are not associated with a benefit on SPiN performance for singers. This study clarifies the etiology of SPiN difficulties by supporting the hypothesis for the role of aging of the dorsal speech stream.

Amateur singing benefits speech perception in aging under certain conditions of practice: behavioural and neurobiological mechanisms

“…While it is possible that amateur singing does not in uence SPiN to the same extent as musical instrument playing, it is also possible that the effect of musical activities on SPiN follows a dosedependent relationship, with more intense or more frequent practice being associated with increased bene ts. This is consistent with the ndings that, compared to non-musicians, both amateur singers and professional instrumentalists exhibit differences in the function or structure of the dorsal speech stream, but that these differences were associated to a SPiN advantage only in professionals, not in amateurs (Du and Zatorre 2017;Perron et al 2021). The notion of a dose-dependent effect of musical practice on SPiN is also consistent with the literature on music-induced plasticity, which shows that differences in brain anatomy between instrumentists and non-musicians are related to several practice-related behaviours, such that increased plasticity is related to lower age of onset of musical practice, a higher number of years of practice, a higher number of weekly hours of practice, etc.…”

“…This notion is in line with the Overlap, Precision, Emotion, Repetition, Attention (OPERA) hypothesis (Patel 2014(Patel , 2012(Patel , 2011, which suggests that musical activities affect speech skills by driving plasticity within speech networks when musical practice is frequent. In our previous study (Perron et al 2021), although we found that the number of years of continuous singing was associated to a small extent with the structure of the arcuate fasciculus, we did not identify a relationship between the number of years of continuous singing and SPiN. However, several other singing practice behaviours, such as frequency of singing, duration of choral practice, age at onset of singing, etc., could drive plasticity within auditory and dorsal speech stream regions and, in turn, lead to better SPiN performance.…”

“…Consistent with this idea, a recent study has shown that a SPiN advantage for young professional musicians compared to young non-musician was associated with slightly increased activity in right auditory associative and frontal motor cortices (Du and Zatorre 2017), supporting the notion that musical activities may in uence SPiN through their effect on auditory and dorsal speech stream regions. Relatedly, a recent study from our group found anatomical differences in the structure of the bilateral arcuate fasciculus -which forms the framework for dorsal speech stream-between young and older adult non-singers and adult amateur choral singers (Perron et al 2021). However, these differences were not associated with a bene cial effect of singing on SPiN performance.…”

Amateur Singing Benefits Speech Perception in Aging Under Certain Conditions of Practice: Behavioural and Neurobiological Mechanisms.

“…All participants provided informed consent and received a small monetary compensation for their participation. Behavioural and diffusion MRI collected as part of this project have been published elsewhere (Perron et al 2021). e Health = self-reported general health status on a scale of 0 to 7, with 0 being the lowest health level and 7 the maximal one.…”

“…A negative value of c indicates a bias toward responding "identical" whereas a positive value of c represents a bias towards responding "different". A value of zero indicates the absence of bias.Since we previously reported no difference in SPiN performance between the singers and the non-singers in the two noise conditions for sensitivity (d')(Perron et al 2021), here we averaged the two conditions of noise for each metric (mean accuracy, d', c, RT). For each dependent variable (mean accuracy, d', c, RT), normality was assessed via visual inspection of histograms and Q-Q plots and the homogeneity of variance was assessed using Levene's test (p ≥ .05).…”