Neural correlates of early sound encoding and their relationship to speech in noise perception

Abstract

Speech-in-noise (SIN) perception is a complex cognitive skill that affects social, vocational, and educational activities. Poor SIN ability particularly affects young and elderly populations, yet varies considerably even among healthy young adults with normal hearing. Although SIN skills are known to be influenced by top-down processes that can selectively enhance lower-level sound representations, the complementary role and of feed-forward mechanisms and their relationship to musical training is poorly understood. Using a paradigm that eliminates the main top-down factors that have been implicated in SIN performance, we aimed to better understand how robust encoding of periodicity in the auditory system (as measured by the frequency-following response) contributes to SIN perception. Using magnetoencephalograpy, we found that the strength of encoding at the fundamental frequency in the brainstem, thalamus, and cortex is correlated with SIN accuracy, as was the amplitude of the slower cortical P2 wave, and these enhancements were related to the extent and timing of musicianship. These results are consistent with the hypothesis that basic feed-forward sound encoding affects SIN perception by providing better information to later processing stages, and that modifying this process may be one mechanism through which musical training might enhance the auditory networks that subserve both musical and language functions.Highlights–Enhancements in periodic sound encoding are correlated with speech-in-noise ability–This effect is observed in the absence of contextual cues and task demands–Better encoding is observed throughout the auditory system and is right-lateralized–Stronger encoding is related to stronger subsequent secondary auditory cortex activity–Musicianship is related to both speech-in-noise perception and enhanced MEG signals

Musical training sharpens and bonds ears and tongue to hear speech better

“…Speech encoding with high fidelity in the presence of noise along the auditory pathway is necessary for matching neural representations of incoming acoustic signals to stored lexical representations (9). Previous studies have underscored the importance of faithful encoding of speech (e.g., frequency following response) in brainstem, thalamus, and cortex for speech in noise perception (17). Musicians show superior frequency following responses, including more robust encoding of speech spectral features and greater neural temporal precision (18,31).…”

“…The ability to track and understand speech amid competing sound sources is supported by both the fidelity of bottom-up sensory encoding of target speech (15)(16)(17) and higher-level cognitive processes such as auditory working memory and selective attention (6,18). If musical training improves auditory processing abilities (e.g., pitch, timing, and timbre) and cognitive skills, as well as their interaction, it might free up resources that could then be dedicated to flexibly adapting strategies to specific task demands (2,19).…”

Speech auditory brainstem responses in adult hearing aid users: Effects of aiding and background noise, and prediction of behavioral measures

“…Previous speech-ABR studies have reported relationships between several speech-ABR measures (including F0) and performance on sentences in noise (e.g., Anderson et al, 2011;Anderson, Skoe, Chandrasekaran, Zecker, et al, 2010;Parbery-Clark et al, 2011;Song, Skoe, et al, 2011). Moreover, one neuroimaging MEG study found that stronger F0 representation at different levels of the auditory system was correlated with better performance on behavioral sentences in noise (Coffey, Chepesiuk, et al, 2017). However, these studies tested individuals with normal hearing or older adults with varying hearing levels from normal to mild hearing loss.…”

Brainstem Encoding of Speech and Music Sounds in Humans

“…A consistent finding in FFR literature is that the encoding of the speech f0 is indicative of the ability to hear in noise. In normal hearing listeners of all ages, variability in the aptitude of understanding speech when masked by noise is mirrored in the amplitude of the f0 components in speech (Anderson, Parbery-Clark, Yi, & Kraus, 2011;Anderson, Skoe, Chandrasekaran, Zecker, & Kraus, 2010;Coffey, Chepesiuk, Herholz, Baillet, & Zatorre, 2017;J. Song, Skoe, Banai, & Kraus, 2011).…”