Biological impact of auditory expertise across the life span: musicians as a model of auditory learning

Abstract

Experience-dependent characteristics of auditory function, especially with regard to speech-evoked auditory neurophysiology, have garnered increasing attention in recent years. This interest stems from both pragmatic and theoretical concerns as it bears implications for the prevention and remediation of language-based learning impairment in addition to providing insight into mechanisms engendering experience-dependent changes in human sensory function. Musicians provide an attractive model for studying the experience-dependency of auditory processing in humans due to their distinctive neural enhancements compared to nonmusicians. We have only recently begun to address whether these enhancements are observable early in life, during the initial years of music training when the auditory system is under rapid development, as well as later in life, after the onset of the aging process. Here we review neural enhancements in musically trained individuals across the life span in the context of cellular mechanisms that underlie learning, identified in animal models. Musicians' subcortical physiologic enhancements are interpreted according to a cognitive framework for auditory learning, providing a model in which to study mechanisms of experience-dependent changes in human auditory function.

Figure 1. Musicians’ neural enhancements to speech build up over the life span

Average auditory brainstem responses to the speech sound /da/ in musicians and nonmusicians in each of four age groups. Responses were recorded using three scalp-electrodes (A) in quiet and noise and are presented in both temporal and spectral domains (B). **p<0.01 Adapted from Parbery-Clark, et al., 2012; Parbery-Clark, Skoe, Lam, et al., 2009; Strait, Parbery-Clark, et al., 2012; and Strait, et al., in press.

Figure 2. Musicians across the life span have faster neural responses than nonmusicians to the formant transition of the speech syllable /da/

Bar graphs depict average latencies for the first consistent peak in the response to the formant transition region of /da/ in quiet and noise conditions (occurring at ~43 ms post-stimulus onset). Error bars depict one standard error. Adapted from Parbery-Clark, et al., 2012; Parbery-Clark, Skoe, Lam, et al., 2009; Strait, Parbery-Clark, et al., 2012; and Strait, et al., in press. *p<0.05, **p<0.01, ***p<0.001

Figure 3. Musicians have more distinct neural responses to contrasting speech sounds than nonmusicians across the life span

Cross-phaseograms indicate phase differences between responses to /ga/ and /ba/ as a function of frequency over time. Phase shift in radians is indicated by color, with warm colors indicating phase-lead and cool colors indicating phase-lag. Musicians have greater phase shifts than nonmusicians in response to the formant transition, indicating a phase-lead in the response to /ga/. The acoustics of the sustained vowel are identical between stimuli and responses show an appropriate lack of phase shift. Adapted from Strait, et al, 2013.

Figure 4. Auditory abilities and neural responses to speech relate to extent of music training in young adults and children

~p<0.1, *p<0.05, **p<0.01, ***p<0.001