Evidence has mounted documenting widespread musician enhancements in an evolutionarily ancient subcortical structure, the auditory brainstem, highlighting the brainstem as a structure involved in learning-related brain plasticity (Banai and Kraus, 2007; Krishnan et al., 2009). Musicians not only show more precise subcortical encoding of music, but of speech and emotional communication sounds as well (Kraus and Chandrasekaran, 2010; Kraus et al., 2009). Though remarkable, such observations cannot disambiguate the source of this musician advantage. Does musical training shape subcortical auditory processing, or are individuals born with more refined auditory brainstem function predisposed to pursue musical training? Although neurobiological studies have employed correlational analyses to infer that functional differences between the brains of musicians and nonmusicians are a consequence of the extent of musical practice (Musacchia et al., 2007; Strait et al., 2009; Wong et al., 2007), causality cannot be derived from correlations. Given that experience-related and innate factors likely co-exist, we must clearly define their respective roles in shaping brain function in musicians. Here, we aimed to provide unambiguous evidence for musical training’s impact on auditory brainstem function. The answer to this question bears great significance for sensory learning; if musical training has the power to fine-tune subcortical structures to better process sound, this would attest to the power of cognitive experience to shape basic sensory function.

Until now, subcortical investigations have approached musicians as a homogeneous population (Bidelman et al.,
2009; Musacchia et al., 2007; Parbery-Clark et al., 2009; Strait et al., 2009; Wong et al., 2007). We asked whether or not musical training shapes human brainstem function by examining subgroups of musicians — specifically, musicians trained on different instruments. Guided by the hypothesis that subcortical precision in musicians is driven by extensive musical practice, we expected musicians’ auditory brainstem responses to be uniquely tuned to their instrument of practice relative to other instruments.

Overall, outcomes reveal that musical practice has the power to shape sensory circuitry, newly informing scientific understanding of the biological mechanisms that are fundamental to sensory learning. These mechanisms appear to depend, at least in part, on the corticofugal shaping of basic sensory function in that cognitive functions (here, musical learning) have the power to sculpt human experience of the sensory world.