Music and Speech Elicit Similar Subcortical Responses in Human Listeners

Music and speech are two sounds that are unique to human beings and encountered in daily life. Both are transformed by the auditory pathway from an initial acoustical encoding to higher level cognition. Most studies of speech and music processing are focused on the cortex, and the subcortical response to natural, polyphonic music is essentially unstudied. The goal of this study was to compare the subcortical encoding of music and speech using the auditory brainstem response (ABR). While several methods have recently been developed to derive the ABR to continuous speech, they are either not applicable to music or give poor results. In this study, we explored deriving the ABR through deconvolution using three regressors: 1) the half-wave rectified stimulus waveform, 2) the modeled inner hair cell potential, and 3) the auditory nerve model firing rate (ANM), where the latter two were generated from a computational auditory periphery model. After quantitatively comparing the three regressors, we found the ANM regressor yields robust and interpretable ABR waveforms to diverse genres of music and multiple types of speech stimuli. We then used the ANM-derived ABRs to compare the subcortical responses to music and speech and found that they are highly similar in morphology. We further investigated cortical responses using the same deconvolution method, and found the responses there were also quite similar, which was unexpected based on previous studies. Our study first developed approach that can be used to investigate subcortical encoding and processing for both natural speech and music with the potential for use in cortical encoding. Based on that, we concluded that when accounting for acoustical differences’ nonlinear effects on peripheral encoding, the derived music and speech brainstem responses are highly correlated.