The dynamic emergence of musical pitch structure in human cortex

Abstract

Tonal music the world over is characterized by a hierarchical structuring of pitch, whereby certain tones appear stable and others unstable within their musical context. Despite its prevalence, the cortical mechanisms supporting such a percept remain poorly understood. The current study probed the neural processing dynamics underlying the representation of pitch in Western Tonal Music. Listeners were presented with tones comprising all twelve pitch-classes embedded within a musical context whilst having their magnetoencephalographic (MEG) activity recorded. Using multivariate pattern analysis (MVPA), decoders attempted to classify the identity of tones from their corresponding MEG activity at each peristimulus time sample, providing a dynamic measure of their cortical dissimilarity. Time-evolving dissimilarities between tones were then compared with the predictions of several acoustic and perceptual models. Following tone onset, we observed a temporal evolution in the brains representation. Dissimilarities between tones initially reflected their fundamental frequency separation, but beyond 200 ms reflected their status within the tonal hierarchy of perceived stability. Furthermore, when the dissimilarities corresponding to this latter period were transposed into different keys, cortical relations between keys correlated with the well-known circle of fifths. Convergent with fundamental principles of music-theory and perception, current results detail the dynamics with which the complex perceptual structure of Western tonal music emerges in human cortex within the timescale of an individual tone.\n\nSignificance statementIn music, pitch is organized along a hierarchy of perceived stability. Applying stimulus decoding techniques to the Magnetoencephalographic activity of subjects during music-listening, we examined the structure of this hierarchy in cortex and the dynamics with which it emerges at the timescale of an individual tone. Following its onset, we observed a temporal evolution in the brains representation of a tone. Activity initially reflected its pitch-value (fundamental frequency) before reflecting its status within the tonal hierarchy of perceived stability. Transposing this later period of activity into different musical keys, we found that inter-key distances reflected the well-known circle of fifths. Our results provide a link between the complex perceptual structure of tonal music and its dynamic emergence in cortex.