The bimusical brain is not two monomusical brains in one: evidence from musical affective processing

Complex auditory exposures in ambient environments include systems of not only linguistic but also musical sounds. Because musical exposure is often passive, consisting of listening rather than performing, examining listeners without formal musical training allows for the investigation of the effects of passive exposure on our nervous system without active use. Additionally, studying listeners who have exposure to more than one musical system allows for an evaluation of how the brain acquires multiple symbolic and communicative systems. In the present fMRI study, listeners who had been exposed to Western-only (monomusicals) and both Indian and Western musical systems (bimusicals) since childhood and did not have significant formal musical training made tension judgments on Western and Indian music. Significant group by music interactions in temporal and limbic regions were found, with effects predominantly driven by between-music differences in temporal regions in the monomusicals and by between-music differences in limbic regions in the bimusicals. Effective connectivity analysis of this network via structural equation modeling (SEM) showed significant path differences across groups and music conditions, most notably a higher degree of connectivity and larger differentiation between the music conditions within the bimusicals. SEM was also used to examine the relationships among the degree of music exposure, affective responses, and activation in various brain regions. Results revealed a more complex behavioral-neural relationship in the bimusicals, suggesting that affective responses in this group are shaped by multiple behavioral and neural factors. These three lines of evidence suggest a clear differentiation of the effects of the exposure of one versus multiple musical systems.