Corticostriatal interactions give rise to musical expectancy
Building up expectations of listeners and then either fulfilling or violating those expectations is one of the most entertaining aspects of music. For cognitive neuroscientists, this phenomenon presents with a highly interesting research question: how does the brain code musical sequences, such as those in Western classical music, in order to be able to build up harmonic expectations and thus also detect violations of harmonic expectations? Recent neuroimaging research has tentatively suggested that the motor system is involved (instead of only auditory cortical areas) in coding longer musical sequences, but there have been relatively few studies that have attempted to pinpoint the brain structures (as well as interactions between them) that support perception of harmonic expectancies.
In their recent study, Seger et al. (2013) presented 10-24 sec short Western classical melodies to 11 healthy non-musician participants during 3-Tesla functional magnetic resonance imaging. The musical pieces were manipulated so that the degree of expectancy violation varied at four steps from fulfilling of the expectancy to minor, intermediate, and large violations of the harmonic expectancy. The results disclosed multiple brain regions that respond to harmonic violations, including basal ganglia, inferior frontal gyrus, and anterior superior temporal gyrus. Granger causality mapping further revealed connectivity between the basal ganglia, inferior frontal gyrus, anterior and posterior superior temporal gyrus during music perception.
These highly exciting results shed light on the brain structures supporting harmonic expectancy. It appears that basal ganglia and the interactions of basal ganglia with inferior frontal gyrus and anterior superior temporal gyrus support the building up of harmonic expectations and perception of the violation of such expectations. Notably, instead of simplified tonal sequences, the authors utilized unaltered short pieces of music from the works of classical composers (e.g., Bach, Beethoven), thus significantly increasing the ecological validity of their findings.
Reference: Seger CA, Spiering BJ, Sares AG, Quraini SI, Alpeter C, David J, Thaut MH. Corticostriatal contributions to musical expectancy perception. Journal of Cognitive Neuroscience (2013) e-publication ahead of print. http://dx.doi.org/10.1162/jocn_a_00371