Temporal Dynamics of Intraparietal Sulcus Activation in Response to Tonal Uncertainty: An fMRI Study of the Diminished Seventh Chord

Tonality and harmony in music provide a structured framework to explore the neural mechanisms underlying uncertainty. The diminished seventh (dim7) chord, characterized by its multiple potential resolutions, serves as an ideal stimulus for examining the neural correlates of tonal uncertainty. This functional magnetic resonance imaging study investigated neural activity elicited by the dim7 chord in listeners with refined music listening skills, focusing on three harmonic progressions: CHANGE, modulating to a distantly related tonality; RETURN, resolving to the original tonality; and PERSIST, sustaining tonal ambiguity through repeated dim7 chords. A finite impulse response model was used to analyze responses in regions associated with uncertainty processing. The intraparietal sulcus (IPS) uniquely exhibited distinct temporal activation patterns across the three conditions. In CHANGE, IPS activity initially decreased, likely reflecting reduced confidence in the outdated tonal model’s predictions, followed by an increase as sensory evidence for a new tonality accumulated. In RETURN, IPS activity showed limited fluctuation. In PERSIST, a progressive increase in IPS activity may reflect heightened cognitive demands for maintaining and evaluating multiple tonalities. These findings deepen our understanding of predictive coding by highlighting the nuanced role of the IPS in processing uncertainty.