Name:Joshua Hoddinott

School/Affiliation:University of Western Ontario

Co-Authors:Jessica Grahn

Virtual or In-person:In-person

Abstract:

Humans ubiquitously feel an underlying pulse, or ‘beat’, arising from regular musical rhythm. Recently, we’ve shown with fMRI that the supplementary motor area (SMA) and basal ganglia encode beat strength, activating in dissimilar spatial patterns for rhythms of different beat strengths, and activating in similar patterns for rhythms of equal beat strength. Activity patterns in the dorsal (IPL) and ventral (IFG) auditory streams encode different rhythms regardless of beat, with dissimilar activity patterns between rhythms of same and different beat strengths. However, models of beat strength correlated with activity patterns in both IPL and IFG, suggesting some beat-related information represented in these regions. The IPL and IFG may represent the underlying beat and incoming sounds simultaneously via functional connections from SMA and auditory cortex, respectively. Here, we tested whether pattern dissimilarity in the IPL and IFG was best predicted by pattern dissimilarity in primary auditory cortices, beat-sensitive motor regions, or a combination of both. During 7T fMRI, subjects listened to 4 strong-beat, 4 weak-beat, and 4 non-beat rhythms. Dissimilarity between voxel-to-voxel activity patterns was calculated for each pair of rhythms, creating 12x12 representational dissimilarity matrices (RDMs) for the SMA, primary auditory cortex, IPL, and IFG. Using cross-validated multivariate regression, preliminary findings show that RDMs in the IPL and IFG are better predicted by both SMA and auditory cortex RDMs than either alone. The IPL and IFG may be combining bottom-up sensory information with top-down beat-related information, as suggested by the Action Simulation for Auditory Prediction hypothesis (Patel & Iversen, 2014).