Functional ultrasound imaging in free-moving marmosets reveals that intra-call prosodic features modulate large-scale cortical dynamics

Vocal turn-taking relies on sequential structure and rhythmic timing, yet how primate brains integrate these features across timescales in naturalistic, free-moving contexts is unclear. We developed functional ultrasound imaging for free-moving marmosets, combining an exogenous marker-based workflow for robust registration from non-standard imaging planes with preprocessing pipeline optimized to reduce locomotion artifacts. We systematically perturbed sequential and rhythmic features of interactive phee calls across hierarchical timescales. Cortical networks showed selective sensitivity to intra-call structure: disrupting phrase sequences increased activity in auditory and para-insular cortices and strengthened inter-subject functional connectivity within this network. Rhythmic manipulations primarily affected core auditory cortex: shortening inter-phrase intervals enhanced responses, whereas lengthening intervals suppressed them. These findings establish a practical framework for free-moving primate neuroimaging and identify intra-call prosodic features as promising targets for mechanistic investigation.