A conserved node degree-based backbone and flexible hub organization of brain connectome during naturalistic movie watching.

How does the brain organize and transmit information during naturalistic conditions? Using large-scale movie-watching fMRI data spanning 14 diverse clips, we revealed a degree-based dual architecture of the functional connectome under naturalistic stimuli. During movie watching, the brain consistently expresses a conserved network backbone characterized by persistently high node degree in temporal and occipital sensory cortices and parietal association regions, whereas anterior higher-order regions show relatively lower node degree and substantially greater variability across different clips. We further found that this backbone links brain network organizational patterns to stimulus features of the clips, particularly audiovisual features capturing human presence and social communication. Building on this conserved backbone, different movie clips recruit distinct sets of rich-club hubs, reflecting a flexible hub organization distributed across superior temporal gyrus, temporo-parieto-occipital junction, precuneus/posterior cingulate cortex, intraparietal sulcus, and visual motion-sensitive regions. These hubs serve as key integrative nodes whose connectivity statistically mediates the relationship between stimulus features and cross-network integration. The conserved backbone and rich-club organization were reproduced in an independent movie-watching dataset analyzed with an identical pipeline, providing partial validation of these topological findings. Together, these findings reveal a network-level organizing principle in which a conserved backbone supports stable large-scale coordination, while flexible hub organization enables feature-specific coupling between stimulus features and distributed brain networks.