2 FALLON ET AL. motifs. Our findings demonstrate a conserved property of mouse and human brain organization, in which a brain region's spontaneous activity fluctuations are closely related to their surrounding structural scaffold. K E Y W O R D S structure-function relationship, time-series analysis, structural connectivity, resting-state fMRI, interspecies comparison 1 | INTRODUCTION The brain's complex spatiotemporal dynamics unfold on an intricate web of axonal connections: the connectome [1, 2]. These pathways facilitate information transfer between brain regions, manifesting in a complex relationship between connectome structure and neural dynamics. Reflecting the pairwise nature of structural connectivity (regionregion), existing studies have overwhelmingly compared pairwise measurements of anatomical connectivity to pairwise statistical relationships between neural activity time series, or functional connectivity, often using simulations of network dynamics to better understand how the observed relationships may arise [3-18]. Structural connectivity is highly informative of functional connectivity, consistent with the connectome as a physical substrate constraining inter-regional communication dynamics.Our understanding of pairwise structure-function relationships in the brain remains disconnected from our understanding of how a brain area's structural connectivity properties shape its activity dynamics. Indeed, the structural connectivity profile of a region's incoming and outgoing axonal connections is thought to define its function [19]. Furthermore, the activity dynamics of brain areas follow a functional hierarchy, with rapid dynamics in 'lower' sensory regions, and slower fluctuations in 'higher' regions associated with integrative processes [20][21][22][23][24]. The spatial variation of intrinsic timescales has been measured using ECOG [21], MEG [25,26], TMS-EEG [27], and fMRI [24,[28][29][30][31][32][33], and may a function variation in temporal receptive windows: timescales over which new information can be actively integrated with recently received information [20,33,34]. Spatial variation in intrinsic activity fluctuations may form a key basis for the brain's functional hierarchical organization, shaped by structural variation in the brain's microcircuitry [35][36][37]. This organization is thought to be important for behavior and cognition [20,[38][39][40], and its disruption has clinical implications: e.g., differences in intrinsic timescales are associated with symptom severity in autism [33]. While much is known about the structure-function relationship at the level of brain-region pairs, and how structural and functional connectivity architecture shape cognitive function and are affected in disease [41][42][43][44], relatively little is known about how it affects the information processing dynamics of individual brain areas. In particular, we do not yet understand the role structural connections play in the cortical organization of intrinsic timescales.Recent work has provided statistical e...