Extended Data Fig. 9: Hallucinogenic 5-HT_2A receptor agonism alters inter- vs. intra-network connectivity.

a) Whole-cortex RSFC matrices. Average, pre-injection, whole-cortex RSFC matrices across mice (\(n=8\)) for infralow (ISA; 0.02-0.08Hz) calcium and HbT activity and delta (0.5-4Hz) calcium activity. Matrices represent all pixel-pair comparisons and are organized by network assignment. b) Hierarchical clustering of RSFC. RSFC matrices were hierarchically clustered using Ward’s method and visualized as a dendrogram. c) Resultant clusters at a specific hierarchical level. A distance threshold was selected to create a parcellation containing 13 clusters. These parcels were used to assess inter- and intra-regional relationships. d) Pre-injection Silhouette scores. Silhouette scores were computed at each pixel to assess the ratio between cohesion (intra-cluster distance metric) and separation (inter-cluster metric). Silhouette scores range from -1 to +1, such that +1 indicates a point is well-clustered and far from neighboring clusters (strongly intra-connected, weakly inter-connected), 0 indicates that the point is on, or near, the boundary between two clusters (equally intra- and inter-connected/equally likely to belong to any neighboring cluster), and -1 indicates a point is misclassified and likely should be assigned to a different cluster than its own (weakly intra-connected, strongly inter-connected). i) A graphical demonstration of cohesion (black cluster) and separation to the nearest cluster (red cluster). ii) Pre-injection silhouette scores for each species and frequency band. e) Changes in Silhouette scores after compound injection. DOI (4mg/kg) predominantly decreases ISA calcium silhouette scores everywhere (regions are less intra-connected and more inter-connected), an effect not fully reversed in under DOI+MDL. Importantly, ISA calcium scores in the cingulate and retrosplenial cortices—constellations of the mouse default mode network—showed opposite effects: cingulate scores marginally increased, while retrosplenial scores markedly decreased. This divergence was substantially reduced when scores were computed using infralow hemodynamic activity. Delta calcium activity under DOI suggests that the compound primarily alters network boundaries rather than modulating inter- or intra-network interactions.