Extended Data Fig. 9: Network features of the brain map.
From: A multi-scale brain map derived from whole-brain volumetric reconstructions
a, Schematics of network features (from left to right): Feed-forward loop (FF) motif defined by a triplet of nodes with connectivity: Source → Intermediary → Target and Source → Target; network hub (high-degree node); fan-in (high in-degree node); fan-out (high out-degree node); and rich club (highly connected hubs). b, FF triplets within the brain map support the ResNet architecture of the nerve ring. All 101 FF instances among ℂ4 synaptic contacts (all edges in Fig. 4, Extended Data Fig. 10) are shown. Black arrows, synaptic contacts forming FF motifs within the ResNet architecture (Fig. 4); grey arrows, additional synaptic contacts forming FF motifs (Extended Data Fig. 10). A total of 72 out of 93 cell classes participate in at least one FF motif. Prominent FF targets include AIA, AIB, AIZ, AVA, AVB, AVE, RIA, RIC, RIM, RIP, RMDV and SMDV. Additional contacts superimposed on the ResNet come mostly from cross-sensory module connectivity (Extended Data Fig. 10b). c, RIP, the only synaptic link between the somatic and pharyngeal nervous systems, is a major FF target cell for papillary sensory source cells and URA intermediaries. d, AIA is a major taxis layer-2 intermediary cell pair regulating information flow from layer-1 taxis sensory cells onto the layer-3 AIB taxis target cell. e, AIZ, major layer-3 cells that support nonlocal connectivity (Fig. 3a), serve both to integrate information flow from layer-1 and layer-2 taxis source cells (fan-in) and as intermediary connections to various layer-3 target cells in other modules (fan-out). f, Primary locomotion-regulating interneurons—AVA, AVB and AVE—are major layer-3 FF targets and connect extensively onto motor neurons of the ventral nerve cord. Connectivity among these cells occurs in the ventral nerve cord (but is not observed in the nerve ring), suggesting that the regulation of locomotion down the body occurs posteriorly to the nerve ring. g, The cell pair RIM, a major hub that supports nonlocal connectivity, serves a triple purpose as a source, intermediary and target of FF motifs within layer 3. h, The nonlocal supporter, multi-compartment cell pair RIA is a major FF target for layer-1 sensory (primarily avoidance) source cells and for layer-2 and layer-3 (taxis and avoidance) intermediary cells as well as intermediaries that control layer-3 head motor neurons. In addition, RIA neurons are major targets for feedback from lateral (RMD, RMDD, RMDV) and sublateral (SMDD, SMDV) head motor neurons, consistent with their roles in spatially encoding dorso-ventral head movement to coordinate turning behaviours46. i, Major targets of FF motifs (11 neuron classes acting as a target of more than three FF motifs, including five classes of rich club neurons) form a highly interconnected subnetwork. Note the frequent representation of some cells in multiple motifs (c–i). j, Aggregated synaptic contacts of layer-3. Layer-3 FF motifs within and among the modules show strong recurrence and no clear feed-forward directionality or hierarchy of layer-3 connectivity, consistent with highly distributed computation. Sublaterals are merged into the lateral module node. Layer-3 anterior cells form FF motifs with only one other module (taxis). All network schematics were generated with Cytoscape v.3.7.1.
