How a neural network's signaling relates to its structure

How the structure of a neural network gives rise to its dynamics, signaling and function is a fundamental question of both physics and neuroscience. Previously this question had been challenging to address empirically at brain-scale and cellular resolution because no organism had brain-wide cell-resolved measurements of both its nervous system’s wiring and its neural signaling.  To tackle this question, we measured the first brain-wide causal  atlas of neural signaling in the nematode C. elegans using direct optogenetic activation and simultaneous whole-brain calcium imaging (Randi et al., Nature, 2023).  We measured the brain’s neural dynamics in response to systematic activation of nearly every individually resolved neuron in this animal’s brain. We then compared a network description of these signaling interactions to a network description of the brain’s wiring -- the graph of its chemical synapses and gap junctions--- called a connectome.  In recent work published in PRX Life, we explore how the architecture of these two networks descriptions compare (Dvali et al., PRX Life 2025). We find that the most extreme features of the network are preserved in both signaling and anatomical descriptions. For example, the subnetwork of neurons involved in the pharynx form a distinct community in both the wiring and signaling network descriptions. But many other features that are commonly used to characterize networks differ dramatically between the signaling and wiring descriptions of this same brain. We will explore why these two  network descriptions diverge and will discuss implications for inferring the function of larger brains, especially in light of recent rapid progress in the area of connectomics.