Hierarchical modular structure of the C. elegans signal propagation and anatomical networks. Credit: PRX Life (2025). DOI: 10.1103/6wgv-b9m6
How a brain’s anatomical structure relates to its function is one of the most important questions in neuroscience. It explores how physical components, such as neurons and their connections, give rise to complex behaviors and thoughts. A recent study of the brain of the tiny worm C. elegans provides a surprising answer: Structure alone doesn’t explain how the brain works.
C. elegans is often used in neuroscience research because, unlike the incredibly complex human brain, which has billions of connections, the worm has a very simple nervous system with only 302 neurons. A complete, detailed map of every single one of its connections, or brain wiring diagram (connectome), was mapped several years ago, making it ideal for study.
In this research, scientists compared the worm’s physical wiring in the brain to its signaling network, how the signals travel from one neuron to another. First, they used an electron microscope to get a detailed map of the physical connections between its nerve cells. Then, they activated individual neurons with light to create a signaling network and used a technique called calcium imaging to observe which other neurons responded to this stimulation. Finally, they used computer programs to compare the physical wiring map and the signal flow map, identifying any differences and areas of overlap.
The team discovered that the brain’s functional organization differs from its anatomical structure. An analogy is that the brain’s structure is like a city map showing every street. However, the function is more akin to traffic flow, with jams, detours and shortcuts that are not visible on the map. In other words, brain activity does not always follow the predictable pathways of its physical wiring.
“Our results provide new insight into the interplay between brain structure, in the form of a complete synaptic-level connectome, and brain function, in the form of a system-wide causal signal propagation atlas,” wrote the researchers in their paper published in PRX Life. “Collectively, our findings suggest that the effective signaling network…has different network properties from the underlying connectome.”
While the physical and signal maps differed significantly, a few features were preserved. For example, the physical and signal wiring maps of the worm’s feeding organ (pharynx) look the same.
What it means for us
The research may well have been conducted in a tiny worm, but the findings have enormous implications for us. They suggest that scientists need to look beyond the brain’s wiring to fully understand how it works. This may help improve our understanding of neurological disorders like Alzheimer’s and schizophrenia, which involve an interruption in the brain’s ability to process information.
Written for you by our author Paul Arnold, edited by Lisa Lock, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive.
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More information:
Sophie Dvali et al, Diverging Network Architecture of the C. elegans Connectome and Signaling Network, PRX Life (2025). DOI: 10.1103/6wgv-b9m6
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A new look at how the brain works reveals that wiring isn’t everything (2025, September 24)
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