The Experiment: Eavesdropping on 37 Mushrooms in a Night Forest
On October 23, 2022, at 11:45 PM, Yu Fukasawa's team walked into a secondary mixed forest dominated by *Quercus serrata* in Kami, Miyagi, Japan, carrying a GRAPHTEC GL840-Midi industrial voltage logger. Six months earlier, they had applied urea to a 5 m × 5 m plot at an extreme dose (640 g/m²)—not as fertilizer, but as bait. Urea breaks down into ammonia, which awakens "ammonia fungi" that rarely fruit under normal conditions.
That night, 37 mushrooms had emerged: 29 *Hebeloma danicum* and 8 *Hebeloma cylindrosporum*, belonging to different genetic clones (genets) and different mycelial networks. The team inserted 37 pairs of stainless-steel subcutaneous needle electrodes—one in each cap, one at each stem base—measuring potential differences at one reading per second (±100 mV range) for 3.5 days.
During recording, they applied targeted stimuli: 200 ml of tap water at a single mushroom's base, 200 ml of human urine (from one of the authors, a healthy 44-year-old male), and finally a uniform spray of 10 L/m² of water across the entire plot, simulating heavy rain.
Results were published March 2, 2026, in *Scientific Reports*: *Electrical information flows across the sporocarps of two ectomycorrhizal fungi in the field* (DOI: 10.1038/s41598-026-42673-y).
Background: How Fungi "Speak" Electrically
Fungi have no nervous system and no centralized information processing. But mycelium—tubular cells with ionic gradients across membranes—generates electrical potential changes that propagate along hyphae. Unlike neuronal action potentials (digital, all-or-nothing), fungal electrical signals are analog, varying continuously from a few to tens of millivolts.
In 2022, Andrew Adamatzky (University of the West of England) recorded 24 hours of electrical activity from four fungal species—including enoki (*Flammulina velutipes*) and ghost fungus (*Omphalotus nidiformis*)—and found spike clusters resembling "words" in linguistic analysis. Fungal "vocabularies" ranged from 14 to 50, with fewer than 15–20 high-frequency terms, and inter-word interval distributions showed statistical similarity to human language. Published in *Royal Society Open Science* (DOI: 10.1098/rsos.211926), the study was cautiously framed: the signals are structured, not noise—and structure implies information.
Key Findings from the 37-Mushroom Network
Using Granger causality—if past values of time series A improve predictions of time series B beyond B's own past—Fukasawa's team built a 37×37 information-flow matrix. Three findings stand out:
- Information flow crosses clone and species boundaries. Signals were not confined to a single mycelial network. The likely channel is the soil itself: one mushroom's hyphal activity alters local soil ion concentrations, which neighboring fungi detect—a "chemical telegraph."
- Information flow decays with both genetic and spatial distance. Cross-species flow was weaker than same-species; cross-clone weaker than same-clone. This dual decay pattern is evidence of genuine signal transmission with loss, not synchronized response to shared environmental factors.
- Local water increased information flow; global water reduced it. Pouring 200 ml of water at one mushroom's base significantly increased average network information flow. Spraying the whole plot uniformly dramatically reduced it.
"When Everyone Already Knows, No Need to Say It"
Fukasawa's own explanation is the study's most striking insight:
> "Applying water to all the mushrooms may mean that there's no need to share information since the whole network already knows what's going on, which could be why the flow of information decreased in this situation."
This maps directly onto an information theory principle: information equals the reduction of uncertainty. When one mushroom receives local water, its neighbors don't yet know—the news is worth transmitting. When the entire plot is watered, every node holds the same information; redundancy hits 100% and communication drops to minimum.
The urine experiment reinforces this. These ammonia fungi were already in a nitrogen-rich state induced by urea six months earlier. Urine—a nitrogen signal—is "old news" to them; it produced the smallest change in information flow. Water, an unexpected stimulus, is "news" and gets propagated. This contrast between news and old news distinguishes genuine communication from mere physical signal conduction.
Implications: A Distributed Information Network with No Designer
The "Wood Wide Web" concept has long faced a skeptical question: is mycelial resource exchange communication, or passive physical diffusion? This study offers a rebuttal—fungal electrical signals are actively generated, structured, and modulated by information redundancy, following information-theoretic rather than purely biochemical rules.
The mycelial network is not just a resource pipeline but an information network exhibiting redundancy elimination, distance decay, and cross-node propagation—all without a brain, a center, or a designer. It is a self-organizing system refined over roughly 400 million years of plant-fungal mycorrhizal symbiosis.
There is also a mirror here for human systems. In federated learning, distributed training (AllReduce instead of full connectivity), and multi-agent communication protocols, we have reinvented redundancy elimination. But our own networks lack a mechanism to detect "does the other party already know this?"—we forward news everyone has seen and repeat statements everyone has heard. The fungal network learned to fall silent when information redundancy is high. That silence is not a failure; it is efficiency at its extreme.
References
1. Fukasawa, Y., Akai, D., Takehi, T., Takahashi, D., & Osada, Y. (2026). Electrical information flows across the sporocarps of two ectomycorrhizal fungi in the field. *Scientific Reports*. DOI: 10.1038/s41598-026-42673-y 2. Adamatzky, A. (2022). Language of fungi derived from their electrical spiking activity. *Royal Society Open Science*, 9(4), 211926. DOI: 10.1098/rsos.211926 3. Fukasawa, Y., et al. (2023). Mushroom's electrical conversation after the rain. *SSRN Electronic Journal*.