A hundred years ago, Edgar Adrian recorded from a single nerve fibre and showed the stimulus out in the world is carried in the rate of its firing — he started calling the impulses a "code." We've been trying to read that code ever since. For parts of the brain like V1 we've had a good answer for more than fifty years, and it was written in math: a Gabor filter. Orientation, spatial frequency, phase — compact, and you could measure how well it fit. Deeper in the hierarchy, in areas like V4, we never had the equivalent. We mostly had qualitative descriptions — they fire to shape, color and texture — but couldn't write down a more precise one for a single neuron, let alone put a number on how well it captured what the neuron responds to. Our new paper from The Enigma Project, led by @vedanglad, uses vision-language models to write that correspondence in ordinary human words. The words don't just give a qualitative description of what each neuron is tuned for; crucially, they let you quantify how well that language captures the tuning. Take a neuron's description, regenerate fresh images from it with a diffusion model, show them to a digital twin, and measure: descriptions written to drive V4 neurons pushed 96.1% of them into the top 5% of their responses to natural images; descriptions written to suppress pushed 97.6% into the bottom 5%. So we now have an automated way to describe the map between neurons and the world — in human language, in the macaque brain. That opens a new avenue: describing biological neurons in the same currency we use to interpret artificial ones, and comparing mechanistic interpretability across brains and AI directly. This work is together with Nikos Karantzas, @kfrankelab @naturecomputes @SuryaGanguli @TamarRottShaham Many thanks to the rest of the team at the Enigma Project @Stanford and @jamesfickel for generous support

If you're at @CVPR this week, come meet the Metamorphic team. We're hosting a happy hour tomorrow evening with @SpiralDB on NeuroAI, AI for Science, and multimodal modeling — and we're hiring. Find @KonstantinWille and @AdrianoCardace there. 👇 metamorphic.com