Neurons

Every MLP neuron in Qwen3.5-4B, one pixel each: 32 layers × 9,216 neurons, 294,912 in all. Each neuron has two directions, steered up and down at dose ±1, and the quick scan scored both. A pixel shows the furthest state either direction has reached; hover it for both. The colors are bookkeeping, where a neuron stands in the screening funnel, and say nothing by themselves about whether it matters.

Click a pixel to open its specimen page (shift-click for the other direction); on a touch screen, tap once for the profile and again to open it. Click a legend entry to light up only that state.

Named specimen group28 neurons

What each state means

■ Unscreened. No quick-scan row: this direction has not been through the KL screen. 0 directions; 0 neurons show this state.
■ Quick scan · quiet. Screened; KL in the lowest 25% of its own layer (KL rises with depth, so the cutoff is per layer). The next-token distribution barely moved. 201,247 directions; 33,201 neurons show this state.
■ Quick scan · broken. Screened; KL above 2.5 or top-1 agreement below 0.3, the site's cutoffs for a distribution that is mostly wrecked. 86,200 directions; 40,703 neurons show this state.
■ Quick scan · middle. Screened; not quiet, not broken, and outside the promotion band. 165,183 directions; 107,176 neurons show this state.
■ Quick scan · in band. Screened and inside the quick scan's promotion band (KL 1 to 2.5, top-1 agreement 0.5 to 0.65): eligible to be sampled into the short test. Eligible is not chosen; the band is sampled at random, one direction per neuron. 134,357 directions; 111,479 neurons show this state.
■ Stopped after the short test. Ran the short test and did not pass its decision (score at least 0.36 and drift at least 0.32). Stays on file. 504 directions; 504 neurons show this state.
■ In the short test. Asked to run the short test (a small prompt subset): queued, running, or waiting for its decision. 1,024 directions; 1,024 neurons show this state.
■ Stopped after the longer test. Ran the longer test and did not pass its decision (interest at least 0.38). Stays on file. 84 directions; 84 neurons show this state.
■ In the longer test. Passed the short test and has been asked to run the longer test: queued, running, or waiting for its decision. 40 directions; 40 neurons show this state.
■ Full test. Asked to run the full test (every prompt): replies are in or queued. Includes specimens that went straight to the full test before the tiers existed, and single neurons run at other doses. 1,185 directions; 701 neurons show this state.
◯ Named specimen group. A slowly pulsing ring (a still ring if your system asks for less motion) marks every neuron that belongs to a named specimen group: the 7 specimens Kyle has named, and the other 38 hand-picked specimens of kind named (mostly neurons taken from an outside list, the Qwen neuron zoo, which carry its label and a GLM name). Neurons that only have a GLM name are not marked. Several neurons can share a group; a neuron can belong to more than one.

Directions are ranked by how far they got: unscreened, then the three quick-scan outcomes that go no further (quiet, broken, middle), then the promotion band, then the short test, the longer test and the full test; at the same test, a specimen still in it ranks above one that was stopped there. A neuron takes the highest of its two directions. The funnel's own page, Method, has the numbers behind each test.