I think it's from lyra's neuron-explorer project https://x.com/_lyraaaa_/status/2113833330429083662 (see also https://neuronary.org/about, https://github.com/lyramakesmusic/neuron-explorer)

There was a paper that popped up a month or two ago (I think published earlier though) about being able to inject "thoughts" into the neurons. E.g. Ask it what I should eat, and steer it towards "bread".

Are you thinking of this one?

https://www.anthropic.com/research/introspection

About halfway down they inject bread into its head.