Comment by robotresearcher

Here's a neural network concept from the 90s where the neurons are bathed in diffusing neuromodulator 'gases', inspired by nitric oxide action in the brain. It's a source of slow semi-local dynamics for the network meta-parameter optimization (GA) to make use of. You could change these networks' behavior by tweaking the neuromodulators!

https://sussex.figshare.com/articles/journal_contribution/Be...

I'm not an author. I followed the work at the time.