There was an early visual neural network demonstration — strong feeling it was called "Yorick" or somesuch as it was built in a plaster skull — that had a square grid of red LEDs to show its output state as a simple picture; when its camera was unplugged the neural network appeared to "dream" in the sense that things it had seen would flicker and swirl in the output.

I saw this in a video in the early 90s and cannot remember where.