I've always found Retinal Waves[1] interesting. During development of the visual system, there are spontaneous bursts of activity without external stimuli, helping the synapses to organize properly.

In my layman's view, it's like hallucinating shapes that are important to learn. Very similar to the "priming" described in the article, but easier to visualize (literally).

[1] https://en.wikipedia.org/wiki/Retinal_waves