why they thought the deep-dream images seemed, in the buoyant phrasing of the Chambers Brothers, psychedelicized.
Inside Deep Dreams: How Google Made Its Computers Go Crazy
Steven Levy

I think I recall some research from the 1960s to the effect that psychedelics inhibit transmission at the thalamus, the neural relay station between the eyes and the visual cortex, so that the sensory input has less effect on one’s experience — and one’s internal (more primitive, idealized, emotionally charged) images have more effect. At first thought, this was counter-intuitive, because the psychedelic experiences are so sensuous and vivid. But on second thought, perhaps it shows that the richness and aliveness comes from within, and the optical input has the more mundane job of keeping us constrained by everyday practicalities. Whatever: Mordvintsev’s neural nets seem to be tilting the balance of inner vs outer influences in the same way that psychedelics did in our wetware — and with similar effects on the resulting experiences.