“We see with the eyes, but we see with the brain as well, and seeing with the brain is often called ‘imagination,’ and we are familiar with the landscapes of our own imagination, our ‘inscapes,’ we’ve lived with them all our lives. But there are also hallucinations as well, and hallucinations are completely different…they seem to come from the outside, and to mimic perception.” With those words, world-famous neurologist Oliver Sacks begins a fascinating twenty-minute talk on hallucination, which you can watch in its entirety below. Sacks is well-known for his work in neurology, and you’ve probably seen the movie Awakenings (starring Robin WIlliams as a character based on Sacks) — that film was based on the true story of how Sacks discovered how to revive catatonic patients with a new drug called L-Dopa. Anyway, back to today’s Sacks talk.

Discussed: visual hallucinations among the visually impaired, hallucinations as “a rather boring movie,” Charles Bonnett syndrome, handsome young men who disappear in a flash, hallucinations of Kermit the Frog, why Kermit?, temporal lobe epilepsy (”time travel” style hallucinations), the special part of the brain activated by cartoons, how the mind may treat hallucinations as dreams, and finally, “Kermit means nothing to me!”

If your computer is up to the task, you may want to watch the talk in high-resolution MP4 — much bigger and shinier.