I watched a program on PBS back in the mid 80's about San Fransisco and the Haight Asbury Free clinic. They were speaking with a doctor about "acid casualties"

I watched a program on PBS back in the mid 80's about San Fransisco and the Haight Asbury Free clinic. They were speaking with a doctor about "acid casualties" LSD. What the doctor said was really interesting. People who have flashbacks get scared thinking their brain is fried, and it's usually triggered by something visual. The patients have visual "abnormalities" and it scares them into thinking a new acid trip will start. In reality what LSD, Mushrooms, Peyote, etc. can do is strip away all the adaptations in the visual system. He said in most cultures that use psychedelics they usually talk about cleansing, or stripping away when using psychedelics, and with the visual system it's a true statement. When he went on to say was that when we are born our visual system is like a blank downloadable computer, and as we grow, the visual part of our brain is making adaptations based on what it knows vs what is 'senses'. He said that due to small eye movements the sensing would jiggle, especially in our peripheral vision, but we learn the the world doesn't jiggle, so the visual system makes sure that stable items don't jiggle. Tons of adaptations take place, depending on our lives and experiences some of us have more adaptions than others. Sometimes when taking psychedelics all those adaptations get stripped out, or only some get stripped out, leaving people with the untrained system, and that untrained system doesn't present things in the same way. Colors don't look the same, sometimes things in the peripheral vision jiggle or move, moving our heads quickly while quickly moving our eyes can cause 'trails'. All indications that our visual system has had some adaptations erased. The doctor said that eventually over time things get usually restored to normal. However he said for colors, it's interesting because for people that grew up in a different area of the country and had their color perception set at that location, they sometimes find the when wipe out the adaptions and reset things the colors sometimes don't matched. Depending on where they grew up vs where the adaptations get reset the color of the sunlight can be different, and that will alert the color adaptation.