What is the neuroscience of hallucinogen-persisting perception disorder (HPPD)?
I'm not a neuroscientist, but there is a very interesting article in the NY Times that has some interesting hypotheses about what is happening: http://www.newyorker.com/tech/el...Here's what one reseacher says:“What we have proven through psychophysics, electrophysiology, and quantitative analysis,” said Abraham, “is that when the brain of an H.P.P.D. person is stimulated by some perceptual force in the environment, mostly visual, the stimulus is disinhibited.” Objects of perception, in other words, are not readily disengaged, breaking up an ordinarily seamless flow of conscious experience. If the brain is like a paintbrush, then H.P.P.D. appears to make the bristles sticky, and the old stimuli—colors, shapes, and motions—muddy the new. And:A healthy brain, Biederman explained, is bathed in inhibitory neurotransmitters—gamma-aminobutyric acid, primarily—in order to mute mild perceptual noise (like visual distortions), and ultimately to safeguard against full-blown cacophony (like seizures). H.P.P.D. patients, he offered, might have “done something structurally to those interneurons, causing perceptual noise to exceed the threshold.”
Is hallucinogen persisting perception disorder similar to schizophrenia?
Yes, definitely. Specially those which change how you perceive the ego.Basically, hallucinogens, especially psychedelics, mean psychosis like state. So, that drug users are experiencing as they were in a psychotic state. Schizophrenia is a long-term psychotic disorder. It is interesting because it is one of the disorders that change the strict balance between ego and consciousness in long term. In schizophrenia your mind is working as usually but your ego is fragmented and at times you can access those fragments. This makes a patient to feel either disconnected from environment or being a center of everything. Delusions come because it is hard to distinct what is real and what is not - ego seem to be in a key role in constructing a linear feeling of the world. Those fragments can also manifest to scary experiences because one cannot identify them as part of one's ego, and sometimes it might feel that there are multiple egos at once (usually characterized as schizophrenic voices). Schizophrenia is hard to study because it is unknown what is actually happening in patience's mind. However, there are drugs that can manifest similar feelings as schizophrenia that allow researches to study schizophrenia like state in a controlled laboratory setting. One widely studied drug is LSD which is very powerful and can manifest closely related effects to schizophrenia. You can read more about LSD from my another answer, Jussi Raunio's answer to How do hallucinogens affect brain chemicals? However, I must point out that hallucinogens can manifest also more and different effects that are presented in schizophrenia. Also, hallucinogens can cause underlying schizophrenia or psychosis to manifest if the drug user has a genetic tendency to it.
Is hallucinogen persisting perception disorder a special case of sensory processing disorder?
Hallucinations caused by a psychotic state either manufactured or naturally occurring are a new place in which the person or animal finds himself. Place is more or less everything in existence, place is fundamental to dimension but not defined by dimension. Space is place, there are dimension in space but space has no dimension. And it is exactly this situation where the organism finds itself , " a place without dimension". So the organism gearing up for survival is intent on reckoning one. No man is an island so others in a close proximity can be taken into the hallucination too, but not to the same extent. Rasputin was good at it, many others too, that's the practical level, concerning the mechanics that cause hallucination we are best to consider the question of perception causing perception, isolated from conception. That's the real Universe we live in, which is made from the reality that preceded it, as a matter of course. I could type on that all day, but it would be to no avail, because, did that other commentator mention 20 years, I got my doubts about that.
Short question about hallucinogens?
From mental health point of view, if you consider, basically it requires lot of physical self-discipline and mental control. According to me remedy for self-inflicted problems have to be found by individuals. They should use their ingenuity and intellectual brilliance. Self help is the best help. In future if you nurture healthy and wise thoughts, habits, traits, behaviors, ideas and feelings in your mind, then it may be possible to overcome such tough problems. Moreover, everything depends on your sincere and honest approach with dedication.
Home made hallucinogen?
Nutmeg is a hallucinogen in large doses. It was used by poor hippies in the 60's. It was called the poor man's LSD. The trouble is, the dose for hallucination is just a hair smaller than the fatal dose. Nutmeg poisoning has no antidote. The only solution is keeping the patient on life support until all the nutmeg is purged naturally.
Could co-administering psychedelics (like LSD) with neuroplasticity-increasing agents (like valproic acid) increase the chances of developing hallucinogen persisting perception disorder or psychedelic-induced psychosis?
HPPD is a complete non-disorder imo (personally I love having psychedelic vision) and examples of people experiencing genuine psychosis from a psychedelic (not just a bad trip) are so vanishingly rare.....