[stinos]

we don't see anything like that

Yes we do. For quite some effects seen in patients in psychiatry it's not too hard to come up with a drug which induces similar experiences. Take paranoia for instance. And hallucinations of course. Or, to mention an extreme and very rare example: there are people lacking a certain connection between the low-level visual processing and the parts translating that to known objects (sorry, don't remember exact terminology). It's extremely hard to imagine, but such people have normal vision yet they do not recognize based on what they see. E.g. they see a chair, but don't know it is a 'chair'. However when they touch the chair they know 'aha, chair'. Someone I know described that exactly once when on psychdelics; psilocybin IIRC.

[MikkoFinell]

If the hypothesis was true, we would expect the effects of brain damage to reliably create a richer and more psychedelic experience for the sufferer. Hallucinations and paranoia are only a tiny subset of the effects experienced by people on psychedelics, so logically the only part of the hypothesis that becomes more probable is that the brain usually filters out hallucinations and paranoia. But I won't accept that either, because neither brain damage or psychedelics reliably produce paranoia, and brain damage does not reliably produce hallucinations.

I don't rule anything out, but the filter hypothesis seems a lot less likely to me given the evidence, than the simpler explanation: That psychedelics just mess up the normal functioning of the brain to create a different experience. This requires less assumptions than the filter hypothesis, which is akin to suggesting that the brain is actually drunk all the time, but alcohol merely removes the filter to allow us to experience the drunk phenomenology.

[stinos]

Note I'm not claiming the filtration theory is true or false - I also have doubts about it - I'm just saying your rejection of it based on 'we don't see such effects because of brain damage ergo the theory doesn't hold' isn't exactly sound. Actually I'm not sure you can use brain damage to prove anything here. It's also too general of a term for me. As far as I'm concerned a serious head trauma where part of the brain is removed as well as a lesion applied locally for the purpose of neurophysiological research are both brain damage.

If the hypothesis was true, we would expect the effects of brain damage to reliably create a richer and more psychedelic experience for the sufferer.

Why 'reliably'? Not all brain damage is the same. Maybe I'm misunderstanding the theory but I don't think it argues that, nor is it what happens in reality.

Also, why at all? Why would certain brain damage not be able to create a less rich experience? The theory doesn't say that is impossible I think?

[MikkoFinell]

I'm not saying that filtration theory is false, I'm saying it seems less likely to me than the following alternative: The chemical composition of a sober persons brain causes us to have the usual experience, but taking a substance like psilocybin alters the chemical balance and therefore makes us have unusual experiences. It seems like I have to suppose more assumptions under filtration theory, and that those new assumptions are unfounded and that the consequences of accepting filtration theory leads to predictions that aren't true (vis a vis brain damage).

Which brings us to why I tried to make the point about brain damage. Since we are working with the idea that psychedelic experience is the default but that the brain is filtering out most of it, it seems to follow that strategically damaging the filter should allow psychedelic experiences to flow through. You're right, not all brain damage is the same, but enough people suffer similar brain damage that I believe we ought to have seen by now some subset of patients with certain types of trauma reliably report psychedelic experiences as part of their symptoms. If such a subset exists, then I stand corrected.

[stinos]

enough people suffer similar brain damage

Problem is that is quite hard to assess if it is sufficiently similar. That alone warrants an entire range of experiments. Also I don't know the literature enough to figure out if certain types of trauma reliably lead to similar experiences but I do think that is the case. For example electrical stimulation (not 'damage' per se but definitely altering the normal brain operation in subjects) has been repeatedly used to treat a myriad of problems like tinitus, tremors, ... And I know for a fact that during surgery, when attempting to find the right position for the electorde, it is not uncommon for patients to experience hallucinations/strong feelings of disgust/... because stimulating in the 'wrong' area instead of the proper target area. Also look at lobotomy for instance: quite a lot of similar symptoms in the unlucky subjects. Again: doesn't really prove filtration, but does indicate what you think doesn't happen (ie.strategical damage causing similar experiences) does in fact happen so it's imo not a good measure to reject the hypothesis.

[xamuel]

The brain damage caused by psychedelics is extremely specific. By your logic, tonsillitis shouldn't be curable by removing the tonsils, because if it were, then shooting someone in the mouth with a shotgun ought to produce similar effects to performing a tonsillectomy.

[MikkoFinell]

Sorry but I don't see how that follows from my logic at all. Would you please care to clarify how you reached that conclusion starting from some assumption I made?

[Retric]

Brain trauma is inherently more localized than drugs, so expecting a 1:1 mapping is hardly reasonable.

However, fever lack of sleep and other non localized effects can produce a wide range of Hallucinations.

[MikkoFinell]

I agree that fever and lack of sleep can produce hallucinations, but I'm not convinced that they are non-localized effects in the brain, nor that psychedelic chemicals are non-localized in the brain.

[Retric]

How do you think the temperature increase from Fever could be localized? It's just a temperature increase and you can induce the same effects by preventing the body from cooling down effectively.

[MikkoFinell]

I meant the effects of fever, so that perhaps different parts of the brain was affected differently by the temperature increase. I really have no idea, but I was saying that it is not an obvious fact either way.