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Comment by clankfan | Hacker News Reader

Hasn't it been reported that psychosis is caused by a lack of connectivity in the brain? I seem to remember someone saying that there had been a breakthrough in discovering that certain brain cells were pulling double duty as immune cells and overzealously pruning connections, causing psychosis.

If over-connectivity is the source of all these problems then isn't that a boon because it must be simpler to cut connections therapudicly than to create them

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Those are two different kinds of connectivity.

The first is about synapse density, the second about how strongly different parts of the brain are linked together (relative to one another).

So a brain with a low average synapse density may still have some areas more functionally connected than the average population.

The default mode network and the attention-related fronto-parietal networks are usually disconnected functionally, they inhibit one another.

See https://en.wikipedia.org/wiki/Dynamic_functional_connectivit... for details

There seems to be some thought that it could be under/over connectivity, based upon conditions and symptoms (one of a million theories). I don't know necessarily if more connections can be solved so easily - there's the question of how to keep them from growing back in the same pathological manner, and then also which ones to cut. "Well, this neuron either kills your fear of dogs, or your awareness of the number 5."

also "psychosis" could be better defined. The visuospatial perceptual+ memory errors of an Alzheimer's patient probably very different neurophysiology from hallucinatory phenomena of a schizophrenia patient, for example

If psychosis was due to irreversible brain damage per se, then it wouldn't be possible for it to come and go. Episodes might do cumulative damage, but the difference between being in an episode and not being in an episode can't be caused by something irreversible.

I don't think the root cause(es) of psychosis have really been determined yet. I think it's fair to say that since many drugs induce immediate psychosis, it's unlikely that pruned connections are the only cause.

It’s pretty clearly D2-like receptors being overexcited, at least as far as cause and effect. Hence psychotic symptoms in stimulant users and a remission of psychosis in schizophrenic patients when on D2-blocking drugs.

D2 receptors are undoubtedly tied to many forms of psychosis, but their being the root cause is not yet proven.

Psychosis resulting from meth withdrawal has always suggested to me that it is an under-connected problem because presumably what happens during withdrawal is widespread "disconnection" resulting from a large decrease in synaptic sensitivity (caused by a flood of neurotransmitter, meth) and a steep drop in neurotransmitter activity once the meth is gone.

Stimulants shred the cells' mitochondria. Psychosis is a metabolic problem.

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