Could depression arise from a fundamental problem with prediction?

Here is a long post from Scott Alexander at Slate Star Codex . . . I feel that is a redundant phrase, since as far as I can tell Scott Alexander does not write short posts about anything . . . but though it may be a little tl;dr for some of you, I thought it was very interesting.

You should be aware before going in that Alexander is a psychiatrist and this is a kind of technical post that assumes you have read other recent posts. But I haven’t read those and I’m not a psychiatrist and I found this post understandable and intriguing.

[I]f the brain works to minimize prediction error, isn’t its best strategy to sit in a dark room and do nothing forever? After all, then it can predict its sense-data pretty much perfectly – it’ll always just stay “darkened room” . . . I notice that this whole “sit in a dark room and never leave” thing sounds a lot like what depressed people say they wish they could do (and how the most severe cases of depression actually end up). Might there be a connection?

Alexander is referring here to a theory of how the brain works, called predictive processing, which says, in a nutshell, [Your brain’s] goal is to minimize surprise – to become so good at predicting the world (conditional on the predictions sent by higher [cognitive] levels) that nothing ever surprises them. Surprise prompts a frenzy of activity adjusting the parameters of models – or deploying new models – until the surprise stops.

So Alexander says, applying this to depression, Depression has to be about something more than just beliefs; it has to be something fundamental to the nervous system. And low confidence in neural predictions would do it. Since neural predictions are the basic unit of thought, encoding not just perception but also motivation, reward, and even movement – globally low confidence levels would have devastating effects on a whole host of processes.

It goes on from there, and as I said, this post contains stacked concepts that may lead you off to read about fifty pages of text in order to develop a really coherent idea about what Alexander is talking about. If you find the subject at all interesting, this should prove time well spent. It’s fascinating stuff, and Alexander has a knack for putting abstruse things in pretty understandable terms.

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