Archive: https://archive.today/jX78a From the post: >>I was really struck by this recent paper, because it gets at a problem that you’d think would have been worked out by now: what is the real biochemical origin of the “tired and need to sleep” feeling, anyway? There have been all sorts of changes noted at the cellular level, but the whole area has suffered from an unshakeable “chicken or the egg” problem (which is a common feature of a lot of biomedical questions, honestly). In this case, are these changes in metabolites, cellular behavior, neuronal firing patterns and all the rest of it the signals that tell you that you need sleep? Or are they just things that are brought on by the need for sleep, and thus downstream of something else? Put more succinctly, are these things causes or consequences? It can be ridiculously hard to answer that sort of question, and for evidence I will reference the question of whether amyloid deposits give you Alzheimer’s disease or whether Alzheimer’s disease gives you amyloid deposits.