No, it's definitely in study and a lot of computational models of how these mechanisms may work were put forward. Most definitely it has to do with "to stop so

No, it's definitely in study and a lot of computational models of how these mechanisms may work were put forward. Most definitely it has to do with "to stop something harmful to happen to the brain" but since the brain is such a huge interconnected mess, it's difficult to make a grand statement. An analogy with weight-lifting (or long-distance running) is easier: when you are lifting weights sometimes you reach failure and you think you can go no further, but usually this is a message having to do with the body parts you are exercising just being to hot... some weight-lifters quickly cool down the palms of their hands (under the arms, under the feets, etc...) and can continue lifting. Is very simple, you don't want to cook yourself, but the message that we consciously feel is akin to, "I can't go no more" when instead by lowering body temperature, you can come back. So one factor, definitely, is temperature (you don't want your brain to get too hot) but also is the rate at which you can recreate new neuronal connections (when learning for example. And what are the constituents of these new neuronal pathways? Do you also delete?) These are only two factors and there has to be a whole panoply of them (electrolytes, vitamins, glucose, dopamine, etc...)