I'm curious to know how much energy a brain will use depending on the different activities it's doing. Sleeping vs. watching TV vs. doing rigorous physics problems vs. running a marathon For the above activities, what are the different energy requirements like? How do the things you're thinking about translate into energy usage? I assume the more active your brain is, the more electron transfer there will be, which means more energy will be required. I don't know details for any of this.