Main points are that brain takes ~20% of body's Base Metabolic Rate, and that active thinking takes 5% more than BMR.
Whole body context: - Base Metabolic Rate (awake): ~1.0-1.1 kcal/kg/hr - Deep Sleep Metabolic Rate: 0.8-0.9 kcal/kg/hr
CG says brain follows this as well.
So it suggests brain power use varies from 0.8 minimum to 1.1, with an extra 0.05 for thinking. This supports ideas that thinking is a relatively minor brain function, at least energetically.
Anecdata, but I remember writing software for a startup and getting thirsty. We had a fridge that had all sugar-free sodas because one of the founders was diabetic. I remember drinking a soda and still feeling really thirsty. Drank another and still didn't solve it. It finally dawned on me that my brain just really wanted the sugar for the easy calories, and the sugar-free soda obviously wasn't fixing this at all. Thinking hard definitely burns calories faster than not.
> they concluded that effortful, goal-directed tasks use only 5% more energy than restful brain activity
That parallels the other conclusion that we don't really use that much more energy when at rest and when exercising. If energy isn't used by movement, it gets used for whatever to consume the predetermined daily energy budget.
Our bodies seem to be really set up to work with a consistent fixed energy amount and dealing with allocation of it instead of optimizing idle efficiency. We don't idle.
...the majority of the brain’s function goes to maintenance
Makes sense. Same for large software projects, my boat, house, etc.
> Theoretically, the top speed for a neuron to feasibly fire and send information to its neighbor is 500 hertz. However, if neurons actually fired at 500 hertz, the system would become completely overwhelmed.
> Our neurons, however, have an average firing rate of 4 hertz, 50 to 60 times less than what is optimal for information transmission.
Could this explain the time dilation you can get when under high stress - is this your brain just firing as fast as it can?
Fun fact: when it is cold, and you need more heat inside you, it doesn't take any energy at all. In fact nothing takes energy, except physical work.
The same is true for households, if it's winter, and you have the heating on, washing clothes, cooking, mining bitcoin, they are all free, since every Joule metered in the electricity meter converts to heat.
Fun facts, brain consumes about 20-25% of body's total energy despite being only 2% of the body's mass.
I'm very surprised the article and also the corresponding paper on human energy didn't even mentioned the crucial role of mitocondria but ironically related linked article on mitocondria at the bottom of article (perhaps based on the magazine recommendation algorithm) does points to it [1],[2].
[1] Mitochondrion:
https://en.wikipedia.org/wiki/Mitochondrion
[2] ‘Turbocharged’ Mitochondria Power Birds’ Epic Migratory Journeys:
https://www.quantamagazine.org/turbocharged-mitochondria-pow...
Is there a drug that can overclock the brain from 4Hz to like a 100Hz? Since up to 250Hz is fine, that's well within, right?. Sure that'd make me burn at least 100/4*20%=5 as many calories (probably in sugar), but that's something I could provide with soda and cookies for a day.
Maybe start by asking what does it mean to think?
From the article: "Jamadar’s analysis showed that a brain performing active tasks consumes just 5% more energy compared to a resting brain. When we are engaged in an effortful, goal-directed task, such as studying a bus schedule in a new city, neuronal firing rates increase in the relevant brain regions or networks — in that example, visual and language processing regions. This accounts for that extra 5%; the remaining 95% goes to the brain’s base metabolic load."
To me it is fairly obvious that those tasks are not what creates the highest loads on the brain. The "thinking load" from active, in-person, social interactions is much higher.
If our brains are energy misers, maybe the real supercomputers are the ones that can do more with less—not the ones with the most flops. This could reframe how we design efficient algorithms and even AI: sometimes, the best strategy isn’t processing power, but predictive efficiency.
Maybe the next breakthrough in cloud computing isn’t more cores or larger GPUs, but better energy allocation and anticipation, just like the brain.
I think there should also be a measure of how you think. It would seem plausible to me that a fields medalist would use considerably less energy to come up with solutions to general problems in math than someone else.
What about how much energy is needed to not to think? Some people that struggle with overthinking, the approach of thinking definitely is different from how we think when working on something. So is the energy used is different as well?
"Thinking" covers a wide spectrum of activity and intensity, no? I glanced through the references and the only tasks I found were Tetris tasks.
A weird thing I've noticed that I've never seen discussed anywhere is that when kids are concentrating / thinking hard, they start breathing heavily. I wonder what is going on with this.
Random thought: what LLMs do may be just a tiny fraction of what real brains do, so artificial reasoning is probably a much easier problem than an artifical brain.
Accumulation of cerebrospinal fluid needs to flush waste from brain operation hence the need for rest/sleep.
It is part of why people argue that Chess is a sport.
When grandmasters battle it out for hours in classic chess, thinking ahead of so many branches of moves that I would find unfathomable, they do burn through a lot of energy.
For what is quite a sedentary career choice, I rarely see overweight grandmasters. Though that is probably more correlation of other facts than causation...
I was sort of hoping they'd give an actual wattage figure of how much energy the brain uses, but sadly they don't
Less than it takes an LLM to infer
On a related note, the impact of "things" - everything, from inflammation from stress or less sleep or long covid/me/cfs to the effects of ibuprofen or creatine or methylene blue - is staggering.
Anyone who's taken any kind of brain medication that has worked (be it SS/NRIs or DNRIs or antipsychotics or stimulant medications) can tell you how much of what we think "we are", is significantly affected by neurochemistry (amongst a lot of other things too!)
I am not sure how much someone who hasn't experienced it (themselves or via a family member/friend) can really appreciate, and I wish for people to be more cognizant and supportive in general, rather than being judgemental or going "I could do it, why can't you?"
Since the brain is optimized for low energy environments, and we have now reached a high energy availability era, it makes you wonder if there's a way to get around the mental fatigue problem somehow. Fatigue is incredibly intellectually debilitating and if we could find a way to be fully on all of the time if we so wish, that should come with a great increase in quality of life.
Now available energy is almost certainly not the only reason we have fatigue, so maybe there's other barriers to overcome, but I'm shocked at how little attention this topic gets. In hackernews spirit, if someone could sell a real cure for mental fatigue, you'd change the world