Bicycling wastes gas?

[jamesqf]

I think what "they say" is usually wrong. There's really not that much difference in the brain's energy consumption when thinking hard and when "not thinking". There' are several reasons for this. For one, a lot of the energy the brain consumes is used just to keep all the neurons alive. They're constantly producing electrochemical signals (action potentials). Thinking is more about changing the signal patterns than increasing the number of signals.

Then there's the ongoing stream of consciousness thinking that really isn't active problem solving. There's also a lot of non-thinking activity going on all the time, for instance the visual cortex constantly processes input regardless of whether you're thinking about what you see.

One thing that does use more energy, though, is long-term learning, since that is actively changing the structure of the brain.

[Christ]

Originally Posted by jamesqf

I think what "they say" is usually wrong. There's really not that much difference in the brain's energy consumption when thinking hard and when "not thinking". There' are several reasons for this. For one, a lot of the energy the brain consumes is used just to keep all the neurons alive. They're constantly producing electrochemical signals (action potentials). Thinking is more about changing the signal patterns than increasing the number of signals.

Then there's the ongoing stream of consciousness thinking that really isn't active problem solving. There's also a lot of non-thinking activity going on all the time, for instance the visual cortex constantly processes input regardless of whether you're thinking about what you see.

One thing that does use more energy, though, is long-term learning, since that is actively changing the structure of the brain.

Something we're obviously not doing in this thread.

[Piwoslaw]

All this thinking makes my head hurt.

[NiHaoMike]

Originally Posted by jamesqf

I think what "they say" is usually wrong. There's really not that much difference in the brain's energy consumption when thinking hard and when "not thinking". There' are several reasons for this. For one, a lot of the energy the brain consumes is used just to keep all the neurons alive. They're constantly producing electrochemical signals (action potentials). Thinking is more about changing the signal patterns than increasing the number of signals.

Then there's the ongoing stream of consciousness thinking that really isn't active problem solving. There's also a lot of non-thinking activity going on all the time, for instance the visual cortex constantly processes input regardless of whether you're thinking about what you see.

One thing that does use more energy, though, is long-term learning, since that is actively changing the structure of the brain.

I always thought that thinking uses more energy because it takes more energy to change states than it does to remain in one state. From my understanding, the brain is not "hard clocked" like a CPU is, but really more comparable to a FPGA. But I'm not sure if it operates similarly to CMOS logic as far as power dissipation is concerned.

[JacobAziza]

Brain on stand by - 6 calories per hour
Thinking hard - 90 Calories per hour

Big difference by %, but not gonna make it as a weight loss routine

Mental Workout | Popular Science

[jamesqf]

OK, it's complicated :-) I'm really over-simplifying a lot, but essentially the brain has constant activity going on, and "thinking" - in which I include everything from ongoing involuntary nervous system activity up to playing chess - is just changes in the patterns of activity. It's the difference between being asleep or unconscious, and brain dead.

But of course there's an easier way to see that thinking doesn't use much energy, by starting from the other end. What happens when you ride a bike, or do any exercise where you're burning significantly more calories that when you're at rest? You breathe deeper to take in more oxygen to burn the calories, your heart speeds up to transport more oxygen &c around the body, if it's warm you sweat a bit because of the extra heat generated by the calories burning. So does any of this happen when you're thinking hard about something?

[JacobAziza]

Exercise your talking about burning an additional several hundred calories per hour.
If you go for a leisurely walk you burn more calories than watching TV, but your heart rate doesn't shoot up and you don't sweat from it.

Every time a neuron fires, it requires energy. Different areas of the brain get activated which were relatively inactive before, depending on what sort of thought it is engaged in. Its not just different patterns, it more total activity (just like you see in all those MRI scans, where different areas "light up")

[Piwoslaw]

Originally Posted by JacobAziza

If you go for a leisurely walk you burn more calories than watching TV, but your heart rate doesn't shoot up and you don't sweat from it.

A few years ago I read that laying down and watching TV requires less calories than just laying down and doing nothing. Something about TV 'hypnotizing' your body (actually - brain) into a less conscious state.

[jamesqf]

Originally Posted by JacobAziza

Every time a neuron fires, it requires energy. Different areas of the brain get activated which were relatively inactive before, depending on what sort of thought it is engaged in. Its not just different patterns, it more total activity (just like you see in all those MRI scans, where different areas "light up")

What you're seeing on those scans are small changes in a large background activity. The brain doesn't (at least according to our limited knowledge) really work like a bunch of on-off switches. It's more of an ongoing chaotic (in the mathematical sense) process. See for instance here: Appraising the brain's energy budget ? PNAS

[roflwaffle]

Originally Posted by Lazarus

Depending on what you eat but here's an Interesting Article

From another forum.

The average price of U.S. gas is $2.66/gallon. We can go 20.36 miles on $2.66 in the average car, how far can we go on $2.66 with a bike figuring 10 mph @ 528 calories an hour.

Their calories/mile estimate for 10mph is way off (double all the mpg/cost estimates), but the basic idea in terms of equivalent cost is correct.