Brain energy expenses

Richard Norman rsnorman at
Thu Aug 17 12:43:51 EST 2000

I believe that the total metabolism of the brain really doesn't change
much between "activity" and "rest".  That is, solving a "difficult"
intellectual problem doesn't use more energy than simply solving the
equally difficult problem of just living.

However, the details of exactly which brain centers are doing the
work changes dramatically, and that is the basis of the imaging
techniques you describe.

And the imaging techniques are nowhere near the resolution of seeing
individual cells, so that the exact "type" of cell involved in the activity
is hard to detect without making electrical recordings from single
cells -- an impossible task to monitor huge number in the brain, not to
mention being extremely invasive.

Perhaps an analogy might be to consider the overall energy use by
television sets during the political conventions vs. during a "normal"
evening.  Specific subpopulations might change their television usage
during this time, and other subpopulations might change which specific
channel is being watched, but the overall energy consumption in a large
city probably doesn't change by a detectable amount.

"Alexandre Blais" <Alexandre.Blais at> wrote in message
news:399C16D5.4ED7E5A8 at
> Dear neuroscientists,
> I am new to this newgroup. I am a molecular biologist and I  am not
> familiar with neurosciences.
> I was wondering if it is possible to measure the amount of energy
> expense (in joules) of the human brain when it is "at work"  (during the
> process of solving a hard problem, for example) compared to its energy
> expense when it is "at intelectual rest" (while watching Wheel Of
> Fortune TV show, for example :-).
> I have done some Pubmed searches, and I found that
> -the main fuel of the brain is glucose, and
> -the energy delivered to brain cells is derived from oxidative
> metabolism of glucose, glycogen breakdown, and from the tricarboxylate
> pathway
> -the main method of evaluating the metabolic activity of the brain is
> via MRI and PET using analogs of glucose
> -it is possible to evaluate the contribution of different celle types in
> the brain, and to analyze the metabolic activity of different parts of
> the brain
> -researchers notice an increase in metabolic activity following
> "stimulation" of different parts of the brain
> However, I found no papers describing and measuring the total energy
> expense of the brain during "intellectual work" per unit time. May be my
> question is naive and this type of experiment can not be attempted ?
> Just let me know .
> If someone can enlighten me on that topic, or can direct me to some
> useful resources, I would be very greateful,
> Alexandre Blais
> Centre de Recherche du CHUL
> Québec, Canada

More information about the Neur-sci mailing list