Sitting
and thinking doesn’t mean that you are taking it easy. Your brain is using up
about a quarter of the energy output of your metabolism and that energy
consumption is pretty well steady whether we are daydreaming about our vacation
or trying to solve some huge problem on our income tax form.
The
large numbers of fMRI studies show which parts of the brain are getting
particularly excited by different activities and we have got used to this sort
of brain mapping. However, a paper in this week’s Proceedings of the
National Academy of Sciences by Gonzalez–Castillo et al, argues that we are being a little short sighted here (1).
Their
argument is that signal-to-noise levels have misled us to localize the
interactions too much and that although we may have highly activated regions
for particular tasks, very much more of the brain is involved across both
hemispheres giving a much more inclusive picture than hitherto envisaged.
This
doesn’t mean that previous visualization studies are incorrect, just that they
are incomplete as their sensitivities were limited and we should think of more
widely organized activity.
With
the energy consumption being fairly constant as our little grey cells are all
very busy whether we seem to have a thought in our head or not, it is clear
that just thinking hard about going to the gym and eating a more healthy diet
isn’t going to up our metabolic demand and we will just have to get exercising
on the treadmills after all.
