MadSci Network: Neuroscience |
You asked a very tough question. Unfortunately, the brain isn't quite like set of lightbulbs that you can switch on to use it and off when you're done with it. The brain is always active, even when you're asleep. Different parts of the brain may be more or less active depending on what you're doing at the time. Perhaps these two pieces of information will help.
1)The brain uses about 20% of the oxygen and 15% of the blood flow in the
body, even though by size it contains only about 2% of the weight.
(obviously not all tissues are equal). Also of that energy, most of it
(60%) is used to maintain the proper concentrations of ions inside and
outside the neurons. It is these different concentrations of ions that
allow neurons to send electrical signals to each other (so obviously
they're very important). The rest is used for cellular 'housekeeping'.
2) One way of understanding which sensory systems are most important to an
animal is to look at the amount of brain space devoted to processing of
that information. For example, humans are very dependent on visual input,
and about 1/3 of our brains are used for processing visual information. In
other animals, for example dogs, olfactory information (smell) is more
important, and much more space in the brain is used for processing smell
than for say vision.
I hope this helped. If you give me a better idea on what your science fair topic is about, perhaps I will be able to answer your question better.
Try the links in the MadSci Library for more information on Neuroscience.