Biology Question #4612

Alexandra, a 17 year old female from Coquitlam asks on March 20, 2009,

What are thoughts made from? Are they measurable?

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The answer

Barry Shell answered on March 20, 2009

Nobody really knows. Thoughts are believed to be a combination of changes in electrical potential and very small chemical changes, but nobody knows for sure. Since nobody knows what they really are, there is no way for certain to measure them, because what do you measure?

Nevertheless scientists have done a tremendous number of experiments measuring things in the brain and then seeing if they can make any connection between those measurements and "thoughts". Some things that can be measured are the very small electric currents or magnetic fields produced by the brain. You can learn more about this on Wikipedia: Electroencephalography, Magnetoencephalography.

Another way is with a PET scan or a FMRI scan, which measure the result of small chemical changes, usually the brain's rate of usage of sugar from the blood. This works by putting some special chemical into the brain--usually a kind of modified radioactive sugar that you get via a needle in the arm--and then watching as this sugar is 'burned' in the brain. This can show what part of the brain is most active perhaps when you are thinking a certain thought. Many experiments of this type have been done and many are going on right now. Wikipedia pages on PET (Positron emission tomography) and FMRI. Everyone would like to know what thoughts are made of, but so far this question has eluded science, except via rather crude forms of measurement.

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