An excerpt from an OUPblog article published on 16th September 2016, written by Richard Passingham, author of Cognitive Neuroscience: A Very Short Introduction.
'Functional magnetic brain imaging (fMRI) is a method that allows us to study the workings of the human brain while people perceive, reason, and make decisions. The principle on which it’s based is that, when nerve cells or neurons in a particular region become active, there is an increase in the blood supply to that brain area. This can be visualized because the scanner can be sensitized to the changes in the blood oxygen level that occur when the nerve cells become active.'
Discover more: Read the rest of the article on the OUPblog.