Brain Box has posted an accessible explanation of what fMRI brain scan devices actually measure.
“At its best, fMRI provides unparalleled access to detailed patterns of activity in the healthy human brain,” states Brain Box. “At its worst, fMRI could reduce to an expensive generator of 3-dimensional Rorschach images. To understand the relative strengths and weaknesses of fMRI, it is essential to understand exactly what fMRI measures.”
What does fMRI measure? (Brain Box, May 15, 2015)