Don't Be So Quick to Flush 15 Years of Brain Scan Studies

The most sophisticated, widely adopted, and important tool for looking at living brain activity actually does no such thing. Called functional magnetic resonance imaging, what it really does is scan for the magnetic signatures of oxygen-rich blood. Blood indicates that the brain is doing something, but it's not a direct measure of brain activity. Which is to say, there's room for error. That's why neuroscientists use special statistics to filter out noise in their fMRIs, verifying that the shaded blobs they see pulsing across their computer screens actually relate to blood flowing through the brain.