Asked by: BBC Focus magazine
Functional Magnetic Resonance Imaging (fMRI) shows what the brain is doing, as well as how it looks. Volunteers in fMRI experiments typically carry out a cognitive task, such as responding to stimuli, or calculating, recalling, or imagining something. Meanwhile, the scanner measures the blood flow to and from different parts of the brain and superimposes it onto an anatomical picture of the brain. The areas pulling in most blood are assumed to be those that are most active. This is because blood carries oxygen, which is the ‘fuel’ that brain cells use to generate electricity.
fMRI is the most common technology used to correlate brain activity with our thoughts, responses and perceptions. It seems to be safe and it’s good at pinpointing location. Other techniques, such as non-invasive EEG, in which scalp-mounted electrodes detect signals from the underlying brain, are faster but less precise.