I study how the brain works, especially memory and how we find our way about in the world. One of the techniques I use is magnetic resonance imaging (MRI). An MRI scanner uses a strong and precisely-controlled magnetic field, together with radio waves, to create a detailed 3D image of the brain. You can use this to measure the size of different structures in the brain, and we sometimes find the size of certain brain structures relates to how well people can do particular tasks.
MRI scans are very useful in themselves (e.g., doctors use them to diagnose and treat disease and brain injury), but functional MRI (fMRI) is even more useful for finding out how the brain works. It is a way of tuning the scanner to be sensitive to small changes in blood flow. When part of the brain is busy, it uses up oxygen, and this leads to an increase in blood flow in the active area. So we can find out what different parts of the brain are doing by comparing blood flow changes we see as a person in the scanner switches between different tasks.