A magnetic resonance imaging (MRI) system is an expensive piece of lab equipment, especially the new generation of high-field systems, but man can they do some amazing stuff. I sat in on a General Electric luncheon in Toronto earlier this spring and was floored not just by the quality, but the applications of MRI. So, how does one go about using MRI to investigate what we call love? This is a special application of MRI called functional MRI, or fMRI for short. The ability to detect brain activation comes from a peculiar decoupling of neuron function and blood flow. What I mean by this is that when the inputs to a neuron from other neurons (delivered by connections between neurons called synapses) cause it to activate and transmit a current down the axon and be the input to the next neuron. This activation of a neuron results in membrane depolarization (ion gradients across membranes, which are kept high by ion transport proteins in the cell membrane, equalize, resulting in electrical transmission down an axon) an increase in metabolism, as it tries to recover the electrical potential across cell membranes. That is, glucose and oxygen usage rise sharply upwards. Local blood flow is sensitive to neuronal activation and increases to meet the increased demand for oxygen, but actually overshoots the requirements of tissue.