An image of the brain processes created from the metabolism of neurons. There are three types of fMRI imaging, which use blood flow, blood volume and blood oxygenation level-dependent (BOLD) signals. The BOLD method is the most common method used as it has the highest functional contrast. As the brain regions are engaged in a task they require more blood. The fMRI is an image of changes in blood flow based on task demands. The fMRI is one tool being researched to find central nervous system indicators of deception. See: Kozel, Johnson, Grenesko, Laken, Kose, Lu, Pollina, Ryan & George (2009); Pollina, Horvath, Denver, Dollins & Brown (2008).