These two images of the brain are Positron Emission Tomography (PET) scans from a normal person (picture on the left) and from a person who abuses cocaine (picture on the right). The PET scan shows brain function by seeing how it uses a sugar called glucose, the energy source for all cells in your brain. In these scans, the red color shows high use of glucose, yellow shows medium use, and blue shows the lowest use of glucose. It is easy to see that the brain of the cocaine user is very different from that of the normal person and uses glucose much less efficiently (Cocaine, 2007).