MODEL RELEASED. Dopamine research. Study into the abundance of dopamine D2 receptors in the brain (red/blue). The colours of the brain on the computer image indicate the relative amount of receptors. Dopamine is an abundant brain chemical which helps control muscle movements and thought processes. Here, the brain was exposed to a radioactive dopamine analogue. This bound to the receptors, and the radioactivity caused darkening of the photographic film it was held against. Dopamine research is largely aimed at diseases in which there are abnormal levels of the chemical, such as Parkinson's disease and schizophrenia.