False-colour positron emission tomography (PET) scan highlighting limbic areas in a human brain. A receptor for the inhibitory neurotransmitter GABA is visualised here in regions of the brain associated with memory, learning, emotional processing and addiction, where levels are high. Colour is proportional to signal strength, with blue representing low receptor density, through to red representing high receptor density. This has been superimposed on a transparent structural representation of the brain. In this orientation, the brain is facing to the left and slightly toward the viewer. To create this image, the receptor was labelled with a radioligand (radioactively labelled chemical that binds to a protein of interest) to enable its detection. 5 individual PET images were taken and then rendered in 3D to give the unique signature set of structures seen here. These include the amygdala, ventral striatum, the anterior cingulate gyrus, the hippocampi on both sides of the brain and parts of the temporal lobe. The function of various parts of the limbic system is to regulate impulsivity and response to emotions, such as fear and desire. Visualising neurotransmitters and their receptors gives a unique functional perspective on the brain and allows correlation of function with structures and networks within the brain. This is at the forefront of neuroscientific research in living humans. Horizontal width of image is approximately 20 cm.
