Brain imaging studies in human addicts.

Addiction provides fertile ground for the application of the tools of functional neuroimaging. They can be divided into studies of neural activity and neurotransmitter function. Using the former, both opiates and stimulants cause a global decrease in brain metabolism. Against this background, acute doses have still been shown to produce relative increases in brain activation in specific regions, e.g., anterior cingulate, thalamus, and amygdala. These are also regions frequently found with cue-exposure paradigms. Our own work on cue-exposure has shown that heroin-related stimuli provoke activation of the anterior cingulate and orbitofrontal regions. Brain metabolism has also been shown to increase in drug withdrawal from alcohol and cocaine. Neurotransmitter studies have shown that in alcohol dependence, GABA(A)-benzodiazepine (GABA-BDZ) receptors are reduced in a number of brain regions and suggest that there may be 'capacity within the system' in some benzodiazepine functions, but tolerance to others, e.g., time asleep. Finally, 11C-Ro15-4513 offers new opportunities for imaging the GABA-BDZ system.