The enhanced sensitivity of the motivational circuitry to drugs in addicted subjects is exemplified by a study by Volkow et al. (72): Whereas cocaine-addicted subjects exposed to a stimulant drug showed increased metabolism in the ventral ACC and medial orbitofrontal cortex (an effect that was associated with craving for the administered drug), nonaddicted subjects exposed to the same drug had decreased metabolism in these regions. This suggests that activation of these prefrontal regions with drug exposure may be specific to addiction and associated with the enhanced desire for the drug.
