Is heroin addiction related to a dysfunctional processing of reward and hedonism in the brain? Insights from neuroimaging studies

The functioning of reward in drug addicts is a major issue both in terms of pathophysiology and in a rehabilitative view. We used a PET imaging device to assess the hedonic functioning of methadone maintained heroin addicts, compared to control subjects, by two modalities: 1) the elicitation of interest by anticipated monetary reward; 2) the neuroimaging correlates of visually elicited pleasure. In heroin addicts fewer brain regions showed activated during tasks implying known monetary reward in comparison to tasks without any reward. On the other hand, the processing of subjectively pleasant videoclips resorted to different brain pathways in heroin addicts. Heroin addicts seem to show a lower level of anticipatory sensitivity to monetary reward, whereas the topography of pleasure-feeling seems to be different from normal subjects’. Such results show a different reward-seeking and reward-feeling status of methadone maintained heroin addicts, although it is to be clarified whether such a status was also forerunning heroin use, or developed as a correlate of addiction.