Long-term exposure to
drug may alter the
neural system associated with affective processing, as evidenced by both clinical observations and behavioral data documenting dysfunctions in
emotional experiences and processing in
drug addicts. Although many
imaging studies examined
neural responses to
drug or drug-related cues in addicts, there have been few studies explicitly designed to reveal their
neural abnormalities in processing non-drug-related natural affective materials. The present study asked
abstinent heroin addicts and normal controls to passively view standardized affective pictures of positive, negative, or neutral valence and compared their
brain activities with functional
MRI. Compared to normal controls, addicts showed reduced
activation in right
amygdala in response to the affective pictures, consistent with previous reports of blunted subjective experience for affective stimuli in addicts. Furthermore, in two
visual cortical areas BA 19 and 37, while the controls showed greater responses to positive pictures than to negative ones replicating literature findings, the addicts showed the opposite pattern. The results reveal a complex pattern of altered processing of non-drug-related affective materials in addicts showing both heightened and blunted
neural responses in different
brain regions and for different stimulus valence. The present study highlights the importance of
brain imaging research on
drug addicts' processing of affective stimuli in understanding disruptions in their
emotion circuitry.
