Chronic effects of cannabis use on the human reward system: an fMRI study.
ABSTRACT Cannabis is one of the most used drugs of abuse. It affects the brain reward system in animals, and has proven rewarding and addictive potential in humans. We used functional MRI to measure brain activity during reward anticipation in a monetary reward task. Long-term cannabis users were compared to healthy controls. An additional control group consisting of nicotine users was included. Cannabis users showed attenuated brain activity during reward anticipation in the nucleus accumbens compared to non-smoking controls, but not compared to smoking controls. Cannabis users showed decreased reward anticipation activity in the caudate nucleus, compared to both non-smoking and smoking controls. These data suggest that nicotine may be responsible for attenuated reward anticipation activity in the accumbens, but that differences in the caudate are associated with the use of cannabis. Our findings imply that chronic cannabis use as well as nicotine, may cause an altered brain response to rewarding stimuli.
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ABSTRACT: Reward cues have been found to increase the investment of effort in tasks even when cues are presented suboptimally (i.e. very briefly), making them hard to con-sciously detect. Such effort responses to suboptimal reward cues are assumed to rely mainly on the mesolimbic dopa-mine system, including the ventral striatum. To provide further support for this assumption, we performed two studies investigating whether these effort responses vary with individual differences in markers of striatal dopami-nergic functioning. Study 1 investigated the relation between physical effort responses and resting state eye-blink rate. Study 2 examined cognitive effort responses in relation to individually averaged error-related negativity. In both stud-ies effort responses correlated with the markers only for suboptimal, but not for optimal reward cues. These findings provide further support for the idea that effort responses to suboptimal reward cues are mainly linked to the mesolimbic dopamine system, while responses to optimal reward cues also depend on higher-level cortical functions.Motivation and Emotion 09/2014; 38(6). DOI:10.1007/s11031-014-9434-1 · 1.55 Impact Factor
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ABSTRACT: The premenstrual phase of the menstrual cycle is associated with marked changes in normal and abnormal motivated behaviors. Animal studies suggest that such effects may result from actions of gonadal hormones on the mesolimbic dopamine (DA) system. We therefore investigated premenstrual changes in reward-related neural activity in terminal regions of the DA system in humans. Twenty-eight healthy young women underwent functional magnetic resonance imaging on 2 days during the menstrual cycle, once during the late follicular phase and once during the premenstrual phase, in counterbalanced order. Using a modified version of the monetary incentive delay task, we assessed responsiveness of the ventral striatum to reward anticipation. Our results show enhanced ventral striatal responses during the premenstrual as compared to the follicular phase. Moreover, this effect was most pronounced in women reporting more premenstrual symptoms. These findings provide support for the notion that changes in functioning of mesolimbic incentive processing circuits may underlie premenstrual changes in motivated behaviors. Notably, increases in reward-cue responsiveness have previously been associated with DA withdrawal states. Our findings therefore suggest that the sharp decline of gonadal hormone levels in the premenstrual phase may trigger a similar withdrawal-like state.Social Cognitive and Affective Neuroscience 10/2011; 6(5):612-20. DOI:10.1093/scan/nsq071 · 5.88 Impact Factor
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ABSTRACT: Disturbed reward processing in humans has been associated with a number of disorders, such as depression, addiction, and attention-deficit hyperactivity disorder. The endocannabinoid (eCB) system has been implicated in reward processing in animals, but in humans, the relation between eCB functioning and reward is less clear. The current study uses functional magnetic resonance imaging (fMRI) to investigate the role of the eCB system in reward processing in humans by examining the effect of the eCB agonist Δ(9)-tetrahydrocannabinol (THC) on reward-related brain activity. Eleven healthy males participated in a randomized placebo-controlled pharmacological fMRI study with administration of THC to challenge the eCB system. We compared anticipatory and feedback-related brain activity after placebo and THC, using a monetary incentive delay task. In this task, subjects are notified before each trial whether a correct response is rewarded ("reward trial") or not ("neutral trial"). Subjects showed faster reaction times during reward trials compared to neutral trials, and this effect was not altered by THC. THC induced a widespread attenuation of the brain response to feedback in reward trials but not in neutral trials. Anticipatory brain activity was not affected. These results suggest a role for the eCB system in the appreciation of rewards. The involvement of the eCB system in feedback processing may be relevant for disorders in which appreciation of natural rewards may be affected such as addiction.Psychopharmacology 08/2011; 219(4):981-90. DOI:10.1007/s00213-011-2428-8 · 3.99 Impact Factor