2014年4月8日火曜日

Cue-Induced Craving Increases Impulsivity via Changes in Striatal Value Signals in Problem Gamblers

Stephan F. Miedl, Christian Buchel, and Jan Peters
J. Neurosci. 2014;34 4750-4755

ギャンブル中毒者は「ギャンブルを連想させる画像」を見ると、時間割引率が高くなる(衝動的になる=直近の報酬を高く評価する)。
また、その際には、中脳と腹側線条体における「価値」の表現方法が(ギャンブルを連想させない画像を見た際とは)異なっている。

Impulsive behavior such as steep temporal discounting is a hallmark of addiction and is associated with relapse. In pathological gamblers, discounting may be further increased by the presence of gambling-related cues in the environment, but the extent to which the gambling relatedness of task settings affects reward responses in gambling addiction is debated. In the present study, human problem gamblers made choices between immediate rewards and individually tailored larger-but-later rewards while visual gambling-related scenes were presented in the background. N = 17 participants were scanned using fMRI, whereas N = 5 additional participants completed a behavioral version of the task. Postscan craving ratings were acquired for each image, and behavioral and neuroimaging data were analyzed separately for high- and low-craving trials (median split analysis). Discounting was steeper for high versus low craving trials. Neuroimaging revealed a positive correlation with model-based subjective value in midbrain and striatum in low-craving trials that was reversed in high-craving trials. These findings reveal a modulation of striatal reward responses in gamblers by addiction-related cues, and highlight a potentially important mechanism that may contribute to relapse. Cue-induced changes in striatal delayed reward signals may lead to increased discounting of future rewards, which might in turn affect the likelihood of relapse.

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