McBride Dharma, Barrett Sean P, Kelly Jared T, Aw Andrew, Dagher Alain
McConnell Brain Imaging Center, Montreal Neurological Institute, McGill University, Montreal, QC, Canada.
Neuropsychopharmacology. 2006 Dec;31(12):2728-38. doi: 10.1038/sj.npp.1301075. Epub 2006 Apr 5.
Cues associated with drug taking can trigger relapse, drug seeking, and craving in addicted individuals. Behavioral studies suggest that drug availability and withdrawal can affect the individual response to drug cues. Moreover, the importance of subjective craving in cue-induced relapse has been questioned and an alternative model put forward according to which drug cues trigger habitual drug-seeking behaviors independently of craving. We used functional magnetic resonance imaging to compare the brain response to smoking and control videotapes in 20 healthy smokers, while varying their expectancy to smoke and abstinence levels. The neural response to cigarette cues was strongly modulated by expectancy and, to a lesser extent, abstinence. In people expecting to smoke immediately after the scan, smoking cues activated brain areas implicated in arousal, attention, and cognitive control. However, when subjects knew they would not be allowed to smoke for 4 h, there was almost no brain activation in response to smoking cues, despite equivalent reported levels of craving. In the dorsolateral prefrontal cortex, the neural response was a function of both craving and expectancy. Thalamo-cingulate connectivity, thought to be an index of arousal, was greater during expectancy than nonexpectancy. Our findings confirm the importance of expectancy in the neural response to drug cues, and lend support to the theory that these cues act on brain areas involved in arousal and attention.
与吸毒相关的线索可引发成瘾个体的复吸、觅药行为和渴求。行为学研究表明，药物可得性和戒断会影响个体对药物线索的反应。此外，主观渴求在线索诱导的复吸中的重要性受到质疑，有人提出了一种替代模型，即药物线索独立于渴求触发习惯性觅药行为。我们使用功能磁共振成像比较了20名健康吸烟者对吸烟和对照录像带的大脑反应，同时改变他们的吸烟预期和戒断水平。对香烟线索的神经反应受到预期的强烈调节，在较小程度上也受到戒断的调节。在扫描后立即预期吸烟的人群中，吸烟线索激活了与唤醒、注意力和认知控制相关的脑区。然而，当受试者知道他们在4小时内不被允许吸烟时，尽管报告的渴求水平相当，但对吸烟线索几乎没有脑激活反应。在背外侧前额叶皮层，神经反应是渴求与预期两者的函数。丘脑-扣带回连接被认为是唤醒的指标，在预期期间比非预期期间更强。我们的研究结果证实了预期在对药物线索的神经反应中的重要性，并支持了这些线索作用于参与唤醒和注意力的脑区这一理论。
