Hariri Ahmad R, Brown Sarah M, Williamson Douglas E, Flory Janine D, de Wit Harriet, Manuck Stephen B
Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
J Neurosci. 2006 Dec 20;26(51):13213-7. doi: 10.1523/JNEUROSCI.3446-06.2006.
Discounting future outcomes as a function of their deferred availability underlies much of human decision making. Discounting, or preference for immediate over delayed rewards of larger value, is often associated with impulsivity and is a risk factor for addictive disorders such as pathological gambling, cigarette smoking, and drug and alcohol abuse. The ventral striatum (VS) is involved in mediating behavioral responses and physiological states associated with reward, and dysregulation of the VS contributes to addiction, perhaps by affecting impulsive decision-making. Behavioral tests of delay discounting (DD), which index preference for smaller immediate over larger delayed rewards, covary with impulsive tendencies in humans. In the current study, we examined the relationship between individual differences in DD, measured in a behavioral assessment, and VS activity measured with blood oxygenation level-dependent functional magnetic resonance imaging, in 45 adult volunteers. VS activity was determined using a task involving positive and negative feedback with monetary reward. Analyses revealed that individual differences in DD correlate positively with magnitude of VS activation in response to both positive and negative feedback, compared with a no-feedback control condition. Variability in DD was also associated with differential VS activation in response to positive, compared with negative, feedback. Collectively, our results suggest that increased preference for smaller immediate over larger delayed rewards reflects both a relatively indiscriminate and hyper-reactive VS circuitry. They also highlight a specific neurocognitive mechanism that may contribute to increased risk for addiction.
将未来结果按照其延迟可得性进行折扣是人类决策的重要基础。折扣，即对即时奖励而非更大价值的延迟奖励的偏好，通常与冲动性相关，并且是诸如病态赌博、吸烟以及药物和酒精滥用等成瘾性障碍的一个风险因素。腹侧纹状体（VS）参与介导与奖励相关的行为反应和生理状态，并且VS的功能失调可能通过影响冲动决策而导致成瘾。延迟折扣（DD）的行为测试，即衡量对较小即时奖励而非较大延迟奖励的偏好，与人类的冲动倾向相关。在本研究中，我们在45名成年志愿者中，考察了通过行为评估测量的DD个体差异与通过血氧水平依赖性功能磁共振成像测量的VS活动之间的关系。VS活动通过一项涉及金钱奖励的正反馈和负反馈任务来确定。分析表明，与无反馈对照条件相比，DD的个体差异与对正反馈和负反馈的VS激活幅度呈正相关。DD的变异性也与对正反馈而非负反馈的VS激活差异有关。总体而言，我们的结果表明，相较于更大的延迟奖励，对较小即时奖励的偏好增加反映了VS回路相对不加区分且反应过度。它们还突出了一种可能导致成瘾风险增加的特定神经认知机制。
