Department of Psychology and Brain Research Center, University of British Columbia, 2136 West Mall, Vancouver, BC, V6T 1Z4, Canada.
Psychopharmacology (Berl). 2010 Aug;211(2):209-21. doi: 10.1007/s00213-010-1883-y. Epub 2010 May 22.
Evaluation of risks and rewards associated with different options is facilitated by components of the mesocorticolimbic dopamine (DA) system. Augmenting or reducing DA activity increases or decreases preference for larger, uncertain rewards when reward probabilities decrease within a session. However, manipulations of DA activity may differentially alter risky choice when shifts in the relative value of probabilistic rewards are greater or lesser than those experienced previously.
We investigated the effects of amphetamine and the DA antagonist flupenthixol on risk discounting, whereby we altered the manner in which reward probabilities changed.
Rats chose between a "Small/Certain" (one pellet) and a "Large/Risky" lever that delivered four pellets in a probabilistic manner that changed during a session. Separate groups of rats were trained with a descending (100%, 50%, 25%, 12.5%), ascending (12.5-100%) or mixed (100%, 12.5%, 25%, 50%) order of probabilities associated with the large/risky option.
Flupenthixol consistently decreased preference for the large/risky option. In contrast, amphetamine increased preference for the large/risky lever when the probabilities decreased over a session, but reduced preference in the ascending condition.
Reductions in normal DA tone consistently biases choice away larger, probabilistic rewards. In contrast, increases in DA release may disrupt adjustments in behavior in response to changes in the relative value of certain versus uncertain rewards. These findings further clarify the role of DA in mediating risk/reward judgments and how perturbations in DA signaling may interfere with the ability to adjust decision making in response to changes in reward contingencies.
中脑边缘多巴胺(DA)系统的组成部分有助于评估不同选择的风险和回报。当在一个会话中奖励概率降低时,增加或减少 DA 活动会增加或减少对更大、不确定奖励的偏好。然而,当概率奖励的相对价值变化大于或小于之前经历的变化时,DA 活动的操纵可能会对风险选择产生不同的影响。
我们研究了安非他命和 DA 拮抗剂氟哌噻吨对风险贴现的影响,即我们改变了奖励概率变化的方式。
大鼠在“小/确定”(一个小球)和“大/风险”杠杆之间进行选择,以概率方式提供四个小球,在一个会话中变化。分别用下降(100%、50%、25%、12.5%)、上升(12.5-100%)或混合(100%、12.5%、25%、50%)顺序训练大鼠与大/风险选项相关的概率。
氟哌噻吨一致降低了对大/风险选项的偏好。相比之下,当概率在一个会话中下降时,安非他命增加了对大/风险杠杆的偏好,但在上升条件下降低了偏好。
正常 DA 张力的降低始终使选择偏向于更大的、概率性奖励。相比之下,DA 释放的增加可能会破坏对确定与不确定奖励的相对价值变化的行为调整。这些发现进一步阐明了 DA 在调节风险/回报判断中的作用,以及 DA 信号的干扰如何干扰根据奖励条件的变化调整决策的能力。