Effects of lesions of the nucleus accumbens core on choice between small certain rewards and large uncertain rewards in rats.
Effects of lesions of the nucleus accumbens core on choice between small certain rewards and large uncertain rewards in rats.
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DOI：
10.1186/1471-2202-6-37
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发表时间：
2005-05-28
期刊：
影响因子：
2.4
通讯作者：
Howes, NJ
中科院分区：
文献类型：
--
作者：
Cardinal, RN;Howes, NJ
动物必须经常在各种行动方案之间做出选择，寻求获得最大利益。因此，他们必须评估现有结果的规模和可能性。我们对这一过程的神经基础知之甚少，也不知道是什么使个体倾向于过度保守或过度冒险（分别是避免或偏好不确定性）。已知丘脑核核心（AcbC）有助于大鼠选择大的、延迟的奖励而不是小的、立即的奖励的能力; AcbC病变导致冲动选择和延迟强化的学习障碍。然而，目前尚不清楚AcbC如何有助于涉及概率强化的选择，例如在大的，不确定的奖励和小的，确定的奖励之间。我们研究了大鼠AcbC的兴奋性毒性病变对概率选择的影响。在离散试验任务中，大鼠在确定性（p = 1）的单个食物颗粒和具有不同程度不确定性（p = 1，0.5，0.25，0.125和0.0625）的四个食物颗粒之间进行选择，在整个过程中，大概率降低或增加。受试者接受这项任务的训练，然后在重新测试之前接受AcbC的兴奋性毒性或假损伤。在短暂的一段时间内，与对照组相比，AcbC损伤的大鼠表现出两种选择之间的相对差异，AcbC损伤的大鼠表现出风险厌恶的选择，当不确定时，选择大的食物的频率低于对照组，以至于它们获得的食物较少。到试验结束时，大鼠表现为在p = 0.32（假手术）或p = 0.70（AcbC损伤）时，在单个特定颗粒和四个颗粒之间无差异。当概率在整个过程中没有变化时，AcbC损伤的大鼠和对照组在确定时强烈偏好大肿瘤，并且在大肿瘤不太可能发生时强烈偏好小肿瘤（p = 0.0625），AcbC损伤组和假手术组之间没有差异。这些结果支持了这样的观点，即AcbC有助于行动选择，促进选择的不确定性，以及延迟，强化。
Animals must frequently make choices between alternative courses of action, seeking to maximize the benefit obtained. They must therefore evaluate the magnitude and the likelihood of the available outcomes. Little is known of the neural basis of this process, or what might predispose individuals to be overly conservative or to take risks excessively (avoiding or preferring uncertainty, respectively). The nucleus accumbens core (AcbC) is known to contribute to rats' ability to choose large, delayed rewards over small, immediate rewards; AcbC lesions cause impulsive choice and an impairment in learning with delayed reinforcement. However, it is not known how the AcbC contributes to choice involving probabilistic reinforcement, such as between a large, uncertain reward and a small, certain reward. We examined the effects of excitotoxic lesions of the AcbC on probabilistic choice in rats. Rats chose between a single food pellet delivered with certainty (p = 1) and four food pellets delivered with varying degrees of uncertainty (p = 1, 0.5, 0.25, 0.125, and 0.0625) in a discrete-trial task, with the large-reinforcer probability decreasing or increasing across the session. Subjects were trained on this task and then received excitotoxic or sham lesions of the AcbC before being retested. After a transient period during which AcbC-lesioned rats exhibited relative indifference between the two alternatives compared to controls, AcbC-lesioned rats came to exhibit risk-averse choice, choosing the large reinforcer less often than controls when it was uncertain, to the extent that they obtained less food as a result. Rats behaved as if indifferent between a single certain pellet and four pellets at p = 0.32 (sham-operated) or at p = 0.70 (AcbC-lesioned) by the end of testing. When the probabilities did not vary across the session, AcbC-lesioned rats and controls strongly preferred the large reinforcer when it was certain, and strongly preferred the small reinforcer when the large reinforcer was very unlikely (p = 0.0625), with no differences between AcbC-lesioned and sham-operated groups. These results support the view that the AcbC contributes to action selection by promoting the choice of uncertain, as well as delayed, reinforcement.
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