Nucleus accumbens core lesions retard instrumental learning and performance with delayed reinforcement in the rat.
Nucleus accumbens core lesions retard instrumental learning and performance with delayed reinforcement in the rat.
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DOI：
10.1186/1471-2202-6-9
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发表时间：
2005-02-03
期刊：
影响因子：
2.4
通讯作者：
Cheung TH
中科院分区：
文献类型：
--
作者：
Cardinal RN;Cheung TH
行动和结果之间的延迟严重阻碍了强化学习系统，但人们对动物克服这个问题并弥合这种延迟的神经机制知之甚少。大鼠腹侧纹状体的一部分--丘脑核核心（AcbC）是大鼠对大的、延迟的奖励（自我控制的选择）的正常偏好所必需的，但其原因尚不清楚。我们研究了AcbC在学习自由操作工具响应使用延迟强化的作用，延迟强化的先前学习的响应的性能，以及两种不同奖励的相对大小的评估。组大鼠兴奋性或假病变的AcbC获得了不同的延迟（0，10，或20秒）之间的压力响应和delivery的仪器响应。第二个（不活动的）杠杆也存在，但对它的反应从未得到加强。正如预期的那样，这种延迟阻碍了正常大鼠的学习。AcbC病变并不妨碍学习的情况下，延迟，但AcbC损伤的大鼠在学习受损时，有一个延迟，相对于假手术对照。所有的组最终获得的反应，并区分活动杠杆从非活动杠杆在一定程度上。随后训练大鼠辨别不同大小的干扰物。AcbC损伤的大鼠比假手术对照组更敏感的差异，更大的幅度，这表明在自我控制的选择赤字以前观察到的大鼠是一个结果，减少偏好延迟奖励相对于立即奖励，而不是减少偏好大奖励相对于小奖励。AcbC病变也损害了以前学习的仪器响应的延迟依赖性方式的性能。这些结果表明，AcbC有助于工具性学习和性能之间的桥梁主体的行动和随后的结果，加强行为的延迟。
Delays between actions and their outcomes severely hinder reinforcement learning systems, but little is known of the neural mechanism by which animals overcome this problem and bridge such delays. The nucleus accumbens core (AcbC), part of the ventral striatum, is required for normal preference for a large, delayed reward over a small, immediate reward (self-controlled choice) in rats, but the reason for this is unclear. We investigated the role of the AcbC in learning a free-operant instrumental response using delayed reinforcement, performance of a previously-learned response for delayed reinforcement, and assessment of the relative magnitudes of two different rewards. Groups of rats with excitotoxic or sham lesions of the AcbC acquired an instrumental response with different delays (0, 10, or 20 s) between the lever-press response and reinforcer delivery. A second (inactive) lever was also present, but responding on it was never reinforced. As expected, the delays retarded learning in normal rats. AcbC lesions did not hinder learning in the absence of delays, but AcbC-lesioned rats were impaired in learning when there was a delay, relative to sham-operated controls. All groups eventually acquired the response and discriminated the active lever from the inactive lever to some degree. Rats were subsequently trained to discriminate reinforcers of different magnitudes. AcbC-lesioned rats were more sensitive to differences in reinforcer magnitude than sham-operated controls, suggesting that the deficit in self-controlled choice previously observed in such rats was a consequence of reduced preference for delayed rewards relative to immediate rewards, not of reduced preference for large rewards relative to small rewards. AcbC lesions also impaired the performance of a previously-learned instrumental response in a delay-dependent fashion. These results demonstrate that the AcbC contributes to instrumental learning and performance by bridging delays between subjects' actions and the ensuing outcomes that reinforce behaviour.
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