Neurosciences Institute and Department of Biology, University of Texas at San Antonio, San Antonio, TX 78249.
Neurosciences Institute and Department of Biology, University of Texas at San Antonio, San Antonio, TX 78249
Proc Natl Acad Sci U S A. 2019 Jul 2;116(27):13641-13650. doi: 10.1073/pnas.1904249116. Epub 2019 Jun 17.
Learning to avoid aversive outcomes is an adaptive strategy to limit one's future exposure to stressful events. However, there is considerable variance in active avoidance learning across a population. The mesolimbic dopamine system contributes to behaviors elicited by aversive stimuli, although it is unclear if the heterogeneity in active avoidance learning is explained by differences in dopamine transmission. Furthermore, it is not known how dopamine signals evolve throughout active avoidance learning. To address these questions, we performed voltammetry recordings of dopamine release in the ventral medial striatum throughout training on inescapable footshock and signaled active avoidance tasks. This approach revealed differences in the pattern of dopamine signaling during the aversive cue and the safety period that corresponded to subsequent task performance. Dopamine transmission throughout the footshock bout did not predict performance but rather was modulated by the prior stress exposure. Additionally, we demonstrate that dopamine encodes a safety prediction error signal, which illustrates that ventral medial striatal dopamine release conveys a learning signal during both appetitive and aversive conditions.
学会避免不愉快的结果是一种适应性策略，可以限制一个人未来接触压力事件的次数。然而，在整个人群中，主动回避学习存在相当大的差异。中脑边缘多巴胺系统有助于对厌恶刺激引发的行为，但尚不清楚主动回避学习的异质性是否可以用多巴胺传递的差异来解释。此外，目前尚不清楚多巴胺信号在主动回避学习过程中是如何演变的。为了解决这些问题，我们在不可逃避的足底电击和信号主动回避任务训练过程中，对腹内侧纹状体中的多巴胺释放进行了伏安法记录。这种方法揭示了在厌恶线索和安全期间多巴胺信号的模式差异，这与随后的任务表现相对应。整个电击过程中的多巴胺传递并不能预测表现，而是受到先前应激暴露的调节。此外，我们证明多巴胺编码了一个安全预测误差信号，这表明腹内侧纹状体中的多巴胺释放在奖赏和厌恶条件下都传递了一个学习信号。
