The nucleus accumbens core (NAc) is important for integrating and providing information to downstream areas about the timing and value of anticipated reward. Although NAc is one of the first brain regions to be affected by drugs of abuse, we still do not know how neural correlates related to reward expectancy are affected by previous cocaine self-administration. To address this issue, we recorded from single neurons in the NAc of rats that had previously self-administered cocaine or sucrose (control). Neural recordings were then taken while rats performed an odor-guided decision-making task in which we independently manipulated value of expected reward by changing the delay to or size of reward across a series of trial blocks. We found that previous cocaine self-administration made rats more impulsive, biasing choice behavior toward more immediate reward. Further, compared to controls, cocaine-exposed rats showed significantly fewer neurons in the NAc that were responsive during odor cues and reward delivery, and in the reward-responsive neurons that remained, diminished directional and value encoding was observed. Lastly, we found that after cocaine exposure, reward-related firing during longer delays was reduced compared to controls. These results demonstrate that prior cocaine self-administration alters reward-expectancy encoding in NAc, which could contribute to poor decision making observed after chronic cocaine use.

中文翻译：

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先前的可卡因自我给药会破坏腹侧纹状体的奖赏预期编码。


伏隔核核心（NAc）对于整合并向下游区域提供有关预期奖励的时间和价值的信息非常重要。尽管 NAc 是最先受到滥用药物影响的大脑区域之一，但我们仍然不知道与奖赏预期相关的神经相关性如何受到先前可卡因自我给药的影响。为了解决这个问题，我们记录了先前自行注射可卡因或蔗糖（对照）的大鼠 NAc 中的单个神经元。然后，在大鼠执行气味引导决策任务时进行神经记录，在该任务中，我们通过改变一系列试验块中奖励的延迟或大小来独立操纵预期奖励的值。我们发现，先前的可卡因自我给药使老鼠更加冲动，使选择行为偏向于更直接的奖励。此外，与对照组相比，暴露于可卡因的大鼠的 NAc 中对气味提示和奖励传递有反应的神经元显着减少，并且在剩余的奖励反应神经元中，观察到方向和价值编码减少。最后，我们发现接触可卡因后，与对照组相比，较长延迟期间与奖励相关的放电减少了。这些结果表明，先前的可卡因自我给药改变了 NAc 中的奖赏预期编码，这可能导致长期使用可卡因后观察到的不良决策。