It has been argued that the dopaminergic system is involved in the attribution of motivational value to reward predictive cues as well as prediction error. To evaluate, dopamine neurons were recorded from male rats performing a Pavlovian approach task containing cues that have both "predictive" and "incentive" properties. All animals learned the predictive nature of the cue (illuminated lever entry into cage), but some also found the cue to be attractive and were motivated toward it ("sign-trackers," STs). "Goal-trackers" (GTs) predominantly approached the location of reward receptacle. Rats were implanted with tetrodes for neural electrophysiological recordings in the ventral tegmental area. Cells were characterized by spike waveform shape and firing rate. Firing rates and magnitudes of responses in relation to Pavlovian behaviors, cue presentation, and reward delivery were assessed. We identified 103 dopamine and 141 nondopamine neurons. GTs and STs both showed responses to the initial lever presentation (CS1) and lever retraction (CS2). However, higher firing rates were sustained during the lever interaction period only in STs. Further, dopamine cells of STs showed a significantly higher proportion of cells responding to both CS1 and CS2. These are the first results to show that neurons from the VTA encode both predictive and incentive cues, support an important role for dopamine neurons in the attribution of incentive salience to reward-paired cues, and underscore the consequences of potential differences in motivational behavior between individuals.

SIGNIFICANCE STATEMENT This project serves to determine whether dopamine neurons encode differences in cued approach behaviors and incentive salience. How neurons of the VTA affect signaling through the NAcc and subsequent dopamine release is still not well known. All cues that precede a reward are predictive in nature. Some, however, also have incentive value, in that they elicit approach toward them. We quantified the attribution of incentive salience through cue approach behavior and cue interaction, and the corresponding magnitude of VTA neural firing. We found dopamine neurons of the VTA encode strength of incentive salience of reward cues. This suggests that dopamine neurons specifically in the VTA encode motivation.

有人认为，多巴胺能系统参与奖励预测线索和预测错误的动机价值的归因。为了进行评估，记录了执行巴甫洛夫方法任务的雄性大鼠的多巴胺神经元，其中包含具有“预测”和“激励”特性的线索。所有动物都了解了提示的预测性质（带照明的杠杆进入笼子），但有些动物也发现提示很有吸引力并受到激励（“信号跟踪器”，ST）。 “目标追踪器”（GT）主要接近奖励容器的位置。大鼠被植入四极管，用于腹侧被盖区的神经电生理记录。细胞的特征在于尖峰波形形状和放电率。评估了与巴甫洛夫行为、提示呈现和奖励传递相关的放电率和反应幅度。我们鉴定出 103 个多巴胺神经元和 141 个非多巴胺神经元。 GT 和 ST 均表现出对初始杠杆呈现 (CS1) 和杠杆缩回 (CS2) 的反应。然而，只有 ST 在杠杆相互作用期间维持了较高的发射率。此外，ST 的多巴胺细胞显示出对 CS1 和 CS2 均做出反应的细胞比例显着更高。这些是第一个结果，表明 VTA 神经元编码预测和激励线索，支持多巴胺神经元在奖励配对线索的激励显着性归因中发挥重要作用，并强调个体之间动机行为潜在差异的后果。

意义声明该项目旨在确定多巴胺神经元是否编码提示接近行为和激励显着性的差异。 VTA 神经元如何影响 NAcc 的信号传导以及随后的多巴胺释放仍不清楚。奖励之前的所有线索本质上都是预测性的。然而，有些也具有激励价值，因为它们会引起人们对它们的接近。我们通过线索接近行为和线索交互来量化激励显着性的归因，以及 VTA 神经放电的相应幅度。我们发现 VTA 的多巴胺神经元编码奖励线索的激励显着性强度。这表明，VTA 中的多巴胺神经元专门编码动机。