Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109
Department of Neurosurgery, University of California Los Angeles, Los Angeles, California 90025.
J Neurosci. 2020 Nov 11;40(46):8951-8963. doi: 10.1523/JNEUROSCI.2947-19.2020. Epub 2020 Oct 12.
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. 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，多巴胺系统参与了对奖励预测线索的动机价值的归因，以及对预测误差的归因。为了评估这一点，从执行包含具有“预测”和“激励”属性的线索的巴甫洛夫接近任务的雄性大鼠中记录多巴胺神经元。所有动物都学会了线索的预测性质（照亮的杠杆进入笼子），但有些动物也发现线索具有吸引力，并被激励去接近它（“标志追踪者”，STs）。“目标追踪者”（GTs）主要接近奖励接受器的位置。大鼠被植入四极管，以便在腹侧被盖区进行神经电生理记录。细胞的特征是尖峰波形形状和放电率。评估了与巴甫洛夫行为、线索呈现和奖励传递有关的放电率和反应幅度。我们鉴定了 103 个多巴胺和 141 个非多巴胺神经元。GTs 和 STs 都对初始杠杆呈现（CS1）和杠杆缩回（CS2）有反应。然而，只有 STs 在杠杆相互作用期间维持更高的放电率。此外，STs 的多巴胺细胞对 CS1 和 CS2 的反应比例明显更高。这些是第一个表明 VTA 神经元编码预测和激励线索的结果，支持多巴胺神经元在将激励显著性归因于与奖励相关的线索方面的重要作用，并强调了个体之间潜在的动机行为差异的后果。这个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著性的差异。VTA 的神经元如何影响 NAcc 的信号传递以及随后的多巴胺释放仍然知之甚少。所有在奖励之前出现的线索在本质上都是预测性的。然而，有些线索也具有激励价值，因为它们引起接近它们的行为。我们通过线索接近行为和线索相互作用以及相应的 VTA 神经放电幅度来量化激励显著性的归因。我们发现 VTA 的多巴胺神经元编码奖励线索激励显著性的强度。这表明多巴胺神经元专门在 VTA 中编码动机。
