Munkhzaya Unur, Chinzorig Choijiljav, Matsumoto Jumpei, Nishimaru Hiroshi, Ono Taketoshi, Nishijo Hisao
System Emotional Science, Faculty of Medicine, University of Toyama, Toyama, Japan.
Department of Physiology, School of Bio-Medicine, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
Front Behav Neurosci. 2020 Sep 9;14:565002. doi: 10.3389/fnbeh.2020.565002. eCollection 2020.
The paraventricular nucleus of the thalamus (PVT) has been implicated in cue-induced motivated behaviors. Although reward-associated cues (conditioned stimuli, CSs) contain different types of information including predictive information of future reward delivery and incentive (motivational) value of the reward, it remains unknown whether PVT neurons represent predictive and incentive information of CSs. It is suggested that neural activity just after the onset of CSs (early activity) and that just before reward delivery (late activity) might more strongly represent predictive and incentive information, respectively. In this study, rats were trained to lick a tube, which was protruded close to their mouth just after a CS, to obtain a reward (sucrose or water) (cue-induced licking task). Auditory and visual CSs were used: each elemental cue (CS) predicted reward or non-reward outcome, while simultaneous presentation of the two elemental cues (configural cues) predicted the opposite reward outcome. We recorded PVT neurons in the cue-induced licking task, and report that half of the CS-responsive PVT neurons responded selectively to the CSs predicting reward outcome regardless of physical property of the cues (CS-selective). In addition, the early activity of the CS-selective neurons discriminated reward/non-reward association (predictive information) and was less sensitive to reward value and motivation reflected by lick latency (incentive information), while the late activity of the CS-selective neurons was correlated with reward value and motivation rather than reward/non-reward association. Early and late population activity of the CS-selective neurons also represented predictive and incentive information of the CSs, respectively. On the other hand, activity of more than half of the PVT neurons was correlated with individual licking during licking to acquire reward. Taken together, the results suggest that the PVT neurons engage in different neural processes involved in cue-induced motivated behaviors: CS encoding to determine reward availability and form motivation for reward-seeking behavior, and hedonic mouth movements during reward consumption.
丘脑室旁核（PVT）与线索诱导的动机行为有关。尽管与奖励相关的线索（条件刺激，CSs）包含不同类型的信息，包括未来奖励发放的预测信息和奖励的激励（动机）价值，但PVT神经元是否代表CSs的预测和激励信息仍不清楚。有人认为，CSs开始后不久的神经活动（早期活动）和奖励发放前的神经活动（晚期活动）可能分别更强烈地代表预测和激励信息。在本研究中，训练大鼠舔舐一根在CSs出现后靠近其嘴部伸出的管子以获得奖励（蔗糖或水）（线索诱导舔舐任务）。使用了听觉和视觉CSs：每个基本线索（CS）预测奖励或无奖励结果，而两个基本线索同时呈现（构型线索）预测相反的奖励结果。我们在线索诱导舔舐任务中记录了PVT神经元，并报告说，一半的CS反应性PVT神经元对预测奖励结果的CSs有选择性反应，而不管线索的物理特性如何（CS选择性）。此外，CS选择性神经元的早期活动区分奖励/无奖励关联（预测信息），并且对舔舐潜伏期所反映的奖励价值和动机（激励信息）不太敏感，而CS选择性神经元的晚期活动与奖励价值和动机相关，而不是与奖励/无奖励关联相关。CS选择性神经元的早期和晚期群体活动也分别代表了CSs的预测和激励信息。另一方面，超过一半的PVT神经元的活动与获取奖励时的个体舔舐行为相关。综上所述，结果表明PVT神经元参与了线索诱导的动机行为中不同的神经过程：CS编码以确定奖励可用性并形成寻求奖励行为的动机，以及奖励消耗期间的享乐性口部运动。
