Department of Biomedical Sciences, Marquette University, Milwaukee, WI, USA.
Synapse. 2021 Aug;75(8):e22202. doi: 10.1002/syn.22202. Epub 2021 May 3.
Animals appoint incentive value and learn to approach otherwise behaviorally inert stimuli if these stimuli come to predict the delivery of reward. Interestingly, this adaptive Pavlovian learning process has been implicated in behavioral control disorders, such as drug addiction. One brain region implicated in directing conditioned approach behavior is the prelimbic region of the prefrontal cortex. The present study employed in vivo electrophysiology in the prelimbic cortex to characterize the distribution of neural responses to the presence of a cue that had acquired incentive value after being associated with a primary reward. Male rats were trained in a Pavlovian autoshaping task in which a lever was presented prior to reward delivery. Following repeated pairings of lever availability and reward delivery, rats pressed the lever even though reward delivery was not contingent on any interaction with the lever. Neurons in the prelimbic cortex selectively encoded the presentation of the reward-predicting lever. Although the response was heterogeneous, most responsive neurons decreased their firing rate in response to the presence of the lever. These findings characterize the varied responses of prelimbic cortical neurons to reward cues and are consistent with evidence that the role of the prelimbic cortex in reward learning depends on the downstream target.
动物会指定激励价值，如果这些刺激开始预测奖励的发放，它们就会学会接近原本行为上惰性的刺激。有趣的是，这种适应性的巴甫洛夫学习过程与行为控制障碍有关，例如药物成瘾。一个与指导条件接近行为有关的大脑区域是前额叶皮层的前扣带回区域。本研究采用了活体电生理学技术，在前扣带回皮层中对与主要奖励相关联后获得激励价值的线索存在时的神经反应分布进行了特征描述。雄性大鼠在前自动塑造任务中接受训练，在该任务中，在奖励发放之前呈现杠杆。在反复将杠杆可用性与奖励发放配对后，即使奖励发放不依赖于与杠杆的任何交互，大鼠也会按压杠杆。前扣带回皮层中的神经元选择性地对奖励预测杠杆的呈现进行编码。尽管反应是异质的，但大多数反应性神经元的放电率会因杠杆的存在而降低。这些发现描述了前扣带回皮层神经元对奖励线索的不同反应，与以下证据一致，即前扣带回皮层在奖励学习中的作用取决于下游靶点。
