Schultz W
Institut de Physiologie, Université de Fribourg, Switzerland.
Rev Neurol (Paris). 1994 Aug-Sep;150(8-9):634-9.
In view of the behavioral deficits arising after lesions of midbrain dopamine systems, we recorded single dopamine neuron activity in monkeys which learned and performed reaction time tasks, delayed response tasks, and controlled, self-initiated movements. Dopamine neurons respond in a rather homogeneous fashion to salient external stimuli that attract the attention of the subject. Depending on the particular behavioral situation, dopamine neurons are activated by primary liquid and food rewards during learning or in the absence of predictive stimuli, by conditioned stimuli predicting reward and eliciting behavioral reactions, and by novel, unexpected stimuli. Thus, dopamine neurons signal the presence of reward-related, alerting stimuli that need to be processed by the subject with high priority. Besides these phasic responses, dopamine systems apparently operate also in a tonic mode, as inferred from the beneficial effects of dopamine receptor agonist drugs on Parkinsonian symptoms. Whereas the phasic responses may mediate alerting functions or possibly reward-directed learning, the tonic activity may be involved in maintaining states of behavioral alertness and thus enable-movements and cognitive processes. These data provide neurophysiological correlates for the involvement of dopamine neurons in central processes determining the behavioral reactivity of the subject to important environmental events, and possibly the learning of reward-directed behavior.
鉴于中脑多巴胺系统受损后出现的行为缺陷，我们记录了猴子中单个多巴胺神经元的活动，这些猴子学习并执行反应时间任务、延迟反应任务以及可控的自主运动。多巴胺神经元对吸引受试者注意力的显著外部刺激以相当一致的方式做出反应。根据特定的行为情境，多巴胺神经元在学习期间或没有预测性刺激时，由初级液体和食物奖励激活；由预测奖励并引发行为反应的条件刺激激活；以及由新颖、意外的刺激激活。因此，多巴胺神经元发出与奖励相关的、需要受试者高度优先处理的警觉刺激的信号。除了这些相位反应外，从多巴胺受体激动剂药物对帕金森症状的有益作用推断，多巴胺系统显然也以紧张性模式运作。相位反应可能介导警觉功能或可能的奖励导向学习，而紧张性活动可能参与维持行为警觉状态，从而实现运动和认知过程。这些数据为多巴胺神经元参与中枢过程提供了神经生理学关联，这些中枢过程决定了受试者对重要环境事件的行为反应性，并可能涉及奖励导向行为的学习。
