Hollerman J R, Tremblay L, Schultz W
Institute of Physiology, University of Fribourg, CH-1700 Fribourg, Switzerland.
J Neurophysiol. 1998 Aug;80(2):947-63. doi: 10.1152/jn.1998.80.2.947.
Rewards constitute important goals for voluntary behavior. This study aimed to investigate how expected rewards influence behavior-related neuronal activity in the anterior striatum. In a delayed go-nogo task, monkeys executed or withheld a reaching movement and obtained liquid or sound as reinforcement. An initial instruction picture indicated the behavioral reaction to be performed and the reinforcer to be obtained after a subsequent trigger stimulus. Movements varied according to the reinforcers predicted by the instructions, suggesting that animals differentially expected the two outcomes. About 250 of nearly 1,500 neurons in anterior parts of caudate nucleus, putamen, and ventral striatum showed typical task-related activations that reflected the expectation of instructions and trigger, and the preparation, initiation, and execution of behavioral reactions. Strikingly, most task-related activations occurred only when liquid reward was delivered at trial end, rather than the reinforcing sound. Activations close to the time of reward showed similar preferences for liquid reward over the reinforcing sound, suggesting a relationship to the expectation or detection of the motivational outcome of the trial rather than to a "correct" or "end-of-trial" signal. By contrast, relatively few activations in the present task occurred irrespective of the type of reinforcement. In conclusion, many of the behavior-related neurons investigated in the anterior striatum were influenced by an upcoming primary liquid reward and did not appear to code behavioral acts in a motivationally neutral manner. Rather, these neurons incorporated information about the expected outcome into their behavior-related activity. The activations influenced by reward several seconds before its occurrence may constitute a neuronal basis for the retrograde effects of rewards on behavioral reactions.
奖励是自愿行为的重要目标。本研究旨在探究预期奖励如何影响前纹状体中与行为相关的神经元活动。在延迟的“去/不去”任务中，猴子执行或抑制伸手动作，并获得液体或声音作为强化物。初始指示图片表明了后续触发刺激后要执行的行为反应和要获得的强化物。动作根据指示所预测的强化物而有所不同，这表明动物对两种结果有不同的预期。在尾状核、壳核和腹侧纹状体前部的近1500个神经元中，约250个表现出典型的与任务相关的激活，这些激活反映了对指示和触发的预期，以及行为反应的准备、启动和执行。引人注目的是，大多数与任务相关的激活仅在试验结束时给予液体奖励时出现，而不是强化声音。接近奖励时间的激活对液体奖励的偏好高于强化声音，这表明与试验的动机结果的预期或检测有关，而不是与“正确”或“试验结束”信号有关。相比之下，在本任务中，无论强化类型如何，相对较少的激活发生。总之，在前纹状体中研究的许多与行为相关的神经元受到即将到来的主要液体奖励的影响，并且似乎不是以动机中性的方式编码行为动作。相反，这些神经元将关于预期结果的信息纳入其与行为相关的活动中。奖励出现前几秒受到奖励影响的激活可能构成奖励对行为反应逆行效应的神经元基础。
