Tremblay L, Schultz W
Institute of Physiology and Program in Neuroscience, University of Fribourg, CH-1700 Fribourg, Switzerland.
J Neurophysiol. 2000 Apr;83(4):1864-76. doi: 10.1152/jn.2000.83.4.1864.
The orbitofrontal cortex appears to be involved in the control of voluntary, goal-directed behavior by motivational outcomes. This study investigated how orbitofrontal neurons process information about rewards in a task that depends on intact orbitofrontal functions. In a delayed go-nogo task, animals executed or withheld a reaching movement and obtained liquid or a conditioned sound as reinforcement. An initial instruction picture indicated the behavioral reaction to be performed (movement vs. nonmovement) and the reinforcer to be obtained (liquid vs. sound) after a subsequent trigger stimulus. We found task-related activations in 188 of 505 neurons in rostral orbitofrontal area 13, entire area 11, and lateral area 14. The principal task-related activations consisted of responses to instructions, activations preceding reinforcers, or responses to reinforcers. Most activations reflected the reinforcing event rather than other task components. Instruction responses occurred either in liquid- or sound-reinforced trials but rarely distinguished between movement and nonmovement reactions. These instruction responses reflected the predicted motivational outcome rather than the behavioral reaction necessary for obtaining that outcome. Activations preceding the reinforcer began slowly and terminated immediately after the reinforcer, even when the reinforcer occurred earlier or later than usually. These activations preceded usually the liquid reward but rarely the conditioned auditory reinforcer. The activations also preceded expected drops of liquid delivered outside the task, suggesting a primary appetitive rather than a task-reinforcing relationship that apparently was related to the expectation of reward. Responses after the reinforcer occurred in liquid- but rarely in sound-reinforced trials. Reward-preceding activations and reward responses were unrelated temporally to licking movements. Several neurons showed reward responses outside the task but instruction responses during the task, indicating a response transfer from primary reward to the reward-predicting instruction, possibly reflecting the temporal unpredictability of reward. In conclusion, orbitofrontal neurons report stimuli associated with reinforcers are concerned with the expectation of reward and detect reward delivery at trial end. These activities may contribute to the processing of reward information for the motivational control of goal-directed behavior.
眶额皮质似乎通过动机结果参与对自愿的、目标导向行为的控制。本研究调查了眶额神经元在一项依赖完整眶额功能的任务中如何处理有关奖励的信息。在一个延迟的“去/不去”任务中，动物执行或抑制伸手动作，并获得液体或条件化声音作为强化物。一张初始指示图片表明在随后的触发刺激后要执行的行为反应（动作与不动作）以及要获得的强化物（液体与声音）。我们在喙侧眶额区13、整个11区和外侧14区的505个神经元中的188个中发现了与任务相关的激活。主要的与任务相关的激活包括对指示的反应、强化物之前的激活或对强化物的反应。大多数激活反映的是强化事件而非其他任务成分。指示反应在液体强化或声音强化试验中都会出现，但很少区分动作和不动作反应。这些指示反应反映的是预期的动机结果，而非获得该结果所需的行为反应。强化物之前的激活开始缓慢，并在强化物出现后立即终止，即使强化物出现的时间比通常早或晚。这些激活通常先于液体奖励出现，但很少先于条件化听觉强化物出现。这些激活也先于任务外预期的液体滴落，表明存在一种主要的食欲性而非任务强化关系，这显然与奖励预期有关。强化物之后的反应出现在液体强化试验中，但很少出现在声音强化试验中。奖励之前的激活和奖励反应在时间上与舔舐动作无关。几个神经元在任务外表现出奖励反应，但在任务期间表现出指示反应，表明反应从初级奖励转移到了奖励预测指示，这可能反映了奖励的时间不可预测性。总之，眶额神经元报告与强化物相关的刺激，关注奖励预期，并在试验结束时检测奖励的发放。这些活动可能有助于处理奖励信息，以对目标导向行为进行动机控制。
