NEURAL MECHANISMS OF MOTIVATION AND REWARD

作为研究猴子动机的模型，我们开发了一种 行为任务中，猴子的表现水平可以被控制， 被拖走了 猴子被要求完成一系列的一个，两个，或 三次试训成功获得奖励。 在每次试验中， 必须检测电视监视器上小方块的颜色变化。 提示 位于小正方形上方或下方的刺激改变亮度， 当下一次成功完成的试验 一个奖励。 在一系列试验中，猴子们被奖励了 当试验进行时，他们的成功率最高 执行将得到奖励，并以最低的成功率时， 动物在接受试验之前必须正确地进行其他试验。 奖励 他们释放操纵杆的反应时间遵循 类似的趋势，最快的反应时间发生在试验中， 会直接导致奖励 猴子的行为就像是 当成功后，奖励将被交付， 完成下一次审判。 我们将这个结果模拟为一个能量面 在这一点上， 刺激条件与奖励传递时发生刺激条件相匹配， 有了。 当静脉注射可卡因作为奖励在一个街区的 试验中，性能水平下降， 在实验中，猴子会得到奖励， 必须做更多的工作才能获得奖励。 然而，猴子的反应 奖励赛的时间更短。 单个神经元 腹侧纹状体表现出与果汁输送相关的反应 奖励，以工作量已完成时，该系列的 获得奖励所需的试炼不止一次。 我们建议 这些神经元将提供良好的神经信号， 复杂的行为得到了奖励。 当神经元在 可卡因是奖励，与那些对果汁有反应的人不同， 他们同样强烈地回应， 没有

As a model for studying motivation using monkeys, we have developed a behavioral task in which the monkey's level of performance can be con- trolled. The monkey is required to complete a series of one, two, or three successful trials to obtain a reward. In each trial the monkey must detect a color change in a small square on a TV monitor. A cue stimulus located above or below the small square changes brightness so that it is brightest when the next successfully completed trial will lead to a reward. In blocks of trials where the monkeys were rewarded with juice they performed with the highest success rate when the trial being performed would be rewarded and with the lowest success rate when the animal would have to perform other trials correctly before receiving a reward. Their reaction times for release of the manipulandum followed a similar trend, with the fastest reaction time occurring on trials that would lead directly to a reward. The monkeys thus act as if they are trying harder when the reward will be delivered after the successful completion of the next trial. We model this result as an energy surface on which the greatest energy for task performance is available when the stimulus conditions match those that will occur when a reward is deliv- ered. When intravenous cocaine was used as the reward in a block of trials, the performance level dropped and there was no difference between trials where a reward would be delivered and ones where the monkey would have to do more work to obtain a reward. However, the monkeys' reaction times were still shorter in the rewarded trials. Single neurons in the ventral striatum showed responses related to the delivery of juice rewards, to the amount of work that had been completed when the series of trials needed to obtain a reward was more than one. We suggest that these neurons would provide a good neural signal for the reinforcement of complex behavior that was rewarded. The neurons that responded when cocaine was the reward were different than those that responded to juice, and they responded equally strongly whether the trial was rewarded or not.