Neural signals in the monkey ventral striatum related to motivation for juice and cocaine rewards
Neural signals in the monkey ventral striatum related to motivation for juice and cocaine rewards
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DOI：
10.1152/jn.1996.75.3.1061
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发表时间：
1996-03-01
影响因子：
2.5
通讯作者：
Richmond, BJ
中科院分区：
文献类型：
--
作者：
Bowman, EM;Aigner, TG;Richmond, BJ
1.神经心理学、神经药理学和神经生理学的实验结果表明，腹侧纹状体参与奖赏相关的过程。我们设计了一个任务，使我们能够将感觉、运动和内部信号的影响分开，这样我们就可以研究腹侧纹状体神经元活动与不同动机状态之间的相关性。在这项任务中，视觉刺激被用来提示猴子在获得奖励方面的进展。在奖励试验中，猴子表现得更快，错误更少。在分析了三只猴子的行为结果后，我们记录了两只猴子的143个神经元，而它们在果汁或可卡因奖励下执行任务。在这项任务中，当一个小的视觉反应线索将颜色从红色（等待信号）改变为绿色（开始信号）时，猴子被要求松开对酒吧的控制。等待信号的持续时间是随机变化的。当猴子在信号出现后1秒内成功响应信号时，提示就会变成蓝色。在猴子成功完成一次、两次或三次试验后，就会获得奖励。时间表随机交错。第二个视觉刺激逐渐变亮或变暗，向猴子发出他们获得奖励的信号。这种区别性线索使猴子能够判断当前比率强化计划中剩余工作的比例。在三只猴子执行这项任务时收集了数据。随着猴子完成当前强化计划并获得奖励，平均反应时间变得更快，错误率下降，而模态反应时间没有变化。随着信号发出前等待时间的增加，猴子的反应更快，但他们的错误率几乎没有变化。从这些结果我们推断，在这个任务中动机和运动准备的影响是由不同的机制产生的，而不是由一个单一的机制subserving广义唤醒.在两只猴子执行获得果汁奖励的任务时，对138个腹侧纹状体神经元的活动进行了采样。在整个试验过程中，我们看到了活动的紧张性变化，我们看到了奖励后的阶段性活动。这些神经元的活动在果汁奖励试验中与在正确执行试验时没有奖励（或预期）明显不同。这些反应也很弱，但显着，相关的接近奖励的时间表需要一个以上的试验。猴子们努力获得静脉注射可卡因，而我们记录了62个神经元。对于其中的57个神经元，我们记录了猴子在一系列试验中的活动，在这些试验中，他们在自己服用可卡因的过程中，他们在果汁中工作。虽然对可卡因的反应比对果汁奖励的反应少（19对33%），但这种差异并不显著。神经元对可卡因和果汁奖励的反应特性是独立的;也就是说，当一个是奖励时，一个的反应不能预测另一个是奖励时的反应。此外，神经元活动失去了大部分奖励试验的选择性，也就是说，活动没有区分可卡因和假奖励之间的果汁和假奖励。我们的研究结果表明，可卡因行为的机制似乎与猴子口服果汁奖励时激活的机制不同。这一发现提出了一种有趣的可能性，即可卡因的作用可以选择性地减少，而不会阻止许多自然奖励的作用。
1. The results of neuropsychological, neuropharmacological, and neurophysiological experiments have implicated the ventral striatum in reward-related processes. We designed a task to allow us to separate the effects of sensory, motor, and internal signals so that we could study the correlation between the activity of neurons in the ventral striatum and different motivational states. In this task, a visual stimulus was used to cue the monkeys as to their progress toward earning a reward. The monkeys performed more quickly and with fewer mistakes in the rewarded trials. After analyzing the behavioral results from three monkeys, we recorded from 143 neurons from two of the monkeys while they performed the task with either juice or cocaine reward.2. In this task the monkey was required to release its grip on a bar when a small visual response cue changed colors from red (the wait signal) to green (the go signal). The duration of the wait signal was varied randomly. The cue became blue whenever the monkey successfully responded to the go signal within 1 s of its appearance. A reward was delivered after the monkey successfully completed one, two, or three trials. The schedules were randomly interleaved. A second visual stimulus that progressively brightened or dimmed signaled to the monkeys their progress toward earning a reward. This discriminative cue allowed the monkeys to judge the proportion of work remaining in the current ratio schedule of reinforcement. Data were collected from three monkeys while they performed this task.3. The average reaction times became faster and error rates declined as the monkeys progressed toward completing the current schedule of reinforcement and thereby earning a reward, whereas the modal reaction time did not change. As the duration of the wait period before the go signal increased, the monkeys reacted more quickly but their error rates scarcely changed. From these results we infer that the effects of motivation and motor readiness in this task are generated by separate mechanisms rather than by a single mechanism subserving generalized arousal.4. The activity of 138 ventral striatal neurons was sampled in two monkeys while they performed the task to earn juice reward. We saw tonic changes in activity throughout the trials, and we saw phasic activity following the reward. The activity of these neurons was markedly different during juice-rewarded trials than during correctly performed trials when no reward was forthcoming (or expected). The responses also were weakly, but significantly, related to the proximity of the reward in the schedules requiring more than one trial.5. The monkeys worked to obtain intravenous cocaine while we recorded 62 neurons. For 57 of the neurons, we recorded activity while the monkeys worked in blocks of trials during which they self-administered cocaine after blocks during which they worked for juice. Although fewer neurons responded to cocaine than to juice reward (19 vs. 33%), this difference was not significant. The neuronal response properties to cocaine and juice rewards were independent; that is, the responses when one was the reward one failed to predict the response when the other was the reward. In addition, the neuronal activity lost most of its selectivity for rewarded trials, i.e, the activity did not distinguish nearly as well between cocaine and sham rewards as between juice and sham rewards.6. Our results show that mechanisms by which cocaine acts do not appear to be the same as the ones activated when the monkeys were presented with an oral juice reward. This finding raises the intriguing possibility that the effects of cocaine could be reduced selectively without blocking the effects of many natural rewards.