Reward value effects on reward timing

动物和人类需要知道什么时候可以获得食物、水或配偶等重要资源。它们做到这一点的方法之一是识别食物等资源可用性之前的线索。随着时间的推移，他们可以完善这种能力，并对这些线索做出反应，主要是在食物可以获得的时候。要做到这一点，需要某种定时装置。人类可以使用手表或类似的机械装置；其他物种没有这种奢侈。主要以人类、老鼠和鸽子为实验对象的研究已经确定，大脑中有一种内部时钟，类似于秒表，可以启动、停止和重置。与人类使用的秒表不同，这些内部时钟并不总是准确的；一些药物，体温的调节，甚至一些大声的噪音都会影响人和动物的计时方式。我们实验室的实验发现，改变老鼠获得的食物价值或“奖励”似乎会影响它们对奖励何时发生的感知。如果我们用一个小奖励来训练老鼠，然后把它变大，老鼠似乎期望它比实际发生的要早。另一方面，如果我们降低奖励的价值，比如把一个大的奖励变小，或者让老鼠不那么喜欢这个奖励，它们的反应就好像它们认为奖励应该比实际情况晚一些才会出现。这可能看起来很奇怪，但我们人类在日常生活中都会这样做。如果你知道你要去度假，你在工作或学校的最后一天似乎拖了。看来你的假期，你期待已久的事情，应该早点开始了。但为什么会这样呢？这一提议旨在发现这种对奖励交付时间的感知改变的机制。在生物钟内部有两种可能的机制；起搏器，秒表本身；或者参考存储器，其中存储了所有先前经历的持续时间。我们还建议研究对时间感知的其他可能影响，例如对任务的注意力；大鼠的动机或觉醒水平；以及老鼠可能使用的任何行为模式作为跟踪时间的替代方法。这些调查的结果将有望更好地理解所有物种预测奖励时间的方式，以及改变奖励的价值如何改变这种感知。这与涉及冲动的工作尤其相关，比如对赌博、成瘾、注意力缺陷多动障碍（ADHD）和许多其他疾病的调查。在这些情况下，当奖励的延迟被操纵时，个体对奖励的价值有一种扭曲的感知。在这里，我们关注的是一个相互的问题，即为什么当奖励的价值被操纵时，对奖励延迟的感知会被扭曲。

Animals and people need to learn when important resources such as food, water, or a mate are going to be available. One of the ways they can do this is to recognise cues that precede the availability of a resource such as food. Over time, they can refine this ability and respond to these cues primarily around the time that food is going to be obtainable. To do this some kind of timing device is required. Humans can use a watch or a similar mechanical device; other species do not have this luxury. Work using primarily humans, rats and pigeons has determined that a form of internal clock, a sort of stopwatch in the brain, can be started, stopped and reset. Unlike the stopwatches humans use, these internal clocks are not always accurate; some drugs, modulations in body temperature and even some loud noises can affect the way in which people and animals time. Experiments in our laboratory have found that changing the value of the food, or 'reward', that rats receive seems to affect their perceptions of when the reward will occur. If we train rats on a small reward and then make it larger, the rats seem to expect it to occur sooner than it actually does. If, on the other hand we decrease the value of the reward, for instance making a larger reward smaller, or making the reward less palatable to the rat, they respond as if they believe the reward should be available later than it actually is. This may seem strange, but we humans do this in everyday life. If you know you are going on holiday, your last day at work or school seems to drag. It seems as though your holiday, the thing you have been looking forward to, should start sooner. But why should this be? This proposal aims to find the mechanism responsible for this altered perception of the time of reward delivery. Within the internal clock are two possible mechanisms that could be responsible; the pacemaker, the stopwatch itself; or the reference memory, where all the previously experienced durations are stored. We are also proposing to look at other possible influences on the perception of time, such as the attention given to the task; the motivation or arousal level of the rat; and also any behaviour patterns the rat may be using as an alternative way of tracking time. The results of these investigations will hopefully provide a better understanding of the way all species predict the time to reward and how changing the value of the reward may alter this perception. This is especially relevant to work involving impulsivity, such as investigations into gambling, addiction, attention deficit hyperactivity disorder (ADHD) and a host of other conditions. In these cases individuals have a distorted perception of the value of a reward when the delay to that reward is manipulated. Here we are looking at the reciprocal question of why the perception of the delay to a reward is distorted when the value of that reward is manipulated.