Reward value effects on reward timing

动物和人类需要了解何时有食物、水或配偶等重要资源可用。他们能够做到这一点的方法之一是识别在食物等资源可用之前的线索。随着时间的推移，它们可以提炼这种能力，并主要在食物即将获得的时候对这些暗示做出反应。要做到这一点，需要某种计时装置。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。主要使用人类、大鼠和鸽子的研究确定了一种形式的内部时钟，即大脑中的秒表，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、体温调节，甚至一些巨大的噪音都会影响人和动物的时间。我们实验室的实验发现，改变老鼠所获得的食物的价值，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，然后让它变得更大，老鼠似乎会预期它会比实际发生得更早。另一方面，如果我们降低了奖励的价值，例如，将更大的奖励变得更小，或者使奖励不那么容易被老鼠接受，它们的反应就像它们认为奖励应该比实际情况更晚才能获得一样。这可能看起来很奇怪，但我们人类在日常生活中会这样做。如果你知道你要去度假，你在工作或学校的最后一天似乎会拖拖拉拉。看来你的假期，你一直期待的事情，应该更早开始了。但为什么会是这样呢？这项提议旨在找出导致这种改变了对奖励发放时间的看法的机制。在内部时钟中有两种可能的机制负责：起搏器，秒表本身；或参考存储器，其中存储了所有先前经验的持续时间。我们还建议观察对时间感知的其他可能影响，例如对任务的注意力；老鼠的动机或唤醒水平；以及老鼠可能用来作为跟踪时间的替代方式的任何行为模式。这些调查的结果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可能如何改变这种感知。这与涉及冲动的工作尤其相关，例如调查赌博、成瘾、注意力缺陷多动障碍(ADHD)和许多其他疾病。在这些情况下，当奖励的延迟被操纵时，个人对奖励的价值有一种扭曲的看法。在这里，我们正在研究一个互惠的问题，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.