Time processing in stimulant users: Impulsivity and temporal discounting

描述（由申请人提供）：药物使用是美国的一个重要问题。然而，导致和支持药物滥用的复杂和多方面的机制只是模糊地了解。冲动增加在吸毒者中很常见，并且被认为是有非法药物问题的个人的一个重要特征。冲动性可以用时间折现范式进行实验量化。时间折扣指的是现在发生的奖励比未来某个时间发生的奖励更有价值的现象。关于时间折现（以及冲动性）的一个研究很少的方面是个体如何处理时间。因此，我们的建议旨在研究使用兴奋剂并有过渡到兴奋剂依赖风险的年轻人（18-21岁）的时间折扣与主观和客观时间感知测量之间的关系。这项提议的研究是基于这样的假设，即这些个体，相对于年龄和教育程度相匹配的比较对象，由于时间感的改变而表现出增强的时间折扣。具体目的是：(1)我们将评估使用兴奋剂和匹配对照的年轻人在决策任务中的延迟贴现与主观和客观时间感知测量之间的关系；(2)我们将评估未使用兴奋剂的年轻人在决策任务和时间估计任务中延迟贴现的功能磁共振成像激活关系。这些研究基于这样的假设，即冲动性，用时间折现来衡量，依赖于对当前时间的主观关注和对时间间隔持续时间的高估。我们将在健康志愿者的时间贴现和时间估计任务中使用功能磁共振成像来阐明这两个过程是否有相似的神经基质。有人提出，利用功能性神经成像来研究个体如何处理时间，以及他们如何处理当前和未来的奖励，可以增强我们对冲动的生物学基础的理解。此外，更好地理解时间折扣背后的神经机制可能为我们研究成瘾风险的生物学基础提供一个标记。目前的研究将为治疗方案提供信息，以创建干预策略，操纵奖励的时间延迟，以形成更具适应性的行为。

DESCRIPTION (provided by applicant): Drug use is an important problem in the US. However, the complex and multifaceted mechanisms that lead to and support drug abuse are only vaguely understood. Increased impulsivity is commonly observed in drug users and is thought to be an important trait of individuals who have problems with illicit drugs. Impulsivity can be quantified experimentally using temporal discounting paradigms. Temporal discounting refers to the phenomenon that a reward, which occurs in the present time is valued more than rewards that occur some time in future. A poorly studied aspect of temporal discounting (and therefore impulsivity) is how individuals process time. Therefore, our proposal aims to examine the relationship between temporal discounting and subjective and objective measures of time perception in young adults (age 18-21) who use stimulants and are of risk for transition to stimulant dependence. The proposed study is based on the hypothesis that these individuals, relative to age and education matched comparison subjects show enhanced temporal discounting due to an altered sense of time. The specific aims are: (1) we will evaluate the relationship between delayed discounting in a decision making task and in subjective and objective measures of time perception in young adults who use stimulants and in matched controls; (2) we will evaluate the relationship of functional magnetic resonance imaging activation between delayed discounting in a decision making task and a time estimation task in young adults without stimulants use. These studies are based on the assumption that impulsivity, measured with temporal discounting, is dependent on a subjective focus on the present time and an overestimation of the duration of time intervals. We will use functional magnetic resonance imaging during temporal discounting and time estimation tasks in healthy volunteers to elucidate whether similar neural substrates underlie both processes. It is proposed that examining how individuals process time to how they process current versus future rewards using functional neuroimaging enhances our understanding of the biological underpinnings of impulsivity. Moreover, a better understanding of the neural mechanisms underlying temporal discounting may provide us with a marker to study the biological basis of risk for addiction. The current study will inform treatment programs to create intervention strategies that manipulate the temporal delay of rewards to shape more adaptive behavior.