Motivational control of goal-directed actions and habits

描述(由申请者提供)：本项目的目标是考察奖励线索对习惯性反应的动机效应。习惯是由于反复与强化配对而变得无意识和自动的行为(A.Dickinson，1985；H.H.Yen和B.J.Knowlton，2006)。它们是由环境中的刺激反射而来的，对反馈没有反应。因此，不令人惊讶的是，习惯在成瘾中扮演着重要角色，在成瘾中，不适应行为仍然存在，尽管随着时间的推移，药物失去了它们的奖励作用，并产生了许多不想要的、令人厌恶的后果(P.W.Kalivas和N.D.Volkow，2005；T.W.Robbins等，2008)。尽管奖励线索可以影响目标导向的行为，但其激发习惯性反应的程度尚未得到很好的描述(P.C.Holland，2004)。这一过程对我们理解成瘾至关重要，因为与毒品相关的环境线索是复发的主要原因(B.J.Everitt和T.W.Robbins，2005；P.W.Kalivas和N.D.Volkow，2005)。目前的实验将在小鼠身上使用操作性条件反射技术来检验这一动机过程。目的是确定与目标导向的行动相比，习惯是否对奖励线索特别敏感。动物将被训练按下杠杆以获得食物奖励。对于一些动物来说，这些奖励将以可变的间隔时间表(其中奖励取决于特定时间段过去后的反应)提供，这已被证明促进了习惯性反应。其他动物将接受比率时间表(奖励发放取决于做出的反应的数量)的训练，这已被证明有助于目标定向行动的习得(Dickinson，Nicholas，&Adams，1983；Yen，Knowlton，&Balleine，2004)。奖励线索的动机效应将通过两个过程来模拟：巴甫洛夫-工具性转移(PIT)和恢复(Wiltgen，Law，Ostlund，Mayford，&Balleine，2007)。在PIT过程中，环境线索通过巴甫洛夫条件作用获得作为奖励预测因子的意义，然后能够对工具性行为施加动机控制(Colwill，1988)。恢复是一种以结果为中介的工具性行为启动的分析，在这种分析中，奖励的交付本身启动并激励了一段时间的灭绝后的行为(Delamater，1997；Ostlund&Bale，2007)。我们的预测是，与目标导向的行为相比，习惯性反应更容易受到奖励提示(即反应速度加快)的影响。 与公共健康相关：这个项目将确定被称为习惯的自动、无意识行为是如何受到环境中的奖励线索的激励的。习惯通常是适应性的，因为它们允许可靠强化的行为变得高效和自动。然而，当他们产生像那些保持毒瘾的行为时，他们也可能是适应不良的。因此，了解奖赏线索激发习惯性反应的机制将有助于更好地理解药物复发及其潜在的神经机制。

DESCRIPTION (provided by applicant): The goal of this project is to examine the motivational effects of reward cues on habitual responding. Habits are behaviors that have become unconscious and automatic as a result of repeated pairings with reinforcement (A. Dickinson, 1985; H. H. Yin and B. J. Knowlton, 2006). They are elicited reflexively by stimuli in the environment and are not responsive to feedback. Not surprisingly then, habits play a major role in addiction where maladaptive behavior persists despite the fact that drugs lose their rewarding effects over time and produce many unwanted, aversive consequences (P. W. Kalivas and N. D. Volkow, 2005; T. W. Robbins et al., 2008). Although reward cues are known to influence goal-directed actions, the extent to which they motivate habitual responding has not been well characterized (P. C. Holland, 2004). This process is critical to our understanding of addiction, as environmental cues associated with drugs are major contributors to relapse (B. J. Everitt and T. W. Robbins, 2005; P. W. Kalivas and N. D. Volkow, 2005). The current experiments will examine this motivational process using operant conditioning techniques in mice. The purpose is to determine if habits are particularly responsive to reward cues compared to goal-directed actions. Animals will be trained to press levers in order to obtain food rewards. For some animals these rewards will be delivered on variable interval schedules (where reward is contingent on responding after a specific amount of time has passed) that have been shown to promote habitual responding. Other animals will be trained on ratio schedules (where reward delivery is contingent on the number of responses made), which have been shown to promote the acquisition of goal-directed actions (Dickinson, Nicholas, & Adams, 1983; Yin, Knowlton, & Balleine, 2004). The motivational effects of reward cues will be modeled with two procedures: Pavlovian-instrumental transfer (PIT) and reinstatement (Wiltgen, Law, Ostlund, Mayford, & Balleine, 2007). In the PIT procedure, environmental cues acquire significance as predictors of reward through Pavlovian conditioning and are then able to exert motivational control over instrumental actions (Colwill, 1988). Reinstatement is an assay of outcome-mediated initiation of instrumental behavior in which delivery of the reward itself primes and motivates behavior after a period of extinction (Delamater, 1997; Ostlund & Balline, 2007). Our prediction is that habitual responding will be more susceptible to the effects of reward cues (i.e. increased rate of responding) than goal-directed actions. PUBLIC HEALTH RELEVANCE: This project will determine how automatic, unconscious behaviors called habits are motivated by reward cues in the environment. Habits are normally adaptive because they allow reliably reinforced behaviors to become efficient and automatic. However, they can also be maladaptive when they produce behaviors like those that maintain drug addiction. Therefore, understanding the mechanisms by which reward cues motivate habitual responding will lead to a better understanding of drug relapse and its underlying neural mechanisms.