Ramos Sergio, López-Tolsa Gabriela E, Sjoberg Espen A, Pellón Ricardo
Animal Learning and Behavior Laboratory, Departamento de Psicología Básica I, Universidad Nacional de Educación a Distancia (UNED), Madrid, Spain.
Animal Behavior Laboratories, Department of Behavioral Science, Oslo Metropolitan University, Oslo, Norway.
Front Behav Neurosci. 2019 Nov 13;13:255. doi: 10.3389/fnbeh.2019.00255. eCollection 2019.
Delay discounting is the loss of the subjective value of an outcome as the time to its delivery increases. It has been suggested that organisms can become more tolerant of this delay when engaging in schedule-induced behaviors. Schedule-induced behaviors are those that develop at a high rate during intermittent reinforcement schedules without the need of arranged contingency to the reinforcer, and they have been considered as a model of compulsivity. There is evidence that relates compulsivity to greater delay discounting. The rate of delay discounting represents how impulsive the subject is, as the rate of discounting increases the higher the impulsivity. Thus, the main purpose of this study was to undertake a preliminary evaluation of whether developing schedule-induced behaviors affects performance in a delay-discounting task, by comparing spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) rats. The rats were exposed to a task that consisted of presenting the subjects with two levers: one produced a small, immediate food reinforcer while the other one produced a larger, delayed reinforcer. During Condition A, the levers were presented, and a water bottle and a running wheel were available in the conditioning chambers; during Condition B, only the levers were presented. SHR and WKY rats developed schedule-induced behaviors during Condition A and showed no difference in discounting rates, contradicting previous reports. Lick allocation during response-reinforcer delays and the inter-trial interval (ITI) showed, respectively, pre- and post-food distributions. Discounting rates during Condition B (when rats could not engage in schedule-induced behaviors) did not reach statistical significance difference among strains of animals, although it was observed a tendency for WKY to behave more self-controlled. Likewise it was not found any effect of schedule-induced behavior on discounting rates, however, a tendency for WKY rats to behave more impulsive during access to drink and run seems to tentatively support the idea of schedule-induced behavior as a model of compulsivity in those rats, being impulsivity simply defined as an excess in behavior.
延迟折扣是指随着结果交付时间的增加，结果的主观价值丧失。有人提出，生物体在进行日程诱导行为时，对这种延迟的耐受性会增强。日程诱导行为是指在间歇性强化日程中以高频率发展的行为，无需与强化物进行安排好的偶联，并且它们被视为一种强迫行为模型。有证据表明强迫行为与更大的延迟折扣有关。延迟折扣率代表了主体的冲动程度，因为折扣率越高，冲动性越高。因此，本研究的主要目的是通过比较自发性高血压大鼠（SHR）和Wistar-Kyoto（WKY）大鼠，初步评估发展日程诱导行为是否会影响延迟折扣任务的表现。大鼠被暴露于一项任务中，该任务包括向受试者呈现两个杠杆：一个产生小的即时食物强化物，而另一个产生大的延迟强化物。在A条件下，呈现杠杆，条件箱中有一个水瓶和一个跑步轮；在B条件下，只呈现杠杆。SHR和WKY大鼠在A条件下发展出了日程诱导行为，并且在折扣率上没有差异，这与之前的报告相矛盾。在反应-强化物延迟和试验间隔（ITI）期间的舔舐分配分别显示了食物前和食物后的分布。在B条件下（当大鼠不能进行日程诱导行为时），不同品系动物之间的折扣率没有达到统计学显著差异，尽管观察到WKY有更自我控制的倾向。同样，没有发现日程诱导行为对折扣率有任何影响，然而，WKY大鼠在饮水和跑步时表现出更冲动的倾向，这似乎初步支持了日程诱导行为作为这些大鼠强迫行为模型的观点，冲动性简单地定义为行为过度。
