Cain Mary E, Green Thomas A, Bardo Michael T
Kansas State University, Department of Psychology, 469 Bluemont Hall, Manhattan, KS 66506-5302, United States.
Behav Processes. 2006 Nov 1;73(3):360-6. doi: 10.1016/j.beproc.2006.08.007. Epub 2006 Sep 20.
Previous research has demonstrated that rats reared in an enriched condition (EC) with novel objects and social partners self-administer less amphetamine compared to rats raised in an isolated condition (IC). However, it is unclear if the enrichment-induced decrease in stimulant self-administration generalizes to non-drug rewards such as those provided by novel environmental stimuli. In the current study, EC, IC, and social condition (SC) rats were raised from 21 to 51 days of age before being tested in a two-lever operant conditioning chamber in which responding on one lever (active lever) resulted in illumination of a cue light. In Experiment 1, rats were initially assessed for baseline responding (no contingency) and then the contingent light was introduced. EC rats responded less than IC rats for the contingent light stimulus; however, EC rats also displayed a lower rate of baseline responding. In Experiment 2, rats were trained initially to lever press for a sucrose reward to decrease differences in baseline responding. While sucrose pretraining decreased baseline response differences between groups, EC rats still responded less for the contingent light stimulus than IC or SC rats. These results suggest that environmental enrichment decreases the incentive value of visual novelty.
先前的研究表明，与饲养在隔离环境（IC）中的大鼠相比，饲养在丰富环境（EC）中有新奇物品和社交伙伴的大鼠自我给药的苯丙胺较少。然而，尚不清楚丰富环境诱导的兴奋剂自我给药减少是否适用于非药物奖励，例如由新奇环境刺激提供的奖励。在当前的研究中，将EC、IC和社交环境（SC）大鼠从21日龄饲养到51日龄，然后在双杠杆操作性条件反射箱中进行测试，在该箱中，对一个杠杆（活动杠杆）的反应会导致提示灯亮起。在实验1中，最初评估大鼠的基线反应（无意外情况），然后引入意外出现的灯光。对于意外出现的灯光刺激，EC大鼠的反应少于IC大鼠；然而，EC大鼠的基线反应率也较低。在实验2中，最初训练大鼠按压杠杆以获得蔗糖奖励，以减少基线反应的差异。虽然蔗糖预训练减少了各组之间的基线反应差异，但EC大鼠对意外出现的灯光刺激的反应仍然少于IC或SC大鼠。这些结果表明，环境丰富化降低了视觉新奇性的激励价值。
