Villaruel Franz R, Chaudhri Nadia
Center for Studies in Behavioral Neurobiology/Groupe de Recherche en Neurobiologie Comportementale, Department of Psychology, Concordia University Montreal, QC, Canada.
Front Behav Neurosci. 2016 Dec 26;10:238. doi: 10.3389/fnbeh.2016.00238. eCollection 2016.
Individual differences exist in the attribution of incentive salience to conditioned stimuli associated with food. Here, we investigated whether individual differences also manifested with a Pavlovian alcohol conditioned stimulus (CS). We compiled data from five experiments that used a Pavlovian autoshaping paradigm and tests of conditioned reinforcement. In all experiments, male, Long-Evans rats with unrestricted access to food and water were acclimated to 15% ethanol. Next, rats received Pavlovian autoshaping training, in which a 10 s presentation of a retractable lever served as the CS and 0.2 mL of 15% ethanol served as the unconditioned stimulus (US). Finally, rats underwent conditioned reinforcement tests in which nose-pokes to an active aperture led to brief presentations of the lever-CS, but nose-pokes to an inactive aperture had no consequence. Rats were categorized as sign-trackers, goal-trackers and intermediates based on a response bias score that reflected their tendencies to sign-track or goal-track at different times during training. We found that distinct groups of rats either consistently interacted with the lever-CS ("sign-trackers") or routinely approached the port during the lever-CS ("goal-trackers") across a majority of the training sessions. However, some individuals ("shifted sign-trackers") with an early tendency to goal-track later shifted to comparable asymptotic levels of sign-tracking as the group identified as sign-trackers. The lever-CS functioned as a conditioned reinforcer for sign-trackers and shifted sign-trackers, but not for goal-trackers. These results provide evidence of robust individual differences in the extent to which a Pavlovian alcohol cue gains incentive salience and functions as a conditioned reinforcer.
在将与食物相关的条件刺激赋予动机显著性方面存在个体差异。在此，我们研究了个体差异是否也表现在巴甫洛夫式酒精条件刺激（CS）中。我们汇总了五个实验的数据，这些实验采用了巴甫洛夫式自动形成范式和条件强化测试。在所有实验中，可自由获取食物和水的雄性长 Evans 大鼠适应了 15%的乙醇。接下来，大鼠接受巴甫洛夫式自动形成训练，其中可伸缩杠杆的 10 秒呈现作为条件刺激（CS），0.2 毫升 15%的乙醇作为非条件刺激（US）。最后，大鼠接受条件强化测试，在测试中，向活动孔的鼻触会导致杠杆 CS 的短暂呈现，但向非活动孔的鼻触则没有结果。根据反映其在训练不同时间进行信号追踪或目标追踪倾向的反应偏差分数，将大鼠分为信号追踪者、目标追踪者和中间类型。我们发现，不同组的大鼠在大多数训练过程中要么始终与杠杆 CS 相互作用（“信号追踪者”），要么在杠杆 CS 期间常规接近端口（“目标追踪者”）。然而，一些早期有目标追踪倾向的个体（“转变的信号追踪者”）后来转变为与被确定为信号追踪者的组相当的渐近信号追踪水平。杠杆 CS 对信号追踪者和转变的信号追踪者起条件强化物的作用，但对目标追踪者不起作用。这些结果提供了证据，表明在巴甫洛夫式酒精线索获得动机显著性并作为条件强化物的程度上存在显著的个体差异。
