Universidad Nacional de Córdoba, Córdoba, CP 5000 Argentina.
Instituto de Investigación Médica M. y M. Ferreyra (INIMEC - CONICET), Córdoba, C.P 5000, Argentina.
Dev Psychobiol. 2013 Mar;55(2):193-204. doi: 10.1002/dev.21011. Epub 2012 Jan 17.
The unconditioned stimulus pre-exposure effect (US-PE) refers to the interference paradigm in which acquisition of the conditioned response is retarded due to prior experience with the US. Most studies analyzing the psychological mechanisms underlying this effect have been conducted with adult rats. The most widely accepted hypothesis explains this effect as a contextual blocking effect. Contextual cues associated with the US block the conditioned stimulus (CS)-US association during conditioning. The modulatory role of a context devoid of distinctive olfactory attributes is not observable until approximately PD23 in rats, including modulation of interference paradigms such as latent inhibition or extinction. In this study, we analyzed US-PE in preweanling rats along with the role of the training context in this effect in terms of conditioned taste aversion preparation. Pre-exposure to LiCl before conditioning retarded the acquisition of taste aversion. The US-PE was observed in preweanling rats when, during pre-exposure, subjects were exposed to the conditioning context, and this effect was not attenuated either by the administration of the US in a familiar environment (Experiment 1a), or by the presence of an alternative, more salient context during pre-exposure (Experiment 1b). Additionally, the US-PE was still observed when the route by which the US was administered was changed between the pre-exposure and conditioning phases (Experiment 2a) as well as when the injection cues were removed during conditioning (Experiment 2b). These experiments show a strong US-PE in preweanling rats and fail to support the contextual blocking hypothesis, at least in this stage of ontogeny.
无条件刺激前暴露效应（US-PE）是指在先前接触到刺激的情况下，条件反应的获得受到干扰的干扰范式。大多数分析这种效应背后的心理机制的研究都是用成年大鼠进行的。最广泛接受的假设将这种效应解释为一种语境阻断效应。与刺激相关的语境线索在条件作用过程中阻断了条件刺激（CS）-刺激的关联。在大约 PD23 之前，包括调节潜伏抑制或消退等干扰范式的调节作用，在大鼠中是不可观察到的，而不具有独特嗅觉属性的语境的调节作用是不可观察到的。在这项研究中，我们分析了在新生儿期大鼠中的 US-PE，以及在条件味觉厌恶准备中，训练环境在这种效应中的作用。在条件作用之前，预先暴露于 LiCl 会延缓味觉厌恶的获得。在预暴露期间，当对象暴露于条件作用环境时，会观察到新生儿期大鼠中的 US-PE，并且这种效应既不会被在熟悉环境中给予刺激（实验 1a）减弱，也不会被在预暴露期间存在替代的、更显著的环境（实验 1b）减弱。此外，当在预暴露和条件作用阶段之间改变刺激的给药途径（实验 2a）时，以及当在条件作用期间去除注射线索（实验 2b）时，仍会观察到 US-PE。这些实验表明，新生儿期大鼠中存在强烈的 US-PE，并且至少在这个发育阶段，不支持语境阻断假设。
