Pugh C R, Rudy J W
Department of Psychology, University of Colorado, Boulder, USA.
Dev Psychobiol. 1996 Mar;29(2):87-100. doi: 10.1002/(SICI)1098-2302(199603)29:2<87::AID-DEV1>3.0.CO;2-H.
Contextual fear conditioning by 18- and 23-day-old rats was compared in two training contexts, a transparent Plexiglas chamber or a black Plexiglas chamber. As measured by a conditioned defensive freezing response, older rats displayed more contextual fear than younger rats. At both ages conditioning was (a) stronger in the black chamber than in the clear chamber, (b) a nonmonotonic function of retention interval, with freezing being greater at the immediate and 24-hr retention interval than at the 10-min interval, and (c) preexposure to the context 24 hr before conditioning enhanced conditioned freezing observed at the 10-min retention interval. Additional experiments suggest that rats at both ages acquire independent representations of the visual and tactile features of the context. These results support Rudy and Morledge's (1994) hypothesis that contextual fear conditioning is mediated by both a short-term and a long-term memory system and that long-term memory for contextual fear requires the consolidation of a representation of the context. They challenge their view that there is a qualitative developmental difference in long-term memory processes between 18- and 23-day-old rats.
在两个训练环境中，即透明有机玻璃箱或黑色有机玻璃箱，对18日龄和23日龄大鼠的情境恐惧条件反射进行了比较。通过条件性防御性僵住反应来衡量，年长的大鼠比年幼的大鼠表现出更多的情境恐惧。在两个年龄段，条件反射均表现为：（a）在黑色箱中比在透明箱中更强；（b）是一个非单调的保持间隔函数，在即时和24小时保持间隔时的僵住程度比在10分钟间隔时更大；（c）在条件反射前24小时预先暴露于该环境，会增强在10分钟保持间隔时观察到的条件性僵住。额外的实验表明，两个年龄段的大鼠都能独立获取该环境视觉和触觉特征的表征。这些结果支持了鲁迪和莫尔莱奇（1994年）的假设，即情境恐惧条件反射由短期和长期记忆系统共同介导，且情境恐惧的长期记忆需要对该环境的表征进行巩固。它们对他们的观点提出了挑战，即在18日龄和23日龄大鼠的长期记忆过程中存在质的发育差异。
