Carpenter Russ E, Summers Cliff H
Department of Biology, University of South Dakota, Vermillion, SD 57069, USA.
Neurobiol Learn Mem. 2009 May;91(4):415-23. doi: 10.1016/j.nlm.2009.01.009.
This paper describes a model of fear learning, in which subjects have an option of behavioral responses to impending social defeat. The model generates two types of learning: social avoidance and classical conditioning, dependent upon (1) escape from or (2) social subordination to an aggressor. We hypothesized that social stress provides the impetus as well as the necessary information to stimulate dichotomous goal-oriented learning. Specialized tanks were constructed to subject rainbow trout to a conditioning paradigm where the conditioned stimulus (CS) is cessation of tank water flow (water off) and the unconditioned stimulus (US) is social aggression from a larger conspecific. Following seven daily CS/US pairings, approximately half of the test fish learned to consistently escape the aggression to a neutral chamber through a small escape hole available only during the interaction. The learning curve for escaping fish was dramatic, with an 1100% improvement in escape time over 7 days. Fish that did not escape exhibited a 400% increase in plasma cortisol and altered brain monoamine response to presentation of the CS alone. Elevated plasma cortisol levels represent classical fear conditioning in non-escaping fish, while a lack of fear conditioning and a decreased latency to escape over the training period in escapers indicates learned escape.
本文描述了一种恐惧学习模型，在该模型中，实验对象对于即将到来的社会挫败有行为反应的选项。该模型产生两种类型的学习：社交回避和经典条件作用，这取决于（1）从攻击者那里逃脱或（2）在社会上从属于攻击者。我们假设社会压力为刺激二分法的目标导向学习提供了动力以及必要信息。建造了专门的水槽，使虹鳟鱼接受一种条件作用范式，其中条件刺激（CS）是水槽水流停止（水关闭），非条件刺激（US）是来自更大同种个体的社会攻击。在每天进行七次CS/US配对之后，大约一半的受试鱼学会了通过仅在互动期间可用的一个小逃生孔持续逃到一个中立空间以躲避攻击。逃脱鱼的学习曲线很显著，在7天内逃脱时间提高了1100%。未逃脱的鱼血浆皮质醇水平增加了400%，并且单独呈现CS时大脑单胺反应发生了改变。血浆皮质醇水平升高代表未逃脱鱼的经典恐惧条件作用，而逃脱鱼在训练期间缺乏恐惧条件作用且逃脱潜伏期缩短表明是习得性逃脱。
