White N M, McDonald R J
Department of Psychology, McGill University, Montreal, Que., Canada.
Behav Brain Res. 1993 Jun 30;55(2):269-81. doi: 10.1016/0166-4328(93)90122-7.
This experiment examined the role of the lateral nucleus of the amygdala, the hippocampus and the dorsal striatum in the acquisition of a conditioned place preference (CPP). The CPP was established on a radial maze which was rotated before each daily trial so that only distal cues could be used to distinguish among locations on it. Each rat was assigned a paired location in which the arm contained food, and an unpaired location in which the arm was empty. A training trial consisted of 30-min confinements in the paired and unpaired locations on successive days. Groups of animals received between 1 and 4 training trials, after which they were tested for their preference between their two assigned locations with no food in either one. Normal animals acquired a CPP after 4 training trials, an instance of stimulus--reward learning. Electrolytic and neurotoxic lesions of the lateral nucleus of the amygdala prevented acquisition of the CPP in 4 training trials, suggesting that some function of this structure (or of a neural system that includes it) is required for acquisition and/or expression of stimulus--reward associations. Striatal lesions had no effect on the CPP. Fornix lesions facilitated acquisition of the CPP after 1-3 training trials, but no CPP was observed in animals with combined fornix and amygdala lesions, suggesting that exposure to the maze environment led to the processing of information in a hippocampal system that interfered with acquisition or expression of the amygdala-based CPP. Fornix lesions also increased the number of entries into maze arms on the test day, and concurrent amygdala lesions attenuated this increase. This finding suggests that the increase in arm entries may have been generated by the amygdala and suppressed by the hippocampus. Arm entries were interpreted as an instance of a particular type of exploratory behavior. Therefore, the present results suggest that a neural system including the lateral nucleus of the amygdala mediates both stimulus--reward learning and at least one form of exploration, possibly through its connections with the motor output system in ventral striatum. A hippocampal system appears to suppress or interfere with both of these behaviors in normal animals.
本实验研究了杏仁核外侧核、海马体和背侧纹状体在条件性位置偏爱（CPP）习得过程中的作用。CPP是在一个放射状迷宫上建立的，每天每次试验前都会旋转迷宫，以便仅通过远端线索来区分其上的位置。每只大鼠都被分配了一个配对位置，该位置的臂中放置有食物，以及一个非配对位置，该位置的臂是空的。一次训练试验包括连续几天在配对和非配对位置各禁闭30分钟。将动物分成几组，每组接受1至4次训练试验，之后在两个分配位置均无食物的情况下测试它们对这两个位置的偏爱情况。正常动物在经过4次训练试验后获得了CPP，这是刺激-奖赏学习的一个实例。对杏仁核外侧核进行电解损伤和神经毒性损伤后，动物在4次训练试验中均未能获得CPP，这表明该结构（或包含该结构的神经系统）的某些功能是刺激-奖赏关联的习得和/或表达所必需的。纹状体损伤对CPP没有影响。穹窿损伤在1至3次训练试验后促进了CPP的习得，但在同时有穹窿和杏仁核损伤的动物中未观察到CPP，这表明暴露于迷宫环境会导致海马体系统对信息进行处理，从而干扰基于杏仁核的CPP的习得或表达。穹窿损伤还增加了测试当天进入迷宫臂的次数，而同时进行的杏仁核损伤减弱了这种增加。这一发现表明，进入迷宫臂次数的增加可能是由杏仁核产生的，并受到海马体的抑制。进入迷宫臂被解释为一种特定类型探索行为的实例。因此，目前的结果表明，一个包括杏仁核外侧核的神经系统可能通过其与腹侧纹状体运动输出系统的连接来介导刺激-奖赏学习和至少一种形式的探索。在正常动物中，海马体系统似乎会抑制或干扰这两种行为。
