Quirk Gregory J
Department of Physiology, Ponce School of Medicine, Ponce, Puerto Rico 00732, USA.
Learn Mem. 2002 Nov-Dec;9(6):402-7. doi: 10.1101/lm.49602.
Conditioned fear responses to a tone paired with footshock rapidly extinguish when the tone is presented in the absence of the shock. Rather than erase conditioning, extinction is thought to involve the formation of new memory. In support of this, extinguished freezing spontaneously recovers with the passage of time. It is not known, however, how long extinction memory lasts or whether extinction interferes with consolidation of conditioning if given on the same day. To address this, we gave rats 7 trials of auditory fear conditioning followed 1 h later by 20 extinction trials, and tested for spontaneous recovery after a delay of 0, 1, 2, 4, 6, 10, or 14 d. Conditioned freezing to the tone gradually recovered with time to reach 100% by day 10. No-extinction controls indicated that the increase in freezing with time was not owing to incubation of conditioning memory. Complete spontaneous recovery indicates that extinction training given 1 h after conditioning does not interfere with the consolidation of conditioning memory. Despite complete recovery of freezing, rats showed savings in their rate of re-extinction, indicating persistence of extinction memory. These data support the idea that conditioning and extinction of fear are learned by independent systems, each able to retain a long-term memory.
当在没有电击的情况下呈现音调时，对与足部电击配对的音调的条件性恐惧反应会迅速消退。消退并非消除条件作用，而是被认为涉及新记忆的形成。支持这一观点的是，消退后的僵住反应会随着时间的推移自发恢复。然而，尚不清楚消退记忆能持续多久，或者如果在同一天进行消退是否会干扰条件作用的巩固。为了解决这个问题，我们对大鼠进行了7次听觉恐惧条件训练，1小时后进行20次消退训练，并在0、1、2、4、6、10或14天的延迟后测试自发恢复情况。对音调的条件性僵住反应随时间逐渐恢复，到第10天时达到100%。未进行消退的对照组表明，僵住反应随时间的增加并非由于条件作用记忆的潜伏期延长。完全的自发恢复表明，在条件训练后1小时进行的消退训练不会干扰条件作用记忆的巩固。尽管僵住反应完全恢复，但大鼠在再次消退的速率上表现出节省，表明消退记忆持续存在。这些数据支持了这样一种观点，即恐惧的条件作用和消退是由独立的系统学习的，每个系统都能够保留长期记忆。
