Department of Psychology, Korea University, Seoul 136-701, Korea.
J Neurosci. 2010 Jan 20;30(3):832-7. doi: 10.1523/JNEUROSCI.4145-09.2010.
We conducted a series of experiments to investigate the neural basis of the immediate extinction deficit, the lack of extinction when the interval between fear memory acquisition and extinction is short. In experiment 1, rats were given extinction training composed of 15 conditioned stimuli (CSs) either 15 min (immediate extinction: I-EXT) or 24 h (delayed extinction: D-EXT) after five tone-shock pairings. In the retention test performed 48 h after conditioning, I-EXT group exhibited significantly higher freezing than D-EXT group. In experiment 2, functional activation in the medial prefrontal cortex (mPFC) was detected using c-fos immunoreactivity. The number of Fos-positive neurons in the mPFC was significantly lower in I-EXT group than in D-EXT group. In experiment 3, rats received immediate extinction with microstimulation of the infralimbic region (IL) of the mPFC, either contingently paired or unpaired with the CS. In a subsequent retention test, the paired stimulation group exhibited decreased freezing relative to the unpaired stimulation group. Together, our results suggest that the immediate extinction deficit may be linked to the lack of neuronal activity in the IL.
我们进行了一系列实验，以研究即时消退缺陷的神经基础，即在恐惧记忆获得和消退之间的间隔较短时缺乏消退。在实验 1 中，大鼠接受了由 15 个条件刺激（CS）组成的消退训练，分别在 5 个音调-电击配对后 15 分钟（即时消退：I-EXT）或 24 小时（延迟消退：D-EXT）进行。在条件作用后 48 小时进行的保持测试中，I-EXT 组的冻结反应明显高于 D-EXT 组。在实验 2 中，使用 c-fos 免疫反应性检测内侧前额叶皮质（mPFC）的功能激活。I-EXT 组的 mPFC 中 Fos 阳性神经元的数量明显低于 D-EXT 组。在实验 3 中，大鼠接受了内侧前扣带皮层（IL）的即时消退微刺激，与 CS 有条件地或无条件地配对。在随后的保持测试中，配对刺激组的冻结反应相对于非配对刺激组减少。总之，我们的结果表明，即时消退缺陷可能与 IL 中的神经元活动缺乏有关。
