华盛顿大学的研究人员利用分子成像技术跟踪大鼠大脑神经活动，发现位于大脑侧脑室下角前端上方的杏仁体(amygdala)是恐惧记忆存储的地方。

神经学家以前认为杏仁体和海马体都与恐惧情感产生有关，但是新的研究表明海马体只负责处理和传输信息，不能产生恐惧感。

最新研究中，研究人员将大鼠分为四组，把其中三组放在一个陌生环境中，并施予不同的电刺激。反复试验，通过观察大鼠行为确定产生恐惧记忆后将大鼠杀死。取脑切片成像后发现大脑中杏仁体是产生恐惧记忆的部位。（ 生物谷 Bioon.com）

生物谷推荐原始出处：

PLoS ONE 4(7): e6156. doi:10.1371/journal.pone.0006156

Functional Imaging of Stimulus Convergence in Amygdalar Neurons during Pavlovian Fear Conditioning

Sabiha K. Barot1,2, Ain Chung2, Jeansok J. Kim1,2, Ilene L. Bernstein1,2*

1 Program in Neurobiology & Behavior, University of Washington, Seattle, Washington, United States of America, 2 Department of Psychology, University of Washington, Seattle, Washington, United States of America

Background

Associative conditioning is a ubiquitous form of learning throughout the animal kingdom and fear conditioning is one of the most widely researched models for studying its neurobiological basis. Fear conditioning is also considered a model system for understanding phobias and anxiety disorders. A fundamental issue in fear conditioning regards the existence and location of neurons in the brain that receive convergent information about the conditioned stimulus (CS) and unconditioned stimulus (US) during the acquisition of conditioned fear memory. Convergent activation of neurons is generally viewed as a key event for fear learning, yet there has been almost no direct evidence of this critical event in the mammalian brain.

Methodology/Principal Findings

Here, we used Arc cellular compartmental analysis of temporal gene transcription by fluorescence in situ hybridization (catFISH) to identify neurons activated during single trial contextual fear conditioning in rats. To conform to temporal requirements of catFISH analysis we used a novel delayed contextual fear conditioning protocol which yields significant single- trial fear conditioning with temporal parameters amenable to catFISH analysis. Analysis yielded clear evidence that a population of BLA neurons receives convergent CS and US information at the time of the learning, that this only occurs when the CS-US arrangement is supportive of the learning, and that this process requires N-methyl-D-aspartate receptor activation. In contrast, CS-US convergence was not observed in dorsal hippocampus.

Conclusions/Significance

Based on the pattern of Arc activation seen in conditioning and control groups, we propose that a key requirement for CS-US convergence onto BLA neurons is the potentiation of US responding by prior exposure to a novel CS. Our results also support the view that contextual fear memories are encoded in the amygdala and that the role of dorsal hippocampus is to process and transmit contextual CS information.