TY - JOUR TI - Amount of fear extinction changes its underlying mechanisms AU - An, Bobae AU - Kim, Jihye AU - Park, Kyungjoon AU - Lee, Sukwon AU - Song, Sukwoon AU - Choi, Sukwoo A2 - Costa, Rui M VL - 6 PY - 2017 DA - 2017/07/03 SP - e25224 C1 - eLife 2017;6:e25224 DO - 10.7554/eLife.25224 UR - https://doi.org/10.7554/eLife.25224 AB - There has been a longstanding debate on whether original fear memory is inhibited or erased after extinction. One possibility that reconciles this uncertainty is that the inhibition and erasure mechanisms are engaged in different phases (early or late) of extinction. In this study, using single-session extinction training and its repetition (multiple-session extinction training), we investigated the inhibition and erasure mechanisms in the prefrontal cortex and amygdala of rats, where neural circuits underlying extinction reside. The inhibition mechanism was prevalent with single-session extinction training but faded when single-session extinction training was repeated. In contrast, the erasure mechanism became prevalent when single-session extinction training was repeated. Moreover, ablating the intercalated neurons of amygdala, which are responsible for maintaining extinction-induced inhibition, was no longer effective in multiple-session extinction training. We propose that the inhibition mechanism operates primarily in the early phase of extinction training, and the erasure mechanism takes over after that. KW - fear extinction KW - lateral amygdala KW - prefrontal cortex KW - basal nucleus of amygdala KW - amygdala intercalated neurons JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -