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Reversible plasticity of fear memory-encoding amygdala synaptic circuits even after fear memory consolidation

Cited 17 time in Web of Science Cited 18 time in Scopus

Hong, Ingie; Kim, Jihye; Lee, Junuk; Park, Sungmo; Kim, Jeongyeon; Park, Kyungjoon; Lee, Sukwon; Park, Sang-Hyun; Lee, Seungbok; Choi, Sukwoo; Eom, Khee Dong; Kim, Hyun; Lee, Hyun Woo; An, Bobae; Song, Beomjong

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Public Library of Science
PLoS ONE; Vol.6, No.9, pp,e24260
It is generally believed that after memory consolidation, memory-encoding synaptic circuits are persistently modified and become less plastic. This, however, may hinder the remaining capacity of information storage in a given neural circuit. Here we consider the hypothesis that memory-encoding synaptic circuits still retain reversible plasticity even after memory consolidation. To test this, we employed a protocol of auditory fear conditioning which recruited the vast majority of the thalamic input synaptic circuit to the lateral amygdala (T-LA synaptic circuit; a storage site for fear memory) with fear conditioning-induced synaptic plasticity. Subsequently the fear memory-encoding synaptic circuits were challenged with fear extinction and re-conditioning to determine whether these circuits exhibit reversible plasticity. We found that fear memory-encoding T-LA synaptic circuit exhibited dynamic efficacy changes in tight correlation with fear memory strength even after fear memory consolidation. Initial conditioning or re-conditioning brought T-LA synaptic circuit near the ceiling of their modification range (occluding LTP and enhancing depotentiation in brain slices prepared from conditioned or re-conditioned rats), while extinction reversed this change (reinstating LTP and occluding depotentiation in brain slices prepared from extinguished rats). Consistently, fear conditioning-induced synaptic potentiation at T-LA synapses was functionally reversed by extinction and reinstated by subsequent re-conditioning. These results suggest reversible plasticity of fear memory-encoding circuits even after fear memory consolidation. This reversible plasticity of memory-encoding synapses may be involved in updating the contents of original memory even after memory consolidation. ⓒ 2011 Hong et al.
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