Successful adaptation to the environment requires an accurate response to external threats by recalling specific memories. Memory formation and recall require engram cell activity and synaptic strengthening among activated neuronal ensembles. However, elucidation of the underlying neural substrates of associative fear memory has remained limited without a direct interrogation of extinction-induced changes of specific synapses that encode a specific auditory fear memory. Using dual-eGRASP (enhanced green fluorescent protein reconstitution across synaptic partners), we found that synapses among activated neuronal ensembles or activated synaptic ensembles showed a significantly larger spine morphology at auditory cortex (AC)-to-lateral amygdala (LA) projections after auditory fear conditioning in mice. Fear extinction reversed these enhanced synaptic ensemble spines, whereas re-conditioning with the same tone and shock restored the spine size of the synaptic ensemble. We suggest that synaptic ensembles encode and represent different fear memory states.

成功适应环境需要通过回忆特定记忆来准确应对外部威胁。记忆的形成和回忆需要激活的神经元集合之间的印迹细胞活动和突触强化。然而，如果没有直接询问编码特定听觉恐惧记忆的特定突触的灭绝引起的变化，对联想恐惧记忆的潜在神经基质的阐明仍然有限。使用双 eGRASP（跨突触伙伴的增强型绿色荧光蛋白重建），我们发现激活的神经元集合或激活的突触集合之间的突触在听觉皮层 (AC) 到外侧杏仁核 (LA) 投影后显示出明显更大的脊柱形态。小鼠的恐惧条件反射。恐惧消退逆转了这些增强的突触集合棘，而用相同的音调和冲击重新调节会恢复突触集合的棘大小。我们建议突触合奏编码并代表不同的恐惧记忆状态。