Ensembles of synaptic networks are known to underlie cognitive functions, and the connections between engram neurons are enhanced during memory formation. Study from the researchers led by Prof. Bong-Kiun Kaang and Prof. Hye Yoon Park, identified the in vivo dynamics of synapses that underlie fear memory formation and extinction in living brains.
The researchers enabled the observation of identical synapses in multiple time points by adapting longitudinal two-photon imaging to dual-eGRASP system for the first time. Synapses between engram cells specifically underwent synaptogenesis during memory formation, while memory extinction led to their correlated disappearance. Moreover, the particular formation of new synapses resulted in the clustering of synaptic engrams.
Prof. Kaang said that "We showed for the first time how the synaptic engrams change within identical individuals according to different memory states". “This adaptation of dual-eGRASP system will open the possibility for the longitudinal observation of various synaptic networks.”, “We also expect that our findings will provide a basis to an advanced understanding of engram networks”, Prof. Kaang said.
Current Biology
Hippocampal engram networks for fear memory recruit new synapses and modify pre-existing synapses in vivo