Topic: memory engram cells

Memories are thought to be encoded in the brain via synaptic strengthening among memory engram cells. Still, it has not been possible to observe if learning potentiates synaptic connections and simultaneously show that these changes are causally related to memory expression (i.e., they occur in engram neurons). We used a novel engram allocation-based approach to observe synaptic changes in engram neurons upon learning in-vivo. Using optogenetics, we assigned selected Medial Entorhinal Cortex (MEC) neurons to a context fear memory. This takes advantage of the fact that neurons with more excitab

Memory engram cells, activated by learning, undergo input-specific augmentation in their synaptic connectivity (structure, strength and efficacy) to facilitate memory storage and recall. However, only a subset of these cells is reactivated upon retrieval, indicating potential differences in engram cell synaptic connectivity. In this study, we investigated structural synaptic connectivity differences between reactivated and non-reactivated hippocampal CA1 engram cells under conditions of neutral and aversive contextual memory valence. A combination of eGRASP (enhanced green fluorescent protein