Manipulating Memory Traces in the Hippocampus

The hippocampus is thought to encode spatial and contextual memories in distinct groups of neurons called engram cells. Wiltgen\u27s lab was one of the first to confirm this experimentally by identifying active cells during learning and silencing them during memory retrieval. This was accomplished by combining transgenic reporter mice with optogenetic tools to selectively express light-sensitive proteins in active neurons during context fear conditioning. When these neurons were silenced, they found that memory retrieval was severely impaired. Inactivation of hippocampal neurons also prevented the reactivation of neocortical ensembles that were engaged during learning