Abstract
A memory trace, also known as a memory engram, is theorized to be a mechanism for physical memory storage in the brain ( Silva et al., 2009 ; Josselyn, 2010) and memory trace is associated with a specific population of neurons ( Liu et al., 2012 ; Ramirez et al., 2013 ). Labeling and stimulating those neurons will activate the memory trace ( Liu et al., 2012 ; Ramirez et al., 2013 ). Memory appears to be spread over different regions of the brain rather than being localized to one area. Therefore, the methods used to trace memory have the ability to improve our understanding of neuronal circuits. In this protocol, we introduce a doxycycline-inducible expression system to label the specific neurons associated with the original memory trace.