Manipulating memory in space and time

One of the most fascinating aspects of an animal's brain is its ability to acquire new information from experience and retain this information over time as memory. The search for physical correlates of memory, the memory engram, has been a longstanding endeavor in modern neurobiology. Recent advances in transgenic and optogenetic tools have enabled the identification, visualization, and manipulations of natural, sensory-evoked, engram cells for a specific memory residing in specific brain regions. These studies are paving the way not only to understand memory mechanisms in unprecedented detail, but also to repair the abnormal state of mind associated with memory by engineering.