Searching for engrams.

Recent advances in cellular imaging technologies together with novel genetic tools have enabled the observation of minute anatomical changes in the intact brain. This has elevated the search for physical correlates of memory, one of the longstanding questions in modern neurobiology, to a new level. Utilizing these new tools, several studies have recently been published pointing to subcellular structural changes occurring when the brain stores information about the environment. While most of these studies still fall short of investigating memory as commonly defined in neuropsychological terms, they are paving the way to more refined experiments, which come closer to the identification of true "memory traces." In the not too distant future we will be able to observe physical changes that occur during learning in the intact animal in real time, leading the way to understanding these processes in unprecedented detail.