The Elusive Engram: An Experiment in Memory Implantation
With each passing minute, multitudes of memories surge through our minds as we recollect past experiences and encode new ones. Since the dawn of introspective thought, humans have wondered where such experiences might be encoded, if a physical encoding is even possible . Fast forward to the 20th century and we now have pioneering works from the likes of Carl Lashley, acclaimed for his application of the term “engram” to describe a physical location and mechanism by which a specific memory is encoded, a memory trace so to speak . Lashley’s theories have proved highly influential (though his rat lesion methodologies have been criticized ), inspiring countless other neuroscientists such as Richard F. Thompson  and Howard Eichembaum  to embark on the quest to find the engram.
Fast forward to the 21st century and we continue to see groundbreaking work in engram research. A most recent study published in July 2013 titled “Creating a False Memory in the Hippocampus”  provides strong evidence for a functional memory engram through a novel memory implantation procedure. The study was conducted by the Susumu Tonegawa’s RIKEN-MIT Lab, which seeks to uncover the neural mechanisms underlying learning and memory. In this experiment, Tonegawa’s team of neuroscientists were able to implant artificial memories into the brains of mice using optogenetics, a technology in which the activity of specific neurons can be modulated by exposure to certain wavelengths of light. The specific memory manipulated in this study was a conditioned fear response to a mild electrical foot shock.