MIT Scientists Demonstrate Memories Reside In Neurons

Reading time: 2 minutes

Neuroscientists — scientists who study the brain — have long attempted to understand the nature of memory. Engrams, or complete memories that are encoded in the brain, now appear to be stored physically as opposed to conceptually, according to research published in the journal Nature [1].

Mouse hippocampus

Explains lead researcher Susumu Tonegawa of MIT:

We demonstrate that behavior based on high-level cognition, such as the expression of a specific memory, can be generated in a mammal by highly specific physical activation of a specific small subpopulation of brain cells, in this case by light.

The researchers altered a small portion of the brains of some mice, causing the cells to produce light-sensitive proteins. They then put the mice in a specific environment and delivered a mild shock, causing the mice to fear the environment. Later, they stimulated the brain cells with light. This caused the mice to experience fear, even though they were no longer in the environment in which they’d been shocked. The light-sensitive cells were the ones that had encoded the fear memory.

The researchers hope that this work will help to elucidate the nature of how the brain encodes memories, which could be relevant to work with patients who have lost memories due to disease, aging or injury.

Source: Massachusetts Institute of Technology


  1. Liu et al. Optogenetic stimulation of a hippocampal engram activates fear memory recall. Nature. 2012 Mar 22. doi: 10.1038/nature11028. [Epub ahead of print].
    View abstract
About the Author

Walter Jessen, Ph.D. is a Data Scientist, Digital Biologist, and Knowledge Engineer. His primary focus is to build and support expert systems, including AI (artificial intelligence) and user-generated platforms, and to identify and develop methods to capture, organize, integrate, and make accessible company knowledge. His research interests include disease biology modeling and biomarker identification. He is also a Principal at Highlight Health Media, which publishes Highlight HEALTH, and lead writer at Highlight HEALTH.