Memories of positive associations get written onto DNA

Oak Ridge National Lab

Nerve cells communicate through short, fleeting pulses of electrical activity. Yet some memories stored in the brain can persist for decades. Research into how the nervous system bridges these two radically different time scales has been going on for decades, and a number of different ideas have picked up some experimental support.

For instance, based on their past activity, nerve cells can dictate which partners they make contact with or increase or decrease the strength of those connections—in essence, rewiring the brain as it develops and processes experiences. In addition, individual cells can make long-term changes in the genes that are active, locking specific behaviors in place. In a paper released by Nature Neuroscience, scientists have looked at the changes in gene expression associated with memories of positive associations and found that they are held in place by chemical modifications of the cells' DNA.

These chemical modifications fall under the broad (and somewhat poorly defined) category of epigenetic changes. Genetic changes involve alterations of the DNA sequence itself. Epigenetic changes, in contrast, alter how that DNA is processed within cells. They can be inherited as the cell divides and matures and, in rare cases, they're passed on to the next generation. In some cases, epigenetic changes simply involve how the DNA is packaged inside a cell, which controls how accessible it is to the enzymes that transcribe it for use in making proteins. But in other cases, the DNA itself is chemically modified. That changes how various proteins interact with it.