"If we go back to the early 1900s, this is when the idea was first proposed that memories are physically stored in some location within the brain," says Michael R. Williamson, a researcher at the Baylor College of Medicine in Houston. For a long time, neuroscientists thought that the storage of memory in the brain was the job of engrams, ensembles of neurons that activate during a learning event. But it turned out this wasn't the whole picture.

Williamson's research investigated the role astrocytes, non-neuron brain cells, play in the read-and-write operations that go on in our heads. "Over the last 20 years the role of astrocytes has been understood better. We've learned that they can activate neurons. The addition we have made to that is showing that there are subsets of astrocytes that are active and involved in storing specific memories," Williamson says in describing a new study his lab has published.

One consequence of this finding: Astrocytes could be artificially manipulated to suppress or enhance a specific memory, leaving all other memories intact.

Astrocytes, otherwise known as star cells due to their shape, play various roles in the brain, and many are focused on the health and activity of their neighboring neurons. Williamson's team started by developing techniques that enabled them to mark chosen ensembles of astrocytes to see when they activate genes (including one named c-Fos) that help neurons reconfigure their connections and are deemed crucial for memory formation. This was based on the idea that the same pathway would be active in neurons and astrocytes.