Grow a New Head for Old Memories

In fairly unnerving science news, the Smithsonian reports that flatworms retain old knowledge and training even after being decapitated.

The researchers, Tal Shomrat and Michael Levin, trained flatworms to travel across a rough surface to access food, then removed their heads. Two weeks later, after the heads grew back, the worms somehow regained their tendency to navigate across rough terrain.

The study was simple: the researchers conditioned two sets of 72 worms each to expect food from either a rough-bottomed or smooth-bottomed dish. Then, they put each set of worms into a rough-bottomed dish with one quadrant filled with food (which the worms like) and blue LED light (which the worms don’t). The worms which had previously lived in a rough-bottomed dish took significantly less time to approach the food than the worms who’d lived on smooth surfaces.

Afterward, all worms were fully decapitated (every bit of brain was removed) and left alone to regrow their heads over the course of the next two weeks. When they were put back in the chamber with the rough surface, the group that had previously lived in the rough dishes — that is, their previous heads had lived in the rough dishes — were still willing to venture into the lit quadrant of the rough dish and spend an extended period of time there more than a minute faster than the other group.

“Their previous heads.” The Smithsonian article also covers a now-mostly-discredited study from half a century ago, one that arrived at a similar (but methodologically much creepier) conclusion:

Interest in flatworm memories dates to the 1950s, when a series of strange experiments by Michigan biologist James McConnell indicated that worms could gain the ability to navigate a maze by being fed the ground-up remains of other flatworms that had been trained to run through the same maze. McConnell speculated that a type of genetic material called “memory RNA” was responsible for this phenomenon, and could be transferred between the organisms.