On May 15th, 2018 we learned about

Researchers use RNA to move memories between snails’ brains

On a practical level, our brains require experience to learn and remember new information. As far as scientists can tell, that information is encoded in a network of synapses, or the connections between brain cells, in various combinations. This structural aspect of memory seems to require that brain cells construct synapses themselves, negating any chance of having new memories being imprinted or injected into the brain all at once. However, researchers are investigating other forms of information found in the brain, focusing on RNA molecules inside brain cells, instead of the connections between those cells. This has opened up some intriguing possibilities, including the ability to transfer memories from one brain to another.

Purposes beyond building proteins

RNA is a complex protein structure that plays a number of roles in cell functionality. It’s most commonly associated with transferring instructions from a cell’s DNA to actual protein production, but researchers are realizing that that is only one of its jobs in the body. To see if it can carry information about an individual animal’s experiences, researchers tried gently scaring some snails to see if RNA could hold information from a memory as well.

The experiment started with marine snails called California sea hares (Aplysia californica) which were given small electric shocks. As the research lead Prof David Glanzman, made a point to specify, the shocks weren’t strong enough to cause harm the snails, and were really only meant to get them to feel the need to retreat from a physical stimulus. After a bit of “training,” zapped snails would retreat from a gentle poke for as long as 40 seconds, while untrained snails would pull back only for a moment.

Injecting information

Once that experience-dependent behavior was established, researchers extracted RNA from brain cells of both groups of snails. The RNA was then injected into the brains of a third batch of snails who had yet to be poked one way or the other. Snails receiving “unzapped” RNA didn’t really change their behavior, reacting only briefly to gentle pokes from researchers. Snails who received RNA from a zapped snail had a bigger response, retreating from physical stimuli as if they had been trained to avoid shocks themselves. The difference in the RNA donors’ experience seemed to control how the recipient snail reacted as if they’d formed a memory on their own.

This seems like a big step towards injectable knowledge, but nobody is about to pick up a new skill in moments quite yet. Other neuroscientists point out that while this study suggests a role for RNA in memory, it doesn’t rule out the importance of synapses. Also, since snails only have 20,000 brain cells, there’s a good chance that the cognitive demand of retreating from a shock isn’t exactly on par with how our brains’ 100 billion brain cells handle new data. Still, it seems that some kind of information was shared via neurons’ RNA, demonstrating a need for further investigation.


My third-grader-asked: Did the first snail that got zapped then forget it got zapped when they took out its RNA?

This wasn’t mentioned, although memory removal would certainly be an interesting wrinkle in a world of injectable information. However, since researchers probably weren’t targeting a single brain cell in the snail’s brain, some memory of being zapped would be left behind in other copies of that RNA memory, assuming that’s how this was all working in the first place.

There also didn’t seem to be a problem with choosing which cells should recieve the RNA injection in the recipient snails, indicating that the “memory” didn’t need to be added to one cell in particular. That may be thanks to the relative simplicity of a snail brain, or that RNA memories are rather general in scope. Maybe they actually trigger physiological responses more than encode details of a specific moment in a snail’s life?

Source: 'Memory transplant' achieved in snails by Shivani Dave, BBC News