With RNA, Researchers Transfer Memories Between Sea Slugs

Spencer Underwood
May 16, 2018

Researchers have successfully transferred a sea snail's memory to another one by injecting RNA from a trained sea snail into an untrained one.

They noted that the snails that had received the shocks performed a defensive reflex for about 50 seconds when tapped, while other snails contracted for just one second.

Glanzman wanted to know if the RNA from shocked snails actually affected the neuronal connections of the snails receiving the injections any differently than RNA from nonshocked snails.

When touched lightly on the siphon, the neurons fire, retract the tissue, and contract the gill within the body cavity for a few seconds to protect it against attack. Siphons are tube-like structures in molluscs in which water flows.

Researchers say that his experiment shows how essential parts of the memory trace or engram can be. They chose to see whether something beyond the brain cells' connections to each other - namely, RNA - could be hanging on to the memory. Then later, the researchers reactivated those tagged neurons in order to fiddle with whatever memory the cells were involved in.

Tsai, who recently co-authored a major review on memory formation, called Glanzman's study "impressive and interesting" and said a number of studies support the notion that epigenetic mechanisms play some role in memory formation, which is likely a complex and multifaceted process. Glanzman said about the results, "It's as if we transferred a memory".

More tests in petri dishes showed that the RNA from trained snails showed that their sensory neurons were more excited than the ones of the untrained snails. The team's research is published May 14 in eNeuro, the online journal of the Society for Neuroscience.


Dr. Todd Sacktor, a neurologist from SUNY Downstate Medical Center told Scientific American that this memory transfer was shocking.

The study suggests some memories may be stored in genetic code, at least in animals, Live Science said.

Other scientists are dubious about the work.

Tomás Ryan, who studies memory at Trinity College Dublin, is firmly unconvinced. The memory of the trained cells appeared to have been transferred to the untrained ones.

"If memories were stored at synapses, there is no way our experiment would have worked". Short term memories are stored in the pre-fontal lobe. The hippocampus is able to string various simultaneous memories into a single memory.

The current favoured theory among neuroscientists, however, is that long-term memories are encoded in synapses - the functional interfaces between neurons through which electrical or chemical signals pass. Experts are sceptical about the research though because the brains of the slugs are much simpler in comparison to higher animals and humans and it could be a distant possibility to imagine same could be done for humans.

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