RNA Moves a Memory From One Snail to Another

RNA Moves a Memory From One Snail to Another

RNA Moves a Memory From One Snail to Another

When the RNA was inserted into snails that had not undergone this process, they behaved just as if they had been sensitised.

Scientists have been able to transfer a memory from one snail to another, providing a tantalising clue to the answer of one of most vexing questions in biology - how are memories stored?

For decades, researchers have tried to pinpoint how, when, and where memories form.

The traditional view among neuroscientists is that memories are stored in our brain's synapses-the junctions between neurons, or nerve cells. Experiments in the 1960s, however, suggested RNA could play a role in making memories, though the work was largely written off as irreproducible.

"It's as though we transferred the memory", said the study's senior author, David Glanzman, from the University of California, Los Angeles.

David Glanzman tested the possibility that RNA from a trained California sea hare (Aplysia californica) can be used to create an engram - the elusive substrate of memory - in an untrained animal of the same species.

Previous studies point out that, after amnesia, long-term memory can be restored by using a priming component.

"It was completely arbitrary which synaptic connections got erased", Glanzman says. Scientists believe that in the future their method can be a tool to restore the memory of people with Alzheimer's disease.

The experiment also has quite major implications for our understanding of where our memories are stored.

The slugs have simple central nervous systems and large nerve cells that make experimental manipulation easier. Animals have developed a protective reflex, expressed in the contraction of the muscles during 50 seconds in subsequent contacts with the electrodes.

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. As for the snails, the team trained then beforehand to develop a defensive reaction to this procedure.

This idea is probably going to strike most of my colleagues as extremely improbable.

All seven of the snails that received the new RNA then went on to hide in their shells for an average of 40 seconds when the scientists came knocking, according to a paper published today in the journal eNeuro.

DNA methylation appeared to be essential for the transfer of the memory among snails.

Scientists extracted RNA from the nervous systems of the snails that received the shocks and injected it into a small number of marine snails that had not been sensitised in this way. When Glanzman repeated the experiment with RNA from sea snails that had been hooked up to wires but not shocked, the reflex behaviour did not transfer. Zapping the culture with a bit of current excited the sensory neurons much more than neurons treated with RNA from nonshocked snails.

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