Published: Tue, May 15, 2018
Medicine | By Brett Sutton

Scientists successfully transfer memory from one snail to another

Scientists successfully transfer memory from one snail to another

If confirmed in other species, the finding may lead to a shift in scientists' thinking about how memories are made-rather than cemented in nerve-cell connections, they may be spurred on by RNA-induced epigenetic changes.

The "memory transplant" was achieved through ribonucleic acid (RNA) injections and provides new tantalizing clues regarding the memory trace - also known as an engram, the presumed physical substrate of memory. RNAs are effectively the messenger that carry out the instructions coded into our DNA. It is now understood to have other important functions besides protein coding, including regulation of a variety of cellular processes involved in development and disease. They used small electric shocks to sea sails called Aplysia californica. After around 24 hours the snails had developed an instinctual reaction to recoil when being tapped on the tail.

Then, when scientists gave those marine molluscs a light knock, they withdrew into their shells in defence for 50 seconds. At first, the snails would only curl for a few seconds. Extracting RNA from these trained animals and injecting it into untrained animals resulted in a similar sensitized response.

Next, the researchers extracted a type of genetic material known as RNA from the nervous systems of the snails that had received the shock (the sensitized group), as well as from snails that had not received any shocks (an unsensitized group).

Remarkably, the scientists found that the seven that received the RNA from snails that were given the shocks behaved as if they themselves had received the tail shocks: They displayed a defensive contraction that lasted an average of about 40 seconds. Some dishes had RNA from marine snails that had been given electric tail shocks, and some dishes contained RNA from snails that had not been given shocks.

Glanzman said the next step in this research is to transfer RNA in more complex animals, like mice. The trained RNA also increased the excitability of cultured sensory neurons, obtained from untrained animals, which control this reflex.

But Professor Glanzman thinks memories are stored in the neurons, thousands of which make up each synapse.

He also stressed that the snails did not get hurt: "These are marine snails and when they are alarmed they release a lovely purple ink to hide themselves from predators".

The researchers said that the cells and molecular processes in the marine snails are similar to those in humans, despite the fact that the snail has about 20,000 neurons in its central nervous system and humans are thought to have about 100 billion. Seralynne Vann from Cardiff University in the United Kingdom made an interesting point about the chances of applying a similar technique in the study of human memory.

Glanzman and his colleagues published research in 2014 suggesting that lost memories could potentially be restored based on this concept.

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