A team successfully transplanted memories by transferring a form of genetic information called RNA from one snail into another. By repeatedly shocking the snail's tail, the animal learns to stay in that defensive position when touched on the siphon, even weeks after the shocks end. After that, they injected it into some marine snails that had not received the shocks.
The research that was published in the Journal eNeuro can now provide better ideas about the search for the physical basis of memory.
RNA, or ribonucleic acid, is a molecule present in virtually all organisms that acts as a biological messenger, carrying instructions from our genes to the rest of the cell.
The second group then received the shocks and the snails contracted for only about two seconds.
They then extracted RNA from the gastropods and injected them into a group of untrained snails, who behaved in a similar manner to the shocked animals by displaying a defensive contraction that lasted an average of about 40 seconds.
The shocked snails had been "sensitised" to the stimulus.
The RNA in the trained snail was used to create an engram - the elusive substrate of memory - by sensitising them with tail simulation that triggers an involuntary defensive reflex.
Professor David Glanzman, renowned author from the University of California, Los Angeles says that the result was as though they had transferred the memory itself from one snail to the other.
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"These are marine snails and when they are alarmed they release a handsome purple ink to hide themselves from predators". The team found that the snail synapses built to "store" a memory weren't necessarily the synapses that were removed from the neural circuits in the memory-erasing experiments.
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.
"If memories were stored at synapses, there is no way our experiment would have worked", said Glanzman, who added that the marine snail is an excellent model for studying the brain and memory.
The trained RNA also increased the excitability of cultured sensory neurons, obtained from untrained animals, which control this reflex all of which raises the possibility that RNA could be used to modify memory in other organisms, including us. 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.
Yes, sea snails may have 20,000 neurons - a paltry sum compared to humans' 100 billion.
"I think in the not-too-distant future, we could potentially use RNA to ameliorate the effects of Alzheimer's disease or post-traumatic stress disorder", he said.
When asked if this process would be conducive to the transplant of memories laid down through life experiences, Prof Glanzman was uncertain, but he expressed optimism that the greater understanding of memory storage would lead to a greater opportunity to explore different aspects of memory.