'Memories' Transferred From One Snail to Another Via Injection, Scientists Say
Scientists have transferred "memories" from one group of snails to another via injection, according to a new study published in the online journal eNeuro.
For the study, researchers from the University of California Los Angeles administered a series of mild electric shocks to marine snails from a species called Aplysia. These shocks amplified the snails' defensive withdrawal reflex—which it uses to protect itself. This simple form of learning is known as "sensitization."
This amplification was demonstrated by the fact that after the shocks were administered, the snails' defensive contractions lasted around 50 seconds on average when the scientists tapped their shells. Normally, these snails only contract for one second.
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).
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 scientists injected the RNA from the sensitized group into seven snails that had not received any shocks. And, as a comparison, they took the RNA from the unsensitized snails and injected it into a control group of seven other snails that had also not received any shocks.
Intriguingly, the scientists found that the seven snails that received the RNA from the sensitized group began to behave as if they had been shocked. When the researchers tapped these snails, their defensive contractions lasted 40 seconds, even though that had never been sensitized. The snails in the control group did not display this behavior, indicating that the injection was responsible.
"It's as though we transferred the memory," said David Glanzman, a professor of integrative biology and physiology and of neurobiology at UCLA, and senior author of the study, said in a statement.
The new findings could one day help to restore lost memories or reduce the trauma of painful memories, according to the researchers.
"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," Glanzman said.
The traditional view among neuroscientists is that memories are stored in our brain's synapses—the junctions between neurons, or nerve cells. Glanzman, however, thinks that these memories are actually stored in the nuclei of neurons.
"If memories were stored at synapses, there is no way our experiment would have worked," he said.
Glanzman and his colleagues published research in 2014 suggesting that lost memories could potentially be restored based on this concept.
Marine snails were used in the experiment because they are an excellent model for studying the brain and memory. Despite the fact that they only have around 20,000 neurons in comparison to the 100 billion in humans, the cellular and molecular processes in their brains appear to be very similar. Researchers also know more about the biology of sensitization in marine snails than any other animal.
