To most people, a memory transplant may sound like a science fiction trope at best. But researchers from the University of California, Los Angeles (UCLA) have successfully transferred memories between snails for the first time. Though it is too early to be sure, findings from the experiment might even challenge how experts have understood storage of memories in the brain.

The study titled "RNA from Trained Aplysia Can Induce an Epigenetic Engram for Long-Term Sensitization in Untrained Aplysia" was published in the journal eNeuro on May 14.

Ribonucleic acid (RNA) is a molecule that plays an important role in gene expression, assembly of proteins, and cellular processes involved in development and disease. It is responsible for carrying instructions from the deoxyribonucleic acid or DNA to other parts of the cell.

For the experiment, the researchers gathered a number of marine snails (known as Aplysia) and gave them mild electric shocks. They received one shock every 20 minutes, five times in a row followed by five more after 24 hours. These shocks were said to enhance the withdrawal reflex of the snail, a defensive contraction it displays to protect itself from a potential threat.

The researchers noted the snails given the shocks displayed a defensive contraction that lasted an average of 50 seconds (known as sensitization) while those that were not given the shocks contracted for only about one second.

For the next part of the experiment, the researchers extracted RNA from the sensitized snails (the ones given shocks) and injected it into seven snails that had not received any shocks. The seven snails reacted as though they had received the tail shocks by displaying a defensive contraction of about 40 seconds. 

The result was "as though we transferred the memory," according to senior author David Glanzman, a professor of integrative biology and physiology and of neurobiology at UCLA.

"These are marine snails and when they are alarmed they release a beautiful purple ink to hide themselves from predators. So these snails are alarmed and release ink, but they aren't physically damaged by the shocks," he said.

Marine snails were chosen for the experiment as their cellular and molecular processes are quite similar to that of human beings. Despite the similarities, a snail has only about 20,000 neurons (nerve cells) in its central nervous system compared to the human nervous system, which has about a 100 billion.

Each neuron in our brain contains several thousand synapses, which is where memories were believed to be stored. However, Glanzman explained this would contradict his findings. 

"If memories were stored at synapses, there is no way our experiment would have worked," he said, leading him to believe memories are actually stored in the nucleus of neurons. 

Given that there are different kinds of RNA, Glanzman hoped to take up further research aimed at identifying which types of RNA that can be used to transfer memories. 

"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 stated.