Scientists have successfully transferred a memory from one marine snail to another - but there's still a long way to go until you can pay someone to wipe unpleasant memories or implant new ones a la Total Recall, or Eternal Sunshine of the Spotless Mind.
Clearly, it's a long way from making you believe you'd spent two weeks on another planet, but the possibility of scientists helping you "remember" something you'd never done before is real.
"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", said David Glanzman, senior author of the study and a UCLA professor of integrative biology and physiology and of neurobiology. See, some researchers think memories are stored in the synapses (the spaces between nerve cells).
"It was completely arbitrary which synaptic connections got erased", Glanzman says. Specifically, how memories are stored.
Glanzman turned his attention to RNA because of those earlier hints it was related to memory, and also because of recent experiments suggesting long-term memory was stored in the cell bodies of neurons, not synapses. The results provide support for a nonsynaptic, epigenetic model of memory storage in Aplysia. Like all mollusks, these snails have groups of neurons called ganglia, rather than brains.
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.
Meanwhile, the untrained snails who had received RNA from untrained donors did not exhibit any change in their defensive response. 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. Snails in the control group, which biologists did not cause sensitisation, duration of the reaction to the current was one second.
In comparison, snails tapped without electricity retreated for an average of 10 seconds.
DNA methylation appeared to be essential for the transfer of the memory among snails.
For the experiment, the researchers gathered a number of marine snails (known as Aplysia) and gave them mild electric shocks.
For the next step, RNA was extracted from both the trained and untrained snails.
For the next stage of the experiment, the researchers extracted motor neurons and sensory neurons from untrained snails, putting them in petri dishes either separately or in pairs containing one neuron of each type.
When a marine snail is given electric tail shocks, its sensory neurons become more excitable. However, Glanzman explained this would contradict his findings.