At Glanzman's lab, researchers administered a series of mild electric shocks to the tails of a marine snail known as the Aplysia californica. Then later, the researchers reactivated those tagged neurons in order to fiddle with whatever memory the cells were involved in. In the 1940s, Canadian psychologist Donald Hebb proposed memories are made in the connections between neurons, called synapses, and stored as those connections grow stronger and more abundant.
Researchers also extracted RNA from snails that had not received any shocks, and transferred it to another group of snails that also had not been shocked.
Traditionally, long-term memories were thought to be stored at the brain's synapses, the junctions between nerve cells. In the snail's gut, for example, are specific sensory and motor neurons that control the withdrawal of a fleshy, spout-like organ on the snail's back called a siphon and the contraction of a caterpillar-looking gill, which the animal uses to breathe.
Next, the team took some ribonucleic acid (RNA), which forms proteins based on cells' DNA, from nerve tissue in the upper abdomen of trained snails and injected it into the untrained snails' necks to get to their circulatory system. The paper might support hints from studies conducted decades ago that RNA was involved in memory. He says that researchers are still trying to work out the way of how memories are stored. A group of untrained snails received RNA from the trained group and the second group received RNA from an untrained group.
The experiment revealed that the recipients of the "memory transplant" contracted for about 40 seconds when tapped, suggesting that the RNA injections had transferred the memory of the electric shock to the unsensitized snails.
"It was as though we transferred the memory", Glanzman said in a press release. After around 24 hours the snails had developed an instinctual reaction to recoil when being tapped on the tail. But scientists have gradually realized that there is more to RNA than playing messenger. This produced "increased excitability" in the neurons, according to the UCLA statement, whereas RNA from un-shocked snails did not.
The idea "seems quite radical as we don't have a specific mechanism for how it works in a non-synaptic manner", Bong-Kiun Kaang, a neuroscientist at Seoul National University who was not involved in the study, writes in an email to The Scientist. Experimental creatures became sea snail.
As Glanzman points out, if that theory were true, then the experiment wouldn't have succeeded.
But there are many different types of RNA, and Glanzman's team plans to do more research to figure out determine which types most directly impact memory. "But if we're right, we're just at the beginning of understanding how memory works".