Researchers have successfully transferred a sea snail's memory to another one by injecting RNA from a trained sea snail into an untrained one. After around 24 hours the snails had developed an instinctual reaction to recoil when being tapped on the tail.
The scientists injected the RNA from the sensitized group into seven snails that had not received any shocks.
The "memory transplant" was achieved through ribonucleic acid (RNA) injections and provides new tantalizing clues regarding the memory trace - also known as an engram, the presumed physical substrate of memory. They used small electric shocks to sea sails called Aplysia californica. When the researchers tapped these snails, their defensive contractions lasted 40 seconds, even though that had never been sensitized.
Results showed that the untrained snails that received RNA from trained snails had the same response to taps as if they were shocked, and contracted for nearly 40 seconds. RNA from shocked snails also enhanced a subset of synapses between sensory and motor neurons in vitro, suggesting it was indeed the RNA that transported the memory, Glanzman explains. Extracting RNA from these trained animals and injecting it into untrained animals resulted in a similar sensitized response.
The snails in one group were trained to respond to a stimulus - a mild election shock on the tail - which triggered a defensive withdraw reflex.
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"These are marine snails and when they are alarmed they release a lovely purple ink to hide themselves from predators". They had, in essence, transferred the fear of being shocked. The long-term memories are considered to be stored at the synapses of the brain or the junctions between the nerve cells. Each neuron has several thousand synapses. The memory is not stored in the RNA itself, he speculates-instead, noncoding RNA produces epigenetic changes in the nucleus of neurons, thereby storing the memory.
This raises the possibility that RNA plays an important role in memory formation - an idea that some previous studies using the same species of snail seems to support.
The type of RNA relevant to these findings is believed to regulate a variety functions in the cell involved with the development and disease. But despite the vast difference, the researchers said the cells of marine snails are still similar to those of humans, which makes this discovery that much more significant.
They see this advancement as a step towards helping to get rid of the effects of diseases such as Alzheimer's or Post Traumatic Stress Disorder (PTSD).
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.