'Memory transplant' achieved in snails
'Memory transplant' achieved in snails
Despite the obvious differences, there are similarities
between the way that snail nerve cells function and the way that human cells
work
By Shivani Dave Reporter, BBC News May 14, 2018
Memory transfer has been at the heart of science fiction
for decades, but it's becoming more like science fact.
A team successfully transplanted memories by transferring
a form of genetic information called RNA from one snail into another.
The snails were trained to develop a defensive reaction.
When the RNA was inserted into snails that had not
undergone this process, they behaved just as if they had been sensitised.
The research, published in the journal eNeuro, could
provide new clues in the search for the physical basis of memory.
RNA stands for ribonucleic acid; it's a large molecule
involved in various essential roles within biological organisms - including the
assembly of proteins and the way that genes are expressed more generally.
The scientists gave mild electric shocks to the tails of
a species of marine snail called Aplysia californica. After these shocks were
administered. the snail's defensive withdrawal reflex - where the snails
contract in order to protect themselves from harm.
When the researchers subsequently tapped the snails, they
found those that had been given the shocks displayed a defensive contraction
lasting about 50 seconds, while those that had not received the shocks
contracted for only about one second.
The shocked snails had been "sensitised" to the
stimulus.
Purple ink
Scientists extracted RNA from the nervous systems of the
snails that received the shocks and injected it into a small number of marine
snails that had not been sensitised in this way.
The non-sensitised snails injected with the RNA from the
shocked animals behaved as if they had themselves received the tail shocks,
displaying a defensive contraction of about 40 seconds.
They saw a similar effect when they did the same thing to
sensory nerve cells being studied in petri dishes.
Prof David Glanzman, one of the authors, from the
University of California, Los Angeles (UCLA), said the result was "as
though we transferred the memory".
He also stressed that the snails did not get hurt:
"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.
Traditionally, long-term memories were thought to be
stored at the brain's synapses, the junctions between nerve cells. Each neuron
has several thousand synapses.
But Prof Glanzman said: "If memories were stored at
synapses, there is no way our experiment would have worked."
The UCLA professor of integrative biology holds a
different view, believing that memories are stored in the nuclei of neurons.
The paper might support hints from studies conducted decades ago that RNA was
involved in memory.
The type of RNA relevant to these findings is believed to
regulate a variety functions in the cell involved with the development and
disease.
The researchers said that the cells and molecular
processes in the marine snails are similar to those in humans, despite the fact
that the snail has about 20,000 neurons in its central nervous system and humans
are thought to have about 100 billion.
The researchers see this result as a step towards
alleviating 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.
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