Learning new things would be so much easier if we could just download them into our brains, like in The Matrix. Now, biologists at the University of California, Los Angeles (UCLA) have pulled off something similar – at least on a gastropod level – by effectively transferring a memory from a trained snail into the mind of an untrained one. The experiment could eventually lead to new treatments for restoring memory in Alzheimer's patients or to reduce traumatic memories.
The researchers studied a species of marine snail known as Aplysia. These are commonly used as animal models for neuroscience because the cellular and molecular processes at work are relatively similar to humans, but they have a far more manageable number of neurons – about 20,000, compared to our 100 billion.
In their experiments, the UCLA researchers trained snails to be more sensitive to perceived danger. This was done by giving them five mild electric shocks to their tails, 20 minutes apart, and then repeating the process 24 hours later. That makes the animals more sensitive, so that in response to stimuli they defensively withdraw for longer than they normally would. The team found that the snails would withdraw for about 50 seconds on average, while a control group that hadn't received shocks would only contract for around one second.
The team wanted to test whether they could transfer "memories" to make untrained snails react the same way as the trained ones. To do so, they extracted RNA from the nervous systems of sensitized snails, and injected it into seven snails that hadn't received shocks. All seven of these snails reacted to stimuli in the same way as the trained snails, contracting for about 40 seconds on average.
"It's as though we transferred the memory," says David Glanzman, senior author of the study.
In the interest of removing as many variables as possible, they also extracted RNA from unshocked snails and injected it into other unshocked snails. Unsurprisingly, this control group showed no signs of sensitization.
The team then conducted the same experiment in Petri dishes. RNA from shocked and unshocked snails were added to Petri dishes containing unshocked snail neurons. They found that the shocked snail RNA made the in vitro sensory neurons more excitable, but the effect didn't carry across to motor neurons. And of course, the unshocked snail RNA had no effect on neurons at all.
The researchers say the experiment suggests that memories aren't stored in synapses, as is commonly believed, but may be stored in the nucleus of neurons.
"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," says Glanzman.
The research was published in the journal eNeuro.
Source: UCLA