A team of researchers tested the current theory that long-term memory is stored within modified connections between brain cells.
Their findings, published Monday in the journal eNeuro, challenge this premise and support recent evidence that suggests memory storage involves adjustments in gene expression induced by non-coding ribonucleic acids (RNAs) – which are not involved in protein coding.
“The significance is twofold,” co-author David Glanzman, a professor at the University of California, Los Angeles, told Courthouse News. “First, the standard idea regarding the cellular mechanism of memory storage holds that long-term memories are stored at synapses. Our results appear to contradict this idea.”
A synapse is the point at which a nerve impulse passes between neurons.
“Second, if our results prove general to other animals, particularly mammals, and to other forms of learning, the findings may lead to novel, more effective treatments of memory-related disorders, such as dementia and post-traumatic stress disorder,” he added.
Glanzman tested whether RNA from a trained California sea hare (Aplysia californica) can be used to form an engram – a hypothetical permanent change in the brain accounting for the existence of memory – in an untrained animal of the same species.
The team sensitized some snails with tail stimulation that fosters an involuntary defensive reflex. Extracting RNA from these trained animals and administering it into untrained animals led to a similar sensitized response.
The trained RNA also heightened the excitability of cultured sensory neurons, drawn from untrained animals, which control this response.
Researchers must now determine which type of RNA is involved in memory transfer.
“The next step is to sequence the RNA from the trained animals and the RNA from the untrained animals in order to determine the specific species of RNA that transmit the memory,” Glanzman said.
The research was funded by the National Institutes of Health’s National Institute of Neurological Disorders and Stroke and National Institute of Mental Health, as well as the National Science Foundation, and the Fyssen Foundation.