In a new study conducted on unsuspecting mice, Swedish researchers at the medical university Karolinska Institutet managed to accomplish a major breakthrough in the field of neuroscience, when they identified a mechanism related to the formation of long-term memories. Their find essentially controls the brain's ability to store information for longer than a few seconds; and the new-found knowledge is bound to have considerable implications for the field of medicine today. Details of the discovery appear in the latest issue of the journal Proceedings of the National Academy of Sciences.

“We are constantly being swamped with sensory impression. After a while, the brain must decide what's to be stored long term. It's this mechanism for how the connections between nerve fibers are altered so as to store selected memories that we've been able to describe,” explains the leader of the new study, professor Lars Olson. In the experiments, the Swedish team was able to control mice's ability to form long-lasting memories by simply adding or subtracting a substance from the water.

Converting sensory impression into memory is the very essence of our ability to learn. Data about past experiences is maintained in the brain in such a way that it allows for its most important part to be accessed at all times. Until now, the only stage of memory formation that was made relatively clear was the first one, in which new memories only last for a few hours. After that time, changes in synapses – the connections between neurons – alter the data, and render it useless for conscious use. The real cherry on the cake for researchers was to identify how synapses change when long-term memories form.

Following their investigation, the Karolinska Institutet team managed to find out that the nogo receptor 1 (NgR1), a receptor molecule, had an important role in cellular membrane signaling, a process that was essential to storing long-term memories in the cerebral cortex, AlphaGalileo reports. When nerve cells are active, Olson says, NgR1 is inactivated. The team hypothesized that this might be essential to memory formation, and proceeded toward creating mice that expressed the receptor molecule even when they normally shouldn't have.

“Doing this, we found that the ability to retain something in the memory for the first 24 hours was normal in the genetically modified mice. However, two different memory tests showed that the mice had serious difficulties converting their normal short-term memories to long-term ones, the kind that last for months,” Olson reveals.

“We know that concussion can cause someone to forget events that occurred in the week before the injury, what we call retrograde amnesia, even though they can remember events that occurred earlier than about a week before. This we believe tallies with our findings,” concludes study scientist Alexandra Karlen.