Most of us have trouble remembering our first grade teacher's name, or even what we had for breakfast this morning. This is natural — our long-term and short-term memory worsens with age, but why do we recall other events more vividly than others, and how can we improve our memory? Researchers at UT Southwestern Medical Center suggest the secret to creating long-lasting memories is to find something interesting enough that will activate chemicals in the brain to boost our recollection.

“In general, anything that will grab your attention in a persistent kind of way can lead to activation,” said Dr. Robert Greene, co-senior author of the study, and a Professor of Psychiatry and Neurosciences with the O’Donnell Brain Institute, in a statement.

Scientists have known dopamine — a chemical in the brain that affects movement, memory, and pleasurable reward — plays an influential role in memory enhancement. Dopamine released in the locus coeruleus (LC) region of the brain, which affects emotions, anxiety levels, sleep patterns, memory, and other aspects of behavior, can be naturally activated through behavioral actions, and these actions themselves can enhance memory retention. The degree to which these memories are enhanced is linked to the degree of activation.

People tend to remember certain events in their lives with particular clarity as well as unrelated details pertaining to the events. For example, they remember what they were doing in the hours before the Sept. 11, 2001, terrorist attacks. “When the New York World Trade Center came down on 9/11, that was high activation,” said Greene.

Inevitably, life-changing events trigger the release of dopamine in the LC, but Greene and his colleagues suggest playing a new video game or doing a novel activity after studying for an exam, or memorizing a big speech, could lead to better long-term memory.

In the study published in the journal Nature, the researchers sought to establish a link between LC neurons and neuronal circuits in the hippocampus — the region of the brain responsible for recording memories — that receive dopamine from the LC in 120 mice. The mice were put in an arena to search for food hidden in sand that changed location for each study. Giving the mice a "novel experience," such as exploring an unfamiliar floor surface 30 minutes after being trained to remember the food location, boosted memory retention when it came to finding the food the next day.

In the second part of the study, the researchers injected the mice with a genetically encoded light-sensitive activator called channelrhodopsin. The sensor would allow them to selectively activate dopamine-carrying neurons of the LC that go to the hippocampus to see what neurons were responsible for memory enhancement. Here, selectively activating the channelrhodopsin-labeled neurons with blue light (optogenetics) substituted the novelty experience as a memory enhancer for mice. This activation also led to a direct, long-lasting synaptic strengthening — an enhancement of memory-relevant communication occurring at the junctions between neurons in the hippocampus, according to the researchers.

It is the attention-grabbing experiences that trigger the release of memory-enhances chemicals. They are able to embed these memories into our psyche just before or soon after the experience, whether or not they're related to the event. In other words, the researchers were able to use optogenetics to design a novel experience to boost the mice's memory retention.

Similar studies have found unique ways to clear up cognitive fog. For example, a 2002 study in the journal Appetite found gum-chewers performed significantly better on tests of both long-term and short-term memory than did empty-mouthed people. Although scientists are still trying to figure out why that's the case, they hypothesize chewing gum affects the function of the hippocampus by causing the body to release insulin in preparation for food.

Greene and his colleagues have yet to determine how big of an influence their discovery might have on human learning, whether it could lead to an understanding of how patients' memories fail, or how to find better therapies for these patients.

Until then, chewing a piece of bubblegum can't hurt.

Source: Takeuchi T, Duszkiewicz AJ, Sonneborn A et al. Locus coeruleus and dopaminergic consolidation of everyday memory. Nature. 2016.