A Scent-sational Memory Boost

Art Courtesy of Angelique Rouen.

Crying over a textbook with exams approaching? Can’t remember the name of that familiar face? The solution may lie right under your nose—literally.

In a paper published in the Frontiers of Neuroscience, scientists at the University of California, Irvine (UCI) found that the cognitive capacity of older adults increased by a whopping 226 percent when exposed to a different fragrance every night for six months. Participants of the study simply placed one of seven different essential oil scents—eucalyptus, lavender, lemon, orange, peppermint, rose, and rosemary—into a two-hour diffuser each night to reap the benefits of improved memory. By stimulating the neural networks in the brain with uncommon odors, the researchers found that the critical memory pathways of participants were significantly strengthened along with memory test scores when compared to the control group. 

The association between olfactory stimulation and memory has, in fact, long been established. For example, young adults who have trained as sommeliers—and have therefore been exposed to dozens of wine odors every day for months—have thicker brains, specifically in the entorhinal cortex, an area heavily associated with memory capacity. Another more recent example is the loss of smell as a result of COVID-19, which can lead to symptoms of poor memory and ‘brain fog.’ However, the most remarkable example of the relationship between smell and memory was demonstrated in South Korea where dementia patients were exposed to forty odors twice a day, resulting in a 300 percent memory improvement compared to other dementia patients who did not receive this olfactory stimulation. So, what sets the new UCI study apart?

“We’ve automated the process of olfactory enrichment. After all, it’s unrealistic for patients to open forty bottles of perfume and sniff each one every day,” said Michael Leon, Professor of Neurobiology and Behavior at UCI and a co-author of the paper. “The advantage of using odors at night is that odors can’t wake you up. Unlike other sensory systems, the olfactory system doesn’t go through the thalamus, which is connected to the sleep centers. You can wake somebody up with a noise or bright light or by touching them, but you can’t wake somebody up with an odor, even if the odor is of frying bacon.”

While many people may be familiar with aromatherapy, in which scents from an essential oil are used for therapeutic purposes, “olfactory enrichment” is a distinct concept. The benefit does not come from one particular scent—instead, olfactory enrichment is reliant on long-term exposure to a multitude of new scents to stimulate the nervous system.

Leon’s team has now constructed a diffuser device capable of automatically delivering forty odors at night, aptly named MemoryAir. But wouldn’t the novelty of these scents wear off?

“No,” Leon answered. “It turns out that people are not very good at identifying odors, let alone forty of them. So people will get that novel experience even if they do it over the course of many months. Although, we do have plans to introduce new odors in the future.” 

From their research, Leon and his partners are optimistic about the wider implications of their work for the treatment of dementia patients and for society at large.

“We believe everybody in the modern affluent world is chronically deprived of olfactory stimulation. In fact, if you take a deep breath now, you probably wouldn’t smell anything at all,” Leon said. “The human brain evolved at a time when there were plenty of odors around. So, the good thing about being in the affluent world is that you don’t have a lot of odors. The bad thing about not having a lot of odors is that your brain is deteriorating or at least not fulfilling its full potential because it doesn’t get that stimulation.”

While the long-term effects of our odorless modern life remain a mystery, Leon argues that olfactory enrichment may be a simple and inexpensive tool for the prevention and treatment of dementia. But first, this technology needs to be tested on a larger pool of patients—particularly those diagnosed with dementia. Additionally, there were concerns about the small size of the study group since some participants were removed to limit confounding factors that the COVID-19 pandemic may have introduced. 

Even so, the next time you’re grinding for your next exam past midnight, remember that novel scents—both pleasant and unpleasant—may boost your memory.