An innovative method for improving memory during sleep was recently discovered. This new intervention could potentially restore memory capabilities following brain injuries, or assist treatment of patients with post-traumatic stress disorder (PTSD).
Researchers at Tel Aviv University and the Weizmann Institute of Science have found a method that relies on a memory-evoking scent administered to one nostril. Their findings were recently published in the journal Current Biology.
Memory consolidation is a process that occurs in the brain during sleep. New memories begin as short-term memory and are stored in a region of the brain called the hippocampus. The hippocampus is a deeply embedded structure in the temporal lobe and its name is derived from the Greek word for “seahorse,” which the structure loosely resembles. The memories gradually transition from this temporary cache to various regions of the cerebral cortex for long-term memory storage. How this transition actually occurs has eluded scientists for years.
Our current knowledge reveals that memories associated with physical locations on the left side of a person are primarily stored in the right brain hemisphere and locations on the right side being stored in the left brain. The investigators then proceeded to expose the research participants to the scent of a rose while they were asked to remember the location of words presented on either the left or right side of a computer screen. The participants were then tested on their recall of the word locations, after which they proceeded to take a short nap in the lab. During their nap, the rose scent was administered again, but this time to only one nostril. With the odor being delivered to only a single nostril, the researchers were able to improve recall and consolidate specific memories that were stored in the specific brain hemisphere side opposite the nostril receiving the scent (i.e., left nostril, right brain; right nostril, left brain)
Electrical brain activity was recorded during sleep with electroencephalography (EEG). The results of the EEG were significant for different sleep wave patterns in the two hemispheres following “one-sided” odor administration. The hemisphere that received the scent (which would be opposite the nostril receiving the scent) revealed electrical signatures representing improved memory consolidation during sleep.
The last test was performed after the subjects woke. They underwent a second recall test for the words memorized prior to falling asleep. The subject’s memories were significantly better for words presented on the side affected by smell than the words presented on the other side.
Their findings reveal that long-term memory consolidation can be assisted by external cues such as scents or smells. Although further clinical study is needed, memories can potentially be manipulated with scents and smells by intervening in the nocturnal communications between the hippocampus and regions in the cerebral cortex.
While the exact pathway from short-term memory formation to long-term memory consolidation continues to evade scientists, we now know that smell seems to improve or strengthen this process. Many of us have experienced the exceptional power of scents and smells on memory, like the potent antiseptic smell of a hospital where your baby was born, the deep and rich smell of a French restaurant where you proposed to your spouse, or the melange of body odors present on the homeless man who happens to also be your first emergency room patient. Scents and smells can powerfully evoke these life-changing memories.
In addition to furthering our understanding of how sleep aids memory formation, the researchers anticipate potential clinical applications from this method in the future. This method could be particularly helpful for patients with PTSD, where memory can serve as a strong emotional trigger as well as assisting the rehabilitation process after cerebrovascular accidents or strokes. The vast majority of strokes result in one-sided brain damage.
In the technocratic, digital age of today, less and less emphasis seems to be placed on curating our own memories. After decades of using an appeal to fear (fear of lost memories), the tech industry has successfully convinced most of us to outsource our memories to technology. We now have hard drives and servers full of phone numbers, shopping lists, photos, and videos. That’s great, but it will never replace the depth of detail from a strong memory composed of all the five senses.
In addition to the obvious memory aids of adequate sleep, paying attention, and reflecting on your day, we can now add scent and smell therapy to the list. So the next time there is that special occasion you want to never forget, cook a pungent meal, bring some flowers, or just light a candle. The smell will help you remember.
Armen Nikogosian, M.D., practices functional and integrative medicine at Southwest Functional Medicine in Henderson, Nev. He is board-certified in internal medicine and a member of the Institute for Functional Medicine and the Medical Academy of Pediatric Special Needs. His practice focuses on the treatment of complex medical conditions with a special emphasis on autism spectrum disorder in children, as well as chronic gut issues and autoimmune conditions in adults.