The Importance of Smell and Sleep on Memory

    Olfaction, also known as smell, been seen to be an effective way of provoking memories but have you ever thought that olfaction and sleep can have an effect on your memory consolidation? Laura K Shanahan and colleagues were interested in this phenomenon. In their research, they explored the ways in which smell and sleep influence memory consolidation. In their research article “Scents and Reminiscence: Olfactory Influences on Memory Consolidation in the Sleeping Human Brain”, these researchers explained how smell has been proven to be an effective stimulus in the reactivation of memories during sleep in humans. They explain that this phenomenon occurs because the olfactory pathway leads directly into the limbic network that supports memory and emotion. In order to observe this phenomenon, researchers asked participants to learn the locations of card pairs. In this visuospatial task, a rose odor was also paired in their environment. Once the locations of the card pairs were learned, the participants went to sleep. While asleep either the same rose odor or a control odor was presented. When the participants awoke, they were asked to recall the locations of the paired cards that they previously learned prior to falling asleep. Results indicated that those who were exposed to the rose odor before falling asleep and while they were asleep performed better on the memory test than those who were exposed to the control odor when they slept. 

Another study similar to Dr. Shanahan's experiment also investigates the role of smell, memory, and sleep and how it specifically impacts the test performance of German students in an English class. Dr. Franziska Neumann and colleagues in their paper, “How odor cues help to optimize learning during sleep in a real-life setting” were also interested in the associations between olfaction and memory and how it can potentially be used to enhanced learning abilities in students. In this study, 54 German sixth-grade participants were split into four experimental groups. Group 1 had no exposure to odor cues. Group 2 had exposure to a rose scent while learning English vocabulary words as well as had exposure to the rose scent while taking the vocabulary test. Group 3 had exposure to the rose scent while learning the English vocabulary at home and during each night before the test but not during the test. Group 4 had exposure to the rose scent while learning at home, as well as every night before the test and during the test. Results indicated that participants in groups 3 and 4 performed increasingly better than those in the other groups. 

    Just like Dr. Shanahan’s study, Dr. Neumann's study indicated that exposure to aromas before, while asleep and during a specific task increased memory performance on humans. Both experiments also showed how we can apply this scientific discovery to real-life scenarios. For example, this may be a new study technique that teachers may present to their students upon taking an exam to enhance their memory on the topic of study. This may even be important in a clinical setting when working with patients with Dementia and Alzheimer's. With more research, this can potentially be used on those who are diagnosed early with Alzheimer's and Dementia because it can possibly be used as a preventive measure and be able to preserve their memory. 

Shanahan, L.K., & Gottfried, J. (2017). Scents and Reminiscence: Olfactory Influences on Memory Consolidation in the Sleeping Human Brain.

Neumann, F., Oberhauser, V., & Kornmeier, J. (2020). How odor cues help to optimize learning during sleep in a real-life setting.