Smells like memory
Sleep is essential for saving new memories. Scientists found a natural way to enhance declarative memory consolidation during sleep using odor cues. But how is it working?
I have that one recurrent nightmare of my fifth grade German teacher: I’m standing in front of the class trying to perform Theodor Fontane’s “Herr von Ribbeck auf Ribbeck im Havelland” and I fail completely. At this point my teacher starts complaining “See what’s happening if you sleep during class? You forget everything! Now sit down and pay attention!”. If you are still not horrified enough: the next lesson is always maths.
Contrary to my teacher’s opinion it’s widely accepted that sleep is necessary not only for physical recreation but also for memory consolidation. Especially episodes of slow-wave sleep contribute to the hippocampal-neocortical network of explicit memory. Scientists found out that applying low-frequency transcranial direct current stimulation during slow-wave sleep boosts the time spent in slow-wave sleep and enhances memory consolidation. You see where my argument is going? It’s obvious that I forgot Fontane’s poem due to a lack of sleep and not due to my inattentiveness!
If applying electrodes during sleep sounds unhandy to you, why not smelling the scent of roses instead? A recent study explored the possibility to enhance declarative memory consolidation during slow-wave sleep using odour cues. The researchers presented the scent of roses during a visuospatial learning task just before the participants went to bed. During early slow-wave sleep the same odour was presented again to see what effect it has on information retrieval. Compared to a group that didn’t smell the scent during slow-wave sleep the participants performed significantly better on memory retrieval the next morning. The scientists argue that re-presentation of the scent helps bringing up the new information during sleep and thereby facilitates consolidation. Note that the effect was absent in a second experiment where the odour cue was re-presented during REM sleep. Also re-presentation of the cue in awake state had no effect, underlining the importance of slow-wave sleep. If you can’t stand the scent of roses or you’re suffering from allergic reactions don’t bury your head in the sand, it works with simple clicks as well.
In sum, natural odors seem to be a promising and riskless way to enhance your memory consolidation. However, risks and side effects of inhaling your teachers perfume to enhance your memory are to be discussed with your psychoanalyst.
Marshall, L., Helgadóttir, H., Mölle, M. & Born, J. (2006). Boosting slow oscillations during sleep potentiates memory. Nature, 444, 610-613.
Ngo, H. V., Martinetz, T., Born, J. & Mölle, M. (2013). Auditory Closed-Loop Stimulation of the Sleep Slow Oscillation Enhances Memory. Neuron, 78, 545-553.
Rasch, B., Büchel, C., Gais, S. & Born, J. (2007). Odor Cues During Slow-Wave Sleep Prompt Declarative Memory Consolidation. Science, 315, 1426-1429.