Making Memories One Sniff at a Time

Earlier this week we visited Le Grand Musée du Parfum, or for those of you who don’t speak French, the grand perfume museum (kind of easy to guess). Before arriving, I didn’t know what to expect besides that we would smell a whole lot of perfume. I was right, the building was filled with a variety of fragrances waiting to be sniffed, but this was not the only thing the museum contained. We walked through a maze of rooms displaying all sorts of information about perfume, starting with a historical journey of the origins from ancient Egypt to the Roman Empire and all the way to present time. Following the history was a sensory immersion exhibit (my personal favorite being a neuroscientist) that explained how our sense of smell works and contained olfactory games and fragrant riddles. Lastly, the museum had an exhibit dedicated to the art of the perfumer, where they had a collection of raw materials, natural and synthetic, most commonly used by perfumers. By the end of the museum my odor receptors were exhausted.

smelling one of the perfumer’s raw materials

My favorite room of the museum was the jardin des senteurs, or garden of the scents. We were told to walk up to these large white flowers, close ours eyes, breathe in the odor, try to guess what scent we were smelling and see if it triggered any memories. I did exactly this and took a big whiff of the first odor. Immediately I could recognize the smell of a campfire and a memory was triggered. I pictured myself sitting around a fire with my dad and sister and we were roasting marshmallows, an activity I love to do! I opened my eyes and was surprised and fascinated at the same time by this result. I quickly moved on to the next flower, closed my eyes, and sniffed. I was instantly at my grandma’s house on Christmas morning and an aroma floated through the air. It was cinnamon! I was reminded of the freshly baked cinnamon cookies we made around the holidays.

Jardin des Senteurs (garden of the scents)

Engrossed by this activity, I wondered if different areas of the brain were used when forming and retrieving memories of events in the presence and absence of strong odors. I did some googling and found a recent study that investigated the brain areas involved in episodic memory retrieval, or memories of a specific event, depending on the presence of an odor during encoding, the initial learning of new information (Galliot et al., 2013). Participants in the study consisted of thirteen female students between the ages of 20 and 23 (interestingly no males were used because olfactory abilities and brain regions can differ between genders). The experimental task consisted of two stages. In the first stage (encoding), 32 colored pictures of objects or animals were presented on a computer screen and participants were asked to determine if each picture contained more or less than three colors. This ensured the participants examined each picture carefully, but remained unaware the test was related to memory. During this task participants wore a mask with a valve that contained filter paper soaked in either water or vanillin, an olfactory stimulus usually considered pleasant. Half of the participants wore a mask with vanillin odor for the first 16 pictures and the other half wore the water filtered mask. The participants switched masks for the second 16 pictures.

types of memory

Two weeks later, the second stage (recognition) of the experiment was conducted. During this stage, each of the pictures used in the first stage (target) were presented simultaneously with a new picture (distractor). After the presentation of the two pictures, participants were instructed to press either a left or right button according to the side of the computer screen the participant believed was the target picture. For the duration of this task, participants were in an fMRI machine so that the investigators could record their brain activity. They found brain areas known to be strongly associated with episodic memory retrieval, the posterior hippocampal formations and the anterior thalamic nucleus, were activated whether or not an odor was presented in the first stage. However, they did find that learning in the presence of an odor causes activation of additional brain areas during the retrieval task. One of these areas was the orbitofrontal cortex and it has been previously described as the main site of secondary olfactory processing. They also found other areas in the frontal lobe of the brain, the superior, middle, and inferior frontal gyri (the bumps on the brain), were activated more during presentation of images encoded in the presence of the vanillin odor. However, the specific role in olfaction of these three brain areas remains unclear. I was very fascinated by the results that memories made in the presence of odors activated different brain regions during retrieval.

orbitofrontal cortex

The study also found that there was no significant difference between the number of correct responses of the target images between the pictures encoded with the presence of an odor and the pictures encoded without an odor. This finding made me wonder if the researchers had presented the odor during the retrieval stage of the experiment, would it increase the number of correct responses of the target images encoded with the vanillin odor? When I smelled the campfire and cinnamon odors, my memories were triggered instantly, so I would hypothesize if the participants smelled the vanillin during the recognition task, it would enhance their memory and would increase the number of correct target responses for the pictures encoded with the odor.

Now as I walk through the streets of Paris smelling the freshly baked breads and desserts, I will be reminded that the memories I form will cause different areas of my brain to be activated among retrieval.

Sources:

Galliot E, Comte A, Magnin E, Tatu L, Moulin T, Milot J (2013) Effects of an ambient odor on brain activations during episodic retrieval of objects. Brain Imaging and Behavior 7:213219.

Pictures 1 and 2 were taken by Dr. Kristen Frenzel

Picture 3: http://www.mindauthor.com/psychology/semantic-episodic-memory/

Picture 4:  https://commons.wikimedia.org/wiki/File:MRI_of_orbitofrontal_cortex.jpg

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