Last week we visited Musée de la Parfumerie Fragonard, a museum created by the Fragonard Perfumery to expose visitors to their perfumes as well as the perfume-making process. As soon as we stepped into the museum we were met with a light flowery scent that filled the entire room. Being led through the museum by our bubbly and efficient tour guide, we learned about how scents are extracted from the oils of flowers, the ways in which these scents are diluted and packaged, and of course where on the body to wear perfume (your wrists and neck if anyone is wondering). At the end of our tour we were able to test a number of fragrances that were available for purchase. I remember instantly loving some of these scents (Etoile in particular, which means star in French) and also having quite a negative reaction to others.
I wondered what parts of my brain process odors as pleasant or unpleasant and if sensory stimuli other than scents can affect the perception of an odor. In a study done by Katata et al. (2009), adult human subjects, 27 females and 3 males, ranging from 18-35 years old were exposed to one of two different chemicals odors while their brains were being studied using an fMRI scanner. An fMRI scanner detects active areas of the brain through identifying an increase in blood flow. The subjects were told to pay close attention to the scent and after the scan they were told to rate the odor based on pleasantness. About half of the subjects were exposed to each odor and the odor was rated on a scale of -3 (strongly unpleasant) to +3 (strongly pleasant). The group found that those subjects which rated the odor as unpleasant had increased brain activation in their lateral orbitofrontal cortex (lateral OFC) and those who rated the odor as pleasant had increased brain activation in their anterior cingulate gyrus. The lateral OFC has been previously shown as one of the brain areas responsible for processing negative aspects of odor and facial appearance; this study provides further support for this claim. The cingulate gyrus has been shown to be involved in olfactory processing when attention to features of odors is needed; this study implies that perhaps the anterior, the front most part, of the cingulate gyrus is involved in specifically processing pleasant stimuli (possibly because we need to pay attention to the features of the odor in order to determine that it is pleasant). This study suggests that perhaps when I smelled a perfume that I considered pleasant, my anterior cingulate gyrus was activated, and when I smelled a perfume that I considered rather unpleasant (which was probably followed by a not-so discreet grimace) perhaps my lateral orbitofrontal cortex was activated. The findings of this study suggest that the activation of these brain areas are involved in olfactory perception, however the subjects were predominantly female and only 30 subjects were used, so these finding may not be universally applicable (although the study does provide further insight into the regions of the brain that may play a role in processing the pleasantness of odors).
As I stated before, upon leaving the museum, I also wondered if any other sensory input could affect an individual’s perception of smell (which could possibly be used as a tactic to sell perfumes). In a study done by Seo and Hummel (2010), the affects of auditory stimuli on olfactory perception were tested. Twenty-six human subjects (20 female and 6 male) between the ages of 20 and 40 were exposed to 1 of 4 auditory cues for five seconds and four seconds after the onset were presented with an odor. The auditory cues consisted of two pleasant sounds, baby laughing and jazz drum, and two unpleasant stimuli, a baby crying and a baby screaming. After auditory cue and odor exposure, the subject was told to rate the odor on a scale of 0 (extremely unpleasant) to 10 (extremely pleasant). The group found that subjects rated the odor as being more pleasant while listening to the “pleasant” auditory stimuli and less pleasant while listening to the “unpleasant” stimuli. This perhaps suggests that auditory cues can influence the way in which individuals perceive an odor. Like the first study, this study uses mostly female subjects which presents complications associated with the auditory cues used. The group chose auditory stimuli related to infant cries and laughing. These stimuli could have evoked a maternal behavior in women, putting the subjects in either a rewarding or fear-inducing state (which could lead them to rate odors as pleasant or unpleasant). Thus, these auditory cues may not be applicable to all individuals as “pleasant” and “unpleasant.” This study, however, does suggest that auditory cues in general may play a role in influencing whether individuals consider an odor pleasant or unpleasant. It would be interesting to see if by playing pleasant auditory stimuli, there is more activation in the anterior cingulate gyrus upon smelling an odor. Conversely, it would also be interesting to explore if by playing an unpleasant auditory cue, there is more activation on the lateral OFC upon smelling the same odor. It may be possible to alter the way that an individual perceives an odor by simultaneously presenting that individual with an auditory cue. Maybe perfume stores should start playing jazz drum recordings in the background while their customers shop. I wish I had remembered if the Musée de la Parfumerie Fragonard played music while having us test their scents. Judging by the amount of perfume one of my friends bought (shout out to Emily), perhaps they were one step ahead of all of us.
– Ankita Gumaste
Katata K, Sakai N, Doi K, Kawamitsu H, Fuji M, Sugimura K, Nibu K (2009) Functional MRI of regional brain responses to ‘pleasant’ and ‘unpleasant’ odors. Acta oto-laryngologica 129: 85-90.
Seo HS and Hummel T (2011) Auditory-olfactory integration: congruent or pleasant sounds amplify odor pleasantness. Chem. Senses 36: 301-309.