Lab Talk

perfume and EEG

What does EEG have to do with Perfume?

Why are large perfume companies building EEG divisions? Fragrances evoke memories, thoughts and feelings and the perception of smell is a complicated science.  

Nestled among the high rise buildings of New York, Sao Paulo, Paris, and Singapore (to name a few) you can find the labs and offices of the modern day perfume industry.

This is where individuals, skilled in the art (and science) of perfume, blend together interesting smelling molecules which ultimately become the tiny drops of fragrance oil which not only go into the bottle of perfume or aftershave sitting on your dresser, but also into your laundry detergent, your shower gel, your dishwashing soap, your antiperspirant…(I could go on).

Next time you are taking a bath or shower, take a look at the bottle of soap or shampoo. In the list of ingredients you can usually find the word “fragrance”.

But this word doesn’t do justice to the multi-billion dollar industry that is hidden behind these 9 letters. And what if I told you that these companies have EEG divisions. Yes, EEG.

Perhaps you might ask, why on earth are perfume companies like Takasago, Symrise and Givaudan using EEG?

The perception of fragrance

Smells, like images or music, have the ability to evoke memories and influence your thoughts and feelings. Indeed this has even evolved into an entire field of aromatherapy, designed to heal your stress and enhance your mood (see this review by Rachel Herz).

What’s more, smells typically operate at a subconscious level, without you even noticing – take a look at this study here by researchers at Northwestern University as an example.

However, our perceptual response to smell isn’t as straightforward as it is to visual or auditory stimuli.

You just have to consider the chemical dynamics of what happens when you smell a fragrance mixture of 100+ different ingredients to realize how complicated it is. The different molecules arrive at your nose at different rates. The perceptual experience changes with every breath, every sniff. The fragrance evolves over time so that what you smell when you first apply a fragranced product is different to what you smell a few hours later. Not to mention that you adapt and habituate to fragrances over time, meaning that both your nose and brain can down tune their sensitivity and response to the smell over repeated or sustained exposures.

There is also the added element that your sense of smell is malleable throughout your lifetime. The connectivity pathways between your nose and brain are constantly being updated based on your olfactory experiences. Not only prenatally and during childhood, but also when you are an adult, changing the way you perceive a fragrance (see this review here by Jessica Brann and Stuart Firestein).

Fragrance and EEG

The complexity of olfactory perception adds up to quite a challenge even for the most expert olfactory EEG researcher. But how else can you really start to understand what is happening inside the human brain when you catch a whiff of someone’s perfume (or a disgusting malodor) except by using a technique such as EEG (see What does the EEG measure? for more on this technique).

Advances in wireless EEG systems (see Taking Neurotechnology out of the Lab) have offered the research divisions of these fragrance companies the opportunity to measure real-time brain responses in a cost-effective, rapid and meaningful way to support the process of fragrance development. This can help them to understand the multisensory interactions between smell and the other senses; to measure the amount of attentional engagement; or to study the emotive impact of a fragrance.

Indeed, different fragrances can produces fundamentally different dynamical responses in brain activity.

Plant researchers Sowndharajan and Kim at the Kangwon National University in Korea summarize here some of the various findings from studies of EEG responses to different plant fragrances. The various studies demonstrate the arousing (activating) or relaxing properties of the individual fragrance oils derived from plants, typically by analyzing the main EEG frequency bands like alpha and beta. This information can be used by fragrance companies to help guide their perfume development process.

Understanding Individual and Cultural Preferences

From a research perspective, EEG can help the scientists within these global organizations reveal how olfactory responses vary across different populations and cultures around the world to understand how experience, culture and personality can drive differences in fragrance perception and preference. Highlighting why some people prefer fruity, floral fragrances, whilst others prefer woody, earthy ones. And showing how this diversity is manifested in the intricate world of the human brain.

Of course EEG can’t tell you how to create the perfect fragrance. That is still the job of the master perfumers who train for many years at a handful of perfumery schools located around the globe. Individuals whose expertise is so cherished that their fragrance formulations are kept top secret, only known to a handful of people.

But the next time you are washing your hands with a fragranced soap, or putting away some freshly washed laundry, pause for a moment and consider what your EEG might look like.  And to help along that thought, here is a table of what people have already found (from Sowndhararajan and Kim, 2016)

Table 2. Effect of inhalation of aroma on electroencephalograph (EEG) activity.
S. No.Odorant MaterialsEEG Wave ChangesBrain FunctionsReference
1.GalaxolideAlpha decreased.Odors produce divided attention even when undetected.[74]
2.m-XyleneAlpha increased.Stimulating and excitatory effects.[75]
3.Birch tar, galbanum, heliotropine, jasmine, lavender, lemon and peppermintIncreased theta for birch tar, jasmine, lavender and lemon.Subjects differed in their subjective responses to the odors.[80]
4.5-α-Androstan-3-one, bangalol, white sapphire, indole, linalyl acetate, eucalyptus oil and ammonia.Alpha increased.From more anterior electrodes—related to psychometric responses.[70]
5.Phenylethyl alcohol and valeric acidValeric acid—alpha 2 increased.Unpleasant odor leads to a cortical deactivation.[76]
6.Lavender and rosemaryLavender—beta increased. Rosemary—frontal alpha and beta decreased.Lavender—increased drowsiness. Rosemary—increased alertness.[9]
7.Synthetic odors—almond, chocolate, spearmint, strawberry, vegetable, garlic, onion and cumin Odors of real foods—chocolate, baked beans and rotting porkChocolate odor—less theta activity.Reduced level of attention.[59]
8.Chewing of marketed gumAlpha power increased.Arousal psychosomatic responses.[77]
9.Valeriana off, Lavandula off, Passiflora incarnata, Piper methysticum, Melissa off, Eschscbolzia californica, Hypericum perforatum and Ginkgo bilobaValerian extract—delta and theta activity increased and beta activity decreased.Self-rated tiredness increased under some of the plant extracts.[13]
10.(R)-(−)-, (S)-(+)- and (RS)-(±)-forms of linalools(RS)-(±)-linalool—greater decrease of the beta wave after work than before work.(RS)-(±)-linalool and (R)-(−)-linalool -favorable impression. (S)-(+)-linalool—unfavorable impression.[88]
11.Chewing regular gum or gum base without flavorAlpha-2 and beta-2 increased for regular gum and decreased for gum base.Activates different brain neuronal populations.[83]
12.Sedative effects—lemon, lavender and sandalwood Awakening effects—jasmine, ylang-ylang, rose and peppermintAwakening fragrances—decreased alpha and beta activities.Sedative fragrances—improvement in productivity.
Awakening fragrances—effect in mitigating the workload.
13.Lavender, chamomile, sandalwood and eugenolAlpha 1 decreased at parietal and posterior temporal regions.Subjects felt comfortable.[61]
14.Chewing gum with and without flavor and flavored aromatic oilChewing gum with flavor and inhale aromatic oil increase alpha and beta waves.Induce concentration with a harmonious high arousal state in brain function.[84]
15.Enantiomers of linalools(R)-(−)-linalool—beta decreased after hearing environmental sound. Mental work—beta increased.Odor perception and responses—chiral dependence and also with task dependence.[89]
16.Aroma of soybeans heated to various temperaturesAlpha wave increased—heated after immersion in fructose–glycine solution.Amino-carbonyl reaction aroma products increase brain alpha waves.[78]
17.β-DamascenoneNon-significant trend for left frontal differences in EEG associated with different liking responses.Left frontal response associated with liking an odor.[91]
18.Lavender and rosemary aromasInduce left frontal EEG shifting in adults and infants with greater baselines than right frontal EEG activation.Associated with greater approach behavior and less depressed affect.[97]
19.General workers, perfume salespersons and professional perfume researchersProfessional perfume researchers respond to odors mainly in the frontal region.Functional coupling for people—occupationally exposed to odors may be related to psychological preference.[71]
20.Lavender and rosemaryIncreased relative left frontal EEG asymmetry.Infants of depressed and non-depressed mothers respond differently to odors.[62]
21.Para-cresol 4-methylphenol, 2-heptanone, methional 3-methylthiopropionaldehyde and dimethyltrisulphide.Theta wave activation in frontal region between the different populations.Cultural differences in odor responsiveness.[93]
22.Pleasant odorBeta wave increased in the left frontal region.Enhancement of left frontal brain region by a pleasant odor.[92]
23.Neroli and grapefruit oilsSlow alpha (8–10 Hz) and theta activities increased in the occipital region.Reduce the cortical deactivation or promote a relaxed state.[79]
24.Low-dose alcoholTheta power decreased in both hemispheres in the high-dose condition.Corresponding to working memory demand.[81]
25.Odor of incense and rose oilFast alpha activity increased in bilateral posterior regions during incense exposure.Cortical and function of inhibitory processing of motor response.[14]
26.Citrus bergamia oilNegative percentage changes of the ratio of low to high frequency in the music, aroma and combined groups than control group.Listening to soft music and inhaling Citrus bergamia essential oil—effective method of relaxation.[90]
27.Abies sibirica essential oilIncreased theta activity after the visual display terminal task.Prevention of visual display terminal—mental health disturbance.[15]
28.Lavandula angustifoliaGood sleep quality—occipital and parietal alpha decreased, frontal theta and occipital beta increased. Poor sleep quality—theta increased in the all cranial regions.Beneficial effect for female adults with sleep disorder.[98]
29.Lavender oilTheta and alpha activities increased.Relaxing effect of inhaling lavender oil.[12]
30.Essential oil of Zizyphus jujuba seedsFast alpha increased in the left prefrontal, right prefrontal and left frontal regions.Increasing attention and relaxation.[99]
31.Essential oil of Mentha arvensis L. f. piperascens aerial partsRelative fast alpha increased. Gamma and the spectral edge frequency 90% decreased.Reducing mental stress.[100]
32.Jasmine oilBeta wave increased in the anterior center and left posterior regions.Increased—feeling of well-being, active, fresh and romantic.[102]
33.Ylang–ylang essential oilProlonged the latencies of P300Not affect information processing resources in patients with TLE.[63]
34.Essential odors—mint and lemon Commerical odors—criton-verbena, lize, melody and rozanAll odors affected the EEG waves in at least some subjects.Essential odors stimulated more than commercial odors and women are more sensitive than men.[35]
35.Pan-fired Japanese green tea (Koushun and Kouju)Kouju affect the beta 1 at right frontal region.Improve memory task performance.[103]
36.Magnolia kobus flowerAbsolute alpha decreased at left parietal region.Awaken and increase the concentration states of brain.[101]
37.Strawberry aroma (food) and the odor of lily of the valley (non-food)Specific scalp potential maps for the two conditions.Food odor—associated with the processing of rewards.
Non-food odor—reflects odor characteristics excluding the reward.
38.Hyperbaric oxygen exposureFast delta decreased and alpha increased in the posterior regions.Oxygen-toxicity diving-related problems.[151]
39.Lemon, peppermint, and vanillaTheta showed statistically significant results between different odor conditionsStimuli can affect the frequency characteristics of the electrical activity of the brain.[16]
40.Isomers of limonene and terpinolene(+)-Limonene—relative high beta increased in the right temporal region.
Terpinolene—relative mid beta decreased and relative fast alpha increased in the right prefrontal region.
Terpinolene—reducing the tension and increasing the relaxation and stabilization states of brain function.[17]
41.Essential oil of Inula helenium rootTheta (in all the regions except T3), beta (Fp1) and mid beta (P4) and relative theta (Fp1, Fp2, F3 and F4) decreased.Enhance the alertness state of brain.[60]
42.Lavender and bergamotThe absolute theta increased at the right prefrontal region Significant differences in the relative fast and slow alpha.Both physical and mental states became more stable and relaxed.[64]


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