The latest findings in Neuropsychology and Neuroperfumery

How sensory experience, synaesthesia and the super additivity of stimuli are linked to certain brain regions and how they can be used for the psychology of fragrance selection.

Joachim Mensing

The latest findings in Neuropsychology and Neuroperfumery

Our ability to sense smell has traditionally been seen as a supporting function to our other senses. But that is also what makes our sense of smell particularly fascinating. It is often experienced with other senses, such as sight and hearing, which makes our experience of scent much more intense.

Synaesthetes — people who can blend their senses — can equate scent to other sensory information, for example, colour and shape. Contrary to popular belief, this ability is not unique to synaesthetes. In fact, to some extent, it applies to almost everyone. One doesn't have to be Kandinsky to see fresh, bubbly citrus notes such as orange, lime green or refreshing turquoise blue; or picture yellow flying triangles when they hear the rhythmic sound of a saxophone. In other words, smell is wonderfully suited to be fused with other senses and experienced as multisensory stimuli, and thereby experiencing an increase — even if there are individual and cultural differences, due to which the merging of individual senses can be experienced differently.

Findings from brain research on synaesthetic and multisensory experience

What is going on in the brain, and where does the impression arise when the senses are fused in a multisensory manner? Neuropsychology and the still-young scientific discipline of neuroperfumery provide fascinating insights into this.

For several years now, neuropsychology and neuroperfumery have improved our observations of the olfactory process with the ever-evolving imaging methods (FMRT — functional magnetic resonance imaging). This research has brought something spectacular to light: individual brain regions, also associated with the localisation of personality traits, seem to have specific scent preferences and favourite scents. These are initially fed to the respective brain regions and their networks as scent stimuli as if someone in the olfactory brain knew which region currently or generally needs stimulation for corresponding scents.

During investigations into the odour preferences of individual brain regions, a brain region was discovered that, with its network, plays a crucial role in conscious odour perception and synaesthetic experience. The orbitofrontal cortex (OFC) is responsible for conscious odour recognition and thus categorising all odours fed to it. It, therefore, coordinates all olfactory impressions and brings them into an overall context, without which perfume enjoyment would not be possible. Consequently, it is not wrong to call the OFC our 'Maître des Perfumes' in the brain.

At the same time, the OFC is the 'Maître of the Senses', which coordinates and is therefore responsible for synaesthetic and multisensory experiences. This is why we can associate colours or music with olfactory sensations. Or, as a small or large synaesthete, you can also see fragrances in colours and shapes. The OFC goes one step further to establish valuable relationships, such as whether a perfume is worth its price or whether the packaging colour suits a fragrance.

Then another discovery was made that would have pleased the visionary extrovert painter Kandinsky. The orbitofrontal cortex and its network — the centre of synaesthetic experience — is also the seat of personality traits, particularly extraversion (feeling more active, dynamic, free and confident) with specific scent preferences. One might have expected a certain fragrance neutrality from the OFC as 'Maître de Parfum'. Still, this brain region with its network especially loves the vibrant freshness of slightly spicy-invigorating aromatic citrus notes and likes to combine them synaesthetically with the colours, shapes, sounds and rhythms.

Favourite olfactory notes and fragrances of extraversion-seeking brain regions — The Orbitofrontal Cortex

Orbitofrontal Cortex
Extraversion Network
Freedom, activity & self-assertion

Associated Colour Groups

Fragrance Examples
Escentric 03 & Escentric 05

Escentric 03 is an example of a fragrance which particularly appeals to the orbitofrontal cortex, satiating its desire and need for stimulation. The OFC is particularly addressed by the top note of Escentric 03 with refreshing notes of ginger root, green peppercorn and Mexican lime.

Similarly, the top note of Escentric 05 has a lot of what the OFC loves. Here it is the citrus notes of bergamot and orange, supported by laurel, rosemary and juniper, that radiate an invigorating, slightly spicy freshness.

Escentric 03 and Escentric 05 are quite complex in the heart note and also address other brain regions, especially in the drydown. Still, from a neuroperfumery perspective, the refreshing, vibrant top notes are a feast for extroverts, not only olfactorily but visually with the turquoise-blue and yellow-green colours of the packaging.

Escentric 03 and Escentric 05 activate another brain region — the piriform cortex — which supports the extraverted OFC through the superadditivity of stimuli in a multisensory manner.

The fragrance manager in the brain or 'the little man in the nose'

The orbitofrontal cortex has an ally in the olfactory brain — the piriform cortex, a small brain region that acts as a fragrance manager in conjunction with other areas and decides on the effect of perfume and smell. This brain region near the olfactory bulb is closely linked to sight and has extraordinary abilities. It can enhance the effect of perfume and fragrance on our consciousness, mood and emotions but also dictates the upstream to the olfactory bulb, which is closely connected to the nose, what and how something is to be smelled. This can go as far as not smelling a particular substance at all or only partially sniffing it, depending on what the piriform cortex and its system perceive to be important.

The piriform cortex also decides what, how and where something is sent to other brain regions for further processing of smells. The piriform cortex has a very emotional, often fear-smelling ally: the amygdala. As a rule, it always smells along and exchanges information about the olfactory impression with the piriform cortex. The result can also be reported to the olfactory bulb in a loopback. An interesting fragrance manager thus guides the effect of perfume and smell on consciousness, mood and emotion. With the piriform cortex, we have a kind of little man in the brain who gently whispers how to deal with an olfactory stimulus. To take our example from above, he first addresses the olfactory stimulus to the orbitofrontal cortex as if he knew that the extraverted OFC is particularly fond of this kind of scent.

As a fragrance manager, the piriform cortex also influences our personality, motivating it with olfactory impulses. Even more so, since the piriform cortex is connected to the sense of sight, among other things, it becomes understandable how the sight of a lemon can enhance the olfactory impression. It is the beginning of a superadditivity of stimuli, whereby ideally, all five senses (visual [optics], hearing [acoustics], smell [olfactory], taste [gustatory] and touch [haptics]) are used to optimise the experience, then merged in the OFC. The brain seems to be particularly fond of the superadditivity of stimuli. As brain research confirms, the joint processing of visual and olfactory stimuli leads to increased brain activity.

Investigations into the influence of individual sensory impressions on smelling bring another exciting result. Although more than 80% of all sensory impressions are consciously received through the eyes, a little more than 10% are acoustically, and only under 4% are consciously received through smell. Nevertheless, the sense of smell plays a crucial role in determining our moods and emotions. This is because we are not consciously aware of most smells. They are processed unfiltered in our emotional centre by the amygdala and its network, which makes a preliminary decision about whether something or someone is perceived as sympathetic or unsympathetic.

Back to the orbitofrontal cortex and its network. Current studies come to further surprising findings. The OFC is mainly connected to three control circuits that enrich olfactory signals and trigger a range of neurobiological and psychological-emotional processes.

Favourite olfactory notes and fragrances of trust and security-seeking brain regions —The Amygdala Loop

Fight or Flight Response Network
Trust, protection & security

Associated Colour Groups

Fragrance Examples
Escentric 01 & Escentric 02

Control circuit one, the so-called amygdala loop, is particularly fascinating for psychologists — on the one hand, because the perception of smell begins here unconsciously and can remain unconscious. On the other hand, smells can modulate emotions through them. Imaging techniques that allow us to observe the brain react to scent have helped us confirm that warm skin, warm wood, musky notes, and milky smells are favourite aromas of the amygdala. The amygdala can react to these notes with deep emotional relaxation, and its otherwise rather jumpy network begins to trust.

It has long been known that the amygdala, which lies deep in our emotional centre (the limbic system) and is responsible for processing smells, is particularly involved in negative emotions such as anxiety and fear. The amygdala control circuit is part of the 'Fight or Flight Response Network', but it also controls positive, pleasant and relaxed experiences and thus the feeling of trust, protection and security.

Perhaps this explains the many positive comments that the Escentric 01 fragrance, with its high Iso E Super content, has received over the years. The woody-cosy-ambery-musky note in this fragrance, launched in 2006, seems to particularly appeal to the amygdala. Another trust and security-promoting fragrance is Escentric 02. It works for the amygdala with its warm amber-balsamic, slightly sweet fragrance character by triggering feelings of emotional well-being and protection. From a synaesthetic point of view as well as from the perspective of the superadditivity of stimuli, both fragrances optically enhance the fragrance experience thanks to their packaging design — Escentric 01 in particular. In colour psychology, shades of purple and violet are associated with inwardness and emotional depth and thus with the amygdala.

Favourite olfactory notes and fragrances of anti-stress-seeking brain regions – The Hippocampus Network

Stress & Memory Networks
Balance, relaxation & harmony

Associated Colour Groups

Fragrance Example
Escentric 04

In control circuit two, the so-called Papez circuit, the focus is on the hippocampus, a brain region in the shape of a seahorse. It is particularly responsible for memory storage and thus for our long-term memory and learning. With the hippocampus, we have an excellent olfactory memory. For example, we remember scents from early childhood and associate them with events and feelings.

Enemy #1 of the hippocampus is stress. Chronic stress can cause this brain area to shrink due to excessive cortisol release, and accordingly, one increasingly loses the ability to name the scents of individual flowers correctly. Clinical studies show that this brain region can shrink by up to 26% of its original size. Therefore, it is understandable that the hippocampus has scent preferences that offer relaxation and anti-stress prophylaxis. Aromatherapy has long known a whole range of promising fragrances against stress. They come mainly from the flower and blossom area, such as roses and softwood notes like sandalwood.

Escentric 04 has a heart note made for the hippocampus. It's a wonderfully calming and loving 'soft rose' accord created from four different rose ingredients. The fragrance certainly appeals to other areas of the brain, especially with its freshness in the top note. But the balsamic drydown with a sandalwood accord really relaxes the hippocampus. When stressed, the brain appreciates soothing pastel tones, and warm, earthy reddish-brown tones radiate harmony, calm, and balance. Furthermore, colour groups associated with self-experience and protection, such as soft purple tones, which are also linked to the amygdala, gain psychological significance.

Favourite olfactory notes and fragrances of pleasure, joy and fun-seeking brain regions – The Hypothalamus Network

Reward Networks
Pleasure, joy & fun

Associated Colour Groups

Fragrance Example
Escentric 05

Control circuit three focuses on the reward system, the so-called dopaminergic system and thus the scent preferences of the hypothalamus and its network. The hypothalamus plays an essential role in the enjoyment of scents. Its network not only controls hunger, thirst and sex drive but also has reward, pleasure and addiction centres that can trigger the feelings of pleasure, joy and fun.

The hypothalamus network is the hub of the highly interconnected dopaminergic system. Dopamine — popularly known as the 'happiness hormone' — is a messenger substance that transmits an excitation from one nerve cell to other cells. It plays a central role in the increase in drive and motivation in the sense of 'wanting something', also in wanting a certain smell for enjoyment.

The hypothalamus and its network have their own scent preferences. The favourite scents of this system are chocolate, followed by vanilla and cinnamon scents, but also fruit scents. Above all, it must smell sweet and seductive, like fully ripe figs. However, the system is not particularly picky regarding cravings or cravings for sweets. The main thing is that it smells edible. In perfumery, the scent direction of the gourmand notes smells like delicious desserts and fits precisely into the requirement profile of the dopaminergic system.

In Escentric 05, the hypothalamus smells a delicious fig right from the top note. In addition, the fresh fruity aroma of bergamot and orange arouses the interest of the citrus note lover orbitofrontal cortex and its network. Finally, the warm base of Cashmeran and pine resin, reminiscent of wonderful summer days in the Mediterranean, adds to the all in all happy scent for the reward and pleasure network.

Escentric 05 is certainly not a pure gourmand fragrance. As typical gourmand notes radiate, 'sweet, edible seduction', they are often associated with red and magenta in colour psychology. Still, if magenta reds are drawn to you at the moment, your olfactory brain wants to smell the fig out of Escentric 05 in search of more happiness. In summary, the psychology of fragrance selection is more closely tied to cravings for sweets than we think, especially when dieting, even if we believe sweet scents don't appeal to us at all.

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Further reading: Joachim Mensing - Schöner Riechen — The magical effect of perfume on well-being, Springer Heidelberg 2021