This is probably one of the most important areas of aromatherapy and relates to the effect aromas have on the mind and particularly the emotions. It is essential to wellbeing and is brought about by olfaction, through sniffing or vaporising essential oils and helps to explain why some oils are relaxing, whilst others are stimulating or calming.

Different scents produce specific emotional Males, communicated through the various neurotransmitters. Volatile essential oil molecules are inhaled and reach the olfactory mucous membrane with its sensory receptors. Here the sensation of smell passes up the olfactory bulb, which is in amplifier through the olfactory nerve and passes to the limbic centre within the brain.

When discussing likes and dislikes of aromas, these will vary from individual to individual because one's perceptions are based on many factors, some conditioned memories and others through experiences, either pleasant or unpleasant. For example, many people dislike the smell of hospitals because it evokes a strong memory/emotion of perhaps a traumatic experience. However this effect could be put to therapeutic use if we use an aroma to condition the patient/client to a pleasant experience. Then just by sniffing that aroma, we could evoke positive responses, such as relaxation or being uplifted. This hypothesis is echoed by Michael Kirk-Smith where he says that "Olfaction is unique amongst the senses in its direct connections to the neuroendocrine and limbic structures of the brain. This suggests that the olfactory system and olfactory stimuli may have potential uses in the treatment of various disorders, both physiological and psychological". This could (therefore be useful for people who suffer panic attacks or depression for example. According to research by biochemist George Dodd PhD, and psychologist Steve van Toller PhD., at the Warwick Olfaction Research Group, the effect of fragrance on the brain is similar to that of some antidepressant drugs. Another piece of interesting research in this line of thinking shows how insulin was injected into healthy male volunteers once a day for four days and their blood glucose was measured (it fell). At the same time, they were exposed to a smell. On the fifth day they were just given the smell, and, their blood glucose still fell (Stock horst & Gritzmann, (1999) Psychosomatic Medicine 61, 434-435).

We certainly appear to have an innate ability to detect bad, aversive smells and this probably is a type of early warning system. We call the limbic system the "emotional" brain because this is where our thought processes and memories are stored. You could say that this part of our brain is like a lock and key mechanism when discussing aromas.

The lock is the actual smell memory; the key-is the scent which opens the mind to the memory. In aromatherapy, the brain responds to the aroma of an essential oil by retrieving a past memory associated with the aroma, good or bad. This is in important reason for not burning essential oils in an open environment, as it could trigger an unpleasant memory for someone in the room. Where the aroma is unknown to you, the brain creates a new memory response. As you may have noticed, sometimes it can lake a while to get used to and like a new aroma or to change your perceptions of an aroma/essential oil over a period of time. As a result, the memory responses from the essential oils can be relaxing, balancing, energising, uplifting, etc.

The sense of smell has the longest retail of all the senses, so we hold memories associated with aromas for quite some time. It is amazing how a certain smell can evoke a memory from childhood and you can visualise it clearly in your mind's eye.

When looking at the parts of the limbic system, one of the main parts chat interest aroma therapists seems to be the prefrontal cortex, which is in essence the "chief executive part" of the brain. This structure has been implicated in all kinds of behaviour, from planning activities to reactions to situations and thus has been concluded to be, along with the basal ganglia, the key area involved in the behavioural aspect of emotional reactions. Also, the orbitofrontal cortex plays a similar role, relating to controlling alterations in our mood or mental state.

As we do not have enough space here to fully explore all the limbic system, I will next focus on the hippocampal formation, which is very complex. It consists of three main parts playing a crucial role in the formation of specific types of memories. These are involved in directing memories received from the special senses and this explains their ability to bring together visual memories with smells and sounds and in a sense fix memories in space and time and therefore is responsible for saving and retrieving long-term memories.

According to

http://www.austen.350.com/silver_lockers/ORa-Environmental-A.html, certain aromas have also been shown to increase alertness, enhance productivity in repetitive tasks and have positive impact on creative efforts. It also reports that the Japanese began testing the effect of natural aromatic plant extracts by measuring the brain waves of subjects after they smelted a particular fragrance; they found that some scents produced a brain-wave pattern that indicated calm while other scents produced a pattern indicating mental stimulation. Further studies have been undertaken by Tim Jacob (2000), but these controlled trials found that there was "basically no statistically significant difference between the control state and the odour state" when looking at the alpha wave activity within the brain of rosemary and ylang ylang essential oils. He postulates that maybe it is a lot to do with conditioning and psychological influences as discussed above.

Aromatherapy is criticised for not having enough research- based evidence to prove its efficacy as most of the published usage is anecdotal in nature. However I agree with Robins J who points out that "patient satisfaction and wellbeing are outcomes that need to be considered because they may justify our ethical use of aromatherapy even if well controlled trials... do not provide positive results".

© Carole Preen
Aromatherapy Consortium
P O Box 6522, Desborough,
Kettering, NN14 2YX
Tel: 0870 774 3477
www.aromatherapyregulation.org.uk

Reproduced with the kind permission of Today's Therapist