Have you ever been what seemed to be randomly flashed back to a memory, only to realize a moment later that there's a specific smell around you that triggered it? Chances are that you have -- isn't it wild how profound the effect is? Not only are you thrown back to a moment passed, but the details of that instance can be so vivid! How you felt, what you did during that day or even during that time of your life!
The science of smell
This is a seriously interesting field in science, and we're just starting to map out the area. What we know is, in terms of smell, that the odor molecules bind to receptors in our nose, and initiate electrical impulses in nerve cells which transmit different signals to the brain. We humans have around 400 different olfactory (smell) receptors at work, and they can often detect more than one type of odor. So, the communication to the head office can be really complex! Once the signals arrive in the brain, they are relayed at the thalamus, which is like a control center that decides where to send the signals for further processing. It’s at this point where the fun really starts to happen. For example, if you smell something from your childhood, the signal can be sent out to conjure up that memory, in which you likely also have embedded certain emotions. There are some key areas for this in the deeper parts of the brain, called the hippocampus and the amygdala. These regions, very simply put, are involved in the processing and storing of memories, dealing with emotions (particularly fear), as well as learning.
Relationship to aromatherapy
Other effects don’t have to be connected to memories and emotions, but can influence our current state in terms of wakefulness or attention. Different odorants can trigger various effects in the brain – for example, inhaling the scent of rosemary essential oil has been found to cause the release of noradrenaline: a neurotransmitter and a hormone. The general effects of this is to get you ready for action: you get alert, your attention gets sharper, and your blood sugar levels rise as glucose is released from energy stores. Another example is rose oil, which has been found to affect the HPA-axis (our stress-system) in such a way that it reduces the amount of circulating cortisol (stress hormone). These are just two examples of the effects of essential oils – two of the few we have managed to research properly.