You hold a sun cream tube under your nose – and feel the sun, sand and salt on your skin? Or you squeeze into the subway in the morning – and the passenger's perfume beams you back into the arms of your ex?
Odors evoke the strongest, most direct memories. And the most emotional: If we get a smell in the nose, which we know from earlier, the feeling drives us into the limbs, which we connected with him at that time – no matter if it was a feeling of security, fear or a heartbeat in love.
Conversely, if you can not smell good, you may also remember badly. There is a close connection between an impaired sense of smell and dementia such as Alzheimer's. This is now documented by various studies, so that it is being researched whether the olfactory faculty may be used as an early warning sign for such neurodegenerative diseases.
Fragrance stimuli land directly in the emotional core of the brain
A strong link between failing nasal force and dementia has recently been noted again by researchers from Michigan State University. For more than a decade, they reconciled olfaction, disease and death rates in 2289 people aged 71 to 82 years. An important finding: the participants who started the investigation with a bad sense of smell after ten years had a 46 percent higher risk of death than those with a good sense of smell.
But why are nose and memory linked? "Our sense of smell is the only one directly related to our brain's emotional center," says Rachel Herz, who researches the psychology of smelling at Brown University in Providence, Rhode Island, and recently published The Scent of Desire "has published. She was able to show that fragrance stimuli reach the so-called amygdala, the "emotional kernel" of the brain, via a direct path unfiltered. And to the neighboring hippocampus, where our brain processes experiences and forms memories.
Both structures belong to the so-called limbic system, which plays an important role in the processing of emotions. The fact that we associate the scent of apple pie with comfort-filled childhood days, or the perfume with the ex, has a lot to do with these nerve cell bundles.
Herz demonstrated how strong this system can be when recalling it with magnetic resonance tomography: tried-and-tested subjects on their favorite perfume showed significantly higher activity in the hippocampus and the amygdala than in other fragrances.
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Nose, feelings and memories are so closely intertwined. In terms of evolutionary history, this direct connection makes perfect sense: we recognize foul food very quickly – before we put it in our mouths. On the other hand, we experience picture or sound memories as less emotional and therefore less strong. There is a reason for this: Our other senses are not directly connected to the limbic system. They are interconnected and tested via various intermediate stations, such as in a structure called Thalamus, which acts like a filter.
As it happens that we always store fragrances in connection with a particular experience, researchers have now around Afif Aqrabawi from the University of Toronto found out. They used mice to investigate what happens when a certain odor pathway in the brain is disrupted, connecting the limbic system to the nerve nucleus AON (anterior olfactory nucleus). The function of the AON exactly, numerous scientists are trying to explore.
The animals kept sniffing the same source of smell as if they were always rediscovering it. Although the mice were able to perceive the new smell, they could no longer store it and place it in a context. Aqrabawi's Conclusion: The connection between the two brain-capped regions of the brain is crucial to creating complete memories, including the fragrance.
When odors trigger panic
But fragrances are not always associated with pleasant impressions. "Odors are the worst triggers of post-traumatic stress disorder," says Herz. She cites the case of a female soldier who could no longer stand the smell of grilled meat: for her, it was inseparable from deadly attacks in Afghanistan. "That's hard to handle, because the emotional connection is so strong in smells," says Herz.
And even in Alzheimer's patients, smells can still bring back vivid memories – but only at the beginning of the disease. After all, the so-called olfactory bulb, which absorbs odor stimuli from the sensory cells of the nose and forwards them, quickly shrinks. Also, the sense of smell decreases rapidly, until the patients usually no longer perceive odors.
And what does a fragrance-free world do to us? "People without a sense of smell lose their most emotional memories," says Herz. The fun of eating and many other sensual pleasures fall away. Studies show that people who, for example after an accident, could no longer perceive fragrances, were more depressed after one year than those who were blinded by a stroke of fate.
The question remains: Is there a therapy for people who can not smell? A kind of hearing aid for the nose? So far no. But according to odor researcher heart is currently working on it.