Have You Ever Wondered Why Some Scents Can Make You Travel Back in Time?

“Smell is very deeply ingrained in our emotional memory,” said Eric Vermetten, a clinical psychiatrist and trauma researcher at Leiden University Medical Center in the Netherlands.

For many experts like Vermetten, the brain’s architecture is an indicator of the close connection of odors to memories.

Unlike the sense of hearing, wherein sound travels from the ears to the brainstem onwards to the thalamus, and then to the auditory cortex, the sense of smell has a more direct connection to the brain. Neurons that sense smells are directly linked to the brain’s olfactory bulb, from where they can be transmitted to the other parts of the brain, which include those related to memory, like the hippocampus, amygdala, and cerebral cortex.

Also, memories built on smells are more accurate, because we have more than 400 types of olfactory receptors, which can provide us with an enormous volume of olfactory details that the nervous system systematically categorizes.

Moreover, based on a mouse experiment by Sandeep Robert Datta, a neuroscientist at Harvard Medical School in Boston, Massachusetts, and his colleagues, they discovered that they could map two extremely different scents in a similar region of the brain cortex. This could be the explanation for why various odors may make up our unique smell remembrances.

“What is crazy is as your experience changes, the actual relationships that are encoded in your brain move around,” said Datta.

However, odors can also bring back sad and fearful memories. Vermetten found this out while treating a Vietnam War veteran who was constantly bothered by the smells coming from an Asian restaurant where he lived nearby.

“He couldn’t sleep at night,” related Vermetten. “It bothered him, and he couldn’t put it aside.”

This prompted Vermetten to conduct a study involving 16 Vietnam War combat veterans, half of whom had Post Traumatic Stress Disorder (PTSD), while half did not. His team exposed the veterans to three kinds of odors: the scent of diesel (closely linked with traumatic experiences during the war); the scent of vanilla; and the unpleasant odor of hydrogen sulfide (which has no connection to the war). It was the scent of the diesel that caused a rise in the blood flow at the amygdala in the veterans with PTSD, but it had less effect on the others.

Hence, Vermetten advises other medical specialists to determine which scents may help their patients or bring back painful memories.

Overall, it is the hope of these olfactory researchers to find ways for smells to help in further improving and healing our brains.