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Science of the brain: How smells become our memories?

Posted April 25, 2014

Have you ever had an experience when you perceive a smell and suddenly remember an event that you’d forgotten for years? Or consider certain perfume or cologne smells that remind you of people in your life. It is well known that smells can transport us back to powerful and emotional memories from the early life experiences more effectively than sounds, pictures or stories. Why does the smell seem to act as such a powerful memory trigger?

Image credit: Derek Hatfield/Flickr (CC BY 2.0)

Image credit: Derek Hatfield/Flickr (CC BY 2.0)

The phenomenon has been studied by researchers at the Kavli Institute for Systems Neuroscience in California and have found that odours connect to memories through an associative process where neural networks are linked through synchronized brain waves of 20 – 40 Hz.

How did the scientists found a link between two neural pathways – smell and memory?

The scientists used rats as research object. These rodents were placed in a maze where strategically placed smells would inform the animal where food could be found. When poking into the hole, the rat was presented with two kinds of smells: one smell told the rat that food would be found in the left cup behind the rat, another smell of food was placed in the right cup. In the first cup was hidden the scent of bananas, in the second one a whiff of pine tree meant as the jackpot. After three weeks training, 85 percent of the rats were able to determine, based on smell and memory, where to go for a reward.

16 electrodes were inserted in the hippocampus (is a part of the forebrain, located under the cerebral cortex and is responsible for memory) and in different areas of the entorhinal cortex in order to see what happened in brain during the experiment. The researchers suggested that the rats became more familiar with the maze’s purpose and their brain waves began to synchronize. This synchronization was found in a specific connection between an area of the entorhinal cortex, lateral entorthinal cortex, and an area in the hippocampus. The range was between 20 and 40 Hz. What’s  especially interesting is that the same activity was not seen at a comparable strength anywhere else in the brain.

A whiff of the same scent – even years or decades later – reactivates these previously synchronized networks and pulls the associated memory trace from the depth of our mind. That means fragrances have a power to cause our brain to translate the scent into memories by matching up with signals fired when you first sniffed is all those years ago. Our brain is like a map and each recorded smell is placed like a pin in it.

These findings do extend previous research by demonstrating that odour is a stronger trigger of detailed and arousing memories than music, which has often been held to provide equally powerful triggers as odours. Besides, this experiment gives us an interesting look into the inner workings of our brains, so that the next time you smell new perfume or whatever else and it brings you back to the first time friend met, you’ll know what processes brought you to that memory.


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