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Neuroscientists explain how odors turn into long-term memories

Here’s why certain smells may bring back childhood memories.

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Some odors have the ability to trigger memories, often paving the way for nostalgia — if sentimentally momentous. The methodology of how odors become memories remained a bit foggy; that is, until now.

German neuroscientists from the Ruhr-Universität Bochum examined the conversion of certain odors into long-term memories. The study, led by Dr. Christina Strauch and Dr. Denise Manahan-Vaughan, was published in the journal Cerebral Cortex.

In the study, researchers focused on an area of the brain in the olfactory system responsible for encoding and storing information for retrieval: the piriform cortex.

The piriform cortex, consisting of the cortical amygdala, uncus, and anterior parahippocampal gyrus, plays a major role in human olfaction, like odor perception, among other cognitive activities.

“It is known that the piriform cortex is able to temporarily store olfactory memories. We wanted to know if that applies to long-term memories as well,” said Strauch.

When storing memories, communication between neurons are altered during a process known as synaptic plasticity, thus creating a memory.

Researchers investigated the piriform cortex and whether rats had the ability to express synaptic plasticity. If capable, they also examined if the change lasted more than four hours, which may be evidence of a long-term memory.

To mimic the process of encoding an olfactory sensation as a memory, they utilized different frequencies and intensities of electrical impulses. This process acts on another part of the brain synonymous with memory: the hippocampus.

However, researchers found it did not induce long-term information storage in the form of synaptic plasticity. So they went to a higher brain area to see if the piriform cortex needs to be instructed to initiate a long-term memory.

The orbitofrontal cortex, a higher brain area associated with sensory experiences, was stimulated with a promising change in the piriform cortex.

The study showed that the piriform cortex is associated with the process of storing these memories; however, it only works in interaction with other areas of the brain.

“Our study shows that the piriform cortex is indeed able to serve as an archive for long-term memories. But it needs instruction from the orbitofrontal cortex — a higher brain area — indicating that an event is to be stored as a long-term memory,” Strauch concluded.

The German Research Foundation, a research funding organization, contributed to the study.

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