Why Odours Can Remind You of the Past

S u m m a r y :
Odours are stored as long-term memories in a particular brain region, which could explain why some smells can remind you of the past. The new findings are published in the journal Cerebral Cortex.

Have you ever experienced an odour that takes you down memory lane? One particular smell will trigger memories of some event that happened years ago. The new study might help us better understand this phenomenon. Conducted by neuroscientists the Ruhr-Universität Bochum, the research looks into the brain region involved in the storage of odours as long-term memories, shining the light on the piriform cortex, a brain area in olfactory senses.

The piriform cortex was previously known to stored olfactory memories on a temporary basis. The aim of the new study, as explains co-author Christina Strauch, was to investigate whether long-term memories were also stored there. To achieve this, Strauch and her partner, Denise Manahan-Vaughan, analysed the piriform cortex of rats for an ability called synaptic plasticity. The latter process ‘interferes’ with the communication between neurones, altering it at the junctions separating different neurones (synapses) to allow for the creation of a memory. The neuroscientists wanted to find out whether synaptic plasticity occurred in the piriform cortex of rats, and if this change could last for over 4 hours, which would be an indication of long-term memory.

Strauch and Manahan-Vaughan sen electrical impulses to the brains of the rats to reproduce the same situation governing the storage of an olfactory sensation as a memory. Applying stimulation protocols whereby the frequency and intensity of these pulses were varied, they caused long-term effects in the hippocampus, another brain region playing a role in making long-term memories. Interestingly, these protocols did not lead to the long-term memory storage through synaptic plasticity in the piriform cortex.

So, the team hypothesised that the piriform cortex might be requiring an instruction from another region to form a long-term memory. When they stimulated the brain area responsible for differentiating between sensory experiences, the orbitofrontal cortex, the desired modification in the piriform cortex occurred, showing that the piriform cortex acted as an “archive for long-term memories,” says Strauch; it just needs “instruction from the orbitofrontal cortex—a higher brain area—indicating that an event is to be stored as a long-term memory.


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