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Scent, semantics and cinnamon scrolls

28 Sep 2012
Kjelvik G., Evensmoen H., Brezova V. et al (2012). The human brain representation of odor identification. Journal of Neurophysiology 108:645-657 Details

Customer study highlights:

For some, the aroma of cinnamon scrolls brings with it memories of tea time at grandma’s house: of hot tea in teapots, of ironed tablecloths and the best china. For Proust and his remembrance of things past, it was the Madeleine.

Sometimes we can only allude to the events the smell is associated with ("it smells of Christmas"). Often, when we pull at the words to describe a smell, we pull lost memories along with them. This "odor identification" (OI) is a complex task; we recruit many different areas of the brain to help us disentangle the name of a smell from countless others. One of the circuits involved is intimately linked to learning and memory.

In their study, Kjelvik et al tested 17 women who were each asked to lie on a scanning table within an fMRI machine while odors were released into the air within the scanning chamber. A piezoelectric respiratory belt connected to a PowerLab allowed the researchers to monitor breathing depth and rate in order to control for any effects these may have on odor perception and brain activity.

As expected, "passive smelling" activated olfactory (smell) areas. When subjects correctly identified odors, activation was instead seen in the hippocampus and entorhinal cortex (areas used for semantic and episodic memory).

It turns out that understanding the connection between brain circuits involved in smell and memory is important. OI deficits in Alzheimer's disease correlate with the number of tangles seen in the entorhinal cortex and hippocampus. This means that OI testing may be useful in neurological assessments. If we know when the smells are beginning to pull away, we may have a hope of preventing the memories being pulled along with them. That way, our memories – of grandma’s china and hot tea – need only be sniff away.

By Matthew Goddard

Science Manager

Researcher, Dad and motorbike racer.