Scientists perplexed to find each nostril works separately to sense world

Relatively little is known about how information from the two nostrils is integrated, scientists say

Vishwam Sankaran
Monday 13 November 2023 10:27 GMT

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Each of the human nostrils works independently, smelling the surroundings separately, according to a new study that sheds more light on how the brain processes sensory inputs.

The research, published last week in the journal Current Biology, found that the left and the right nostril smell the world independently, with the sensory signals processed a small fraction of time apart in the brain to get the complete picture of the surroundings.

“Despite extensive work on odor responses in the olfactory system, relatively little is known about how information from the two nostrils is integrated and differentiated in the human olfactory system,” researchers, including those from the University of Pennsylvania, write.

In the study, scientists assessed 10 epilepsy patients who had electrodes implanted in their brains.

Researchers then puffed one of three different scents as well as pure as control into each of their nostrils, and then into both together.

The participants were then asked to detect the smell in each of the trials and also mention which nostril they used to identify.

During this process, researchers used electrodes to collect data on brain’s activity.

Scientists particularly focused on the activity of the brain’s piriform cortex (PC), known to be the site where the sense of smell is handled and interpreted.

Researchers found that when the same smell was puffed into each nostril, the brain activity was similar, but not identical.

Smelling through both the nostrils together also created two separate bursts of activity in the brain separated by a few milliseconds, indicating there was always some level of independence in how the nostrils worked.

“Odor information arising from the two nostrils is temporally segregated in the human piriform cortex,” researchers write.

The latest study, according to scientists, has important implications to better understand how the brain works to process odour.

It proves that the brain maintains distinct representations of odour information arising from each nostril by temporally segregating the signals.

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