Summary: New research reveals that the names we assign to odors can significantly influence how we perceive them. In a study utilizing ultrahigh-field functional MRI technology, participants rated identical odors as more dissimilar when they were given different names, underscoring the impact of language on sensory experience.
The study tracked how odor information is processed in the brain’s primary olfactory cortex, specifically the piriform cortex, and showed different brain activities based on the labels used. This indicates that our sense of smell is not only about the odors themselves but also how they are contextually represented through language.
Key Facts:
- Identical odors were perceived as more dissimilar when labeled differently, highlighting the strong influence of semantic context on odor perception.
- Functional MRI scans revealed that the piriform cortex’s response to odors varies depending on the labels attached, suggesting a blend of sensory and linguistic processing.
- The study links specific areas of the piriform cortex with broader language processing regions in the brain, suggesting an integrated response to named odors.
Source: University of Tokyo
Our brains process odors differently depending on the names assigned to them, according to new research. Participants were asked to sniff similar odors, for example two citrus scents, and then rate how dissimilar they thought the odors were.
Researchers found that identical odors which had been given different names were rated as being more dissimilar than if they were labeled as being the same.
By using ultrahigh-field functional MRI technology, the researchers could see how the information, the odor and labels, was processed in the area of the brain that identifies odor, and how this differed depending on the label used.
This research helps us better understand the context-dependent experience of odors and how language can affect our daily life.
Would a rose by any other name smell as sweet? Or stinky tofu as … stinky? Maybe not. It turns out that the labels we give to things affect the way we perceive their odor and, according to new research, can even make us think that identical odors smell different.
Researchers have discovered that giving names to odors not only affects our perception of them but how they are processed in our primary olfactory cortex, the area of our brains related to our sense of smell.
Participants were given minty and citrusy odors to sniff, which had been labeled with two words; for example, mint-menthol or eucalyptus-menthol. While sniffing, participants were scanned using an ultrahigh-field (7-tesla) functional MRI (fMRI) machine.
While MRIs take snapshots of the brain, fMRIs enable researchers to see activity in the brain over time, in this case where in the brain the information about the labeled odors was being processed. After the scan, participants sniffed the odors again, but this time presented in pairs, and then rated how similar or different they thought the odors were from each other.
In this second round, the odors and their labels were either the same, or two identical odors were given different labels, or different odors were given the same name.
“We were surprised to discover the clear effects of labels on the participants’ ratings of odors. We could also see from the fMRI results how the semantic context, the word labels used, influenced odor-coding activity in the piriform cortex, a key part of the primary olfactory cortex for processing smell,” explained Associate Professor Masako Okamoto from the Graduate School of Agricultural and Life Sciences at the University of Tokyo.
“Although we knew that the perceptual aspects of odors are processed in the primary olfactory cortex, which the piriform cortex is part of, until now it was unclear whether word labels influenced odor representation in this brain region as well.”
Results showed that participants reported a greater difference between odors when two identical odors were given different names, than when they were labeled the same. The fMRI data showed that some parts of the piriform cortex were affected by the words used to label the odors, while other areas were more affected by the odor itself.
The researchers suggest that this may be because areas affected by words would differ from those affected by odors within the primary olfactory cortex, but further research is needed to confirm this.
The team also noticed a significant connection between the areas within the piriform cortex affected by words and other regions of the brain involved in language processing.
This study furthers our understanding of how language and our sense of smell are intertwined, and how flexible our perceptions of odors can be. Something to think about when you choose your next scented “berry bonanza” candle or “fresh cotton mist” detergent.
About this olfaction research news
Author: Nicola Burghall
Source: University of Tokyo
Contact: Nicola Burghall – University of Tokyo
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Semantic context-dependent neural representations of odors in the human piriform cortex revealed by 7T MRI” by Masako Okamoto et al. Human Brain Mapping
Abstract
Semantic context-dependent neural representations of odors in the human piriform cortex revealed by 7T MRI
Olfactory perception depends not only on olfactory inputs but also on semantic context. Although multi-voxel activity patterns of the piriform cortex, a part of the primary olfactory cortex, have been shown to represent odor perception, it remains unclear whether semantic contexts modulate odor representation in this region.
Here, we investigated whether multi-voxel activity patterns in the piriform cortex change when semantic context modulates odor perception and, if so, whether the modulated areas communicate with brain regions involved in semantic and memory processing beyond the piriform cortex.
We also explored regional differences within the piriform cortex, which are influenced by olfactory input and semantic context.
We used 2 × 2 combinations of word labels and odorants that were perceived as congruent and measured piriform activity with a 1-mm isotropic resolution using 7T MRI. We found that identical odorants labeled with different words were perceived differently.
This labeling effect was observed in multi-voxel activity patterns in the piriform cortex, as the searchlight decoding analysis distinguished identical odors with different labels for half of the examined stimulus pairs.
Significant functional connectivity was observed between parts of the piriform cortex that were modulated by labels and regions associated with semantic and memory processing.
While the piriform multi-voxel patterns evoked by different olfactory inputs were also distinguishable, the decoding accuracy was significant for only one stimulus pair, preventing definitive conclusions regarding the locational differences between areas influenced by word labels and olfactory inputs.
These results suggest that multi-voxel patterns of piriform activity can be modulated by semantic context, possibly due to communication between the piriform cortex and the semantic and memory regions.
