Scientists reveal chemical structural analysis in neural computations that allow us to identify odors
Mar 2024, phys.org
via Institute of Psychology of the Chinese Academy of Sciences: Yuting Ye et al, Decomposition of an odorant in olfactory perception and neural representation, Nature Human Behaviour (2024). DOI: 10.1038/s41562-024-01849-0
Image credit: name that facial feature: AI Art - Mature Woman Applying Regenerating Serum in Italian - 2025
Name that odor: Identical odors seem different when given different names
May 2024, phys.org
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."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.
via University of Tokyo: Toshiki Okumura et al, Semantic context‐dependent neural representations of odors in the human piriform cortex revealed by 7T MRI, Human Brain Mapping (2024). DOI: 10.1002/hbm.26681
Detecting odors on the edge: Researchers decipher how insects smell more with less
May 2024, phys.org
Wiring diagram of the fly nose; and since olfaction is the ideal model for how the brain works, because of its severe simplicity -Previous investigations of the odor processing system in flies focused on the central brain as the main hub for processing odor signals. But the new study shows that the effectiveness of the insect's sensory capabilities relies on a "pre-processing" stage in the periphery of their sensory system, which prepares the odor signals for computations that occur later in the central brain region.Flies smell through their antennae, which are replete with sensory hairs that detect elements of the environment around them. Each sensory hair usually features two olfactory receptor neurons. "The signals carried by the wires interfere with each other through electromagnetic interactions," and helps flies quickly compute the "gist" of the odor's meaning."Remarkably, our work shows that the optimal odor blend—the precise ratio to which each sensory hair is most sensitive—is defined by the genetically predetermined size difference between the coupled olfactory neurons," said Aljadeff, a faculty member in the School of Biological Sciences. "Our work highlights the far-reaching algorithmic role of the sensory periphery for the processing of both innately meaningful and learned odors in the central brain."
via University of California San Diego: Palka Puri et al, Peripheral preprocessing in Drosophila facilitates odor classification, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2316799121
Another step towards decoding smell: Investigating the neuronal mechanisms of human odor perception
Oct 2024, phys.org
Yes, thank you once again, epilepsy:The research group has now succeeded for the first time in recording the activity of individual nerve cells during smelling, by monitoring epilepsy patients.While the activity of nerve cells in the olfactory cortex most accurately predicted which scent was smelled, neuronal activity in the hippocampus was able to predict whether scents were correctly identified. Only nerve cells in the amygdala, a region involved in emotional processing, reacted differently depending on whether a scent was perceived as pleasant or unpleasant.In a next step, the researchers investigated the connection between the perception of scents and images. To do this, they presented the participants in the Bonn study with the matching images for each odor, for example, the scent and later a photo of a banana, and examined the reaction of the neurons. Surprisingly, nerve cells in the primary olfactory cortex responded not only to scents, but also to images.
via Department of Epileptology at University Hospital of Bonn: Marcel S. Kehl et al, Single-neuron representations of odours in the human brain, Nature (2024). DOI: 10.1038/s41586-024-08016-5
Humans can distinguish odors with millisecond precision
Oct 2024, phys.org
Human olfactory perception can detect fine chemical changes within the duration of a single sniff.A unique sniff-triggered device that controls odor delivery with a precision of 18 milliseconds created temporal odor mixtures, presenting two odors one after the other, tested with 229 participants across five experiments to see if they could distinguish these mixtures.When two odor compounds, A and B, were presented in different orders, participants could tell the difference when the delay between the compounds was just 60 milliseconds.
via Institute of Psychology of the Chinese Academy of Sciences: Wen Zhou, Human olfactory perception embeds fine temporal resolution within a single sniff, Nature Human Behaviour (2024). DOI: 10.1038/s41562-024-01984-8.
