MEntal Representation of ODors: from physical features to perceptual processing
Final Report Abstract
In this series of experiments we explored the two following major aims: (1) we wanted to test how we extract chemical and perceptual similarities among olfactory stimuli. To this end we first set up a database that characterized the perceived characteristics of a large number of chemicals. This database was the used for later experiments where we looked at odor-induced activity at the level of the nose – the olfactory nerves – and the brain. To characterize these activations we used the ratings of participants (e.g., intensity, pleasantness, irritation, familiarity), the electrical signals form the nose, the size of certain brain structures and the changes in neuronal activations in the brain. Further, we studied brain plasticity in healthy individuals (smell and experts and “smell novices”) and patients with autism or patients with olfactory loss to learn more about the effects of exposure to olfactory stimuli. We found that the representation of odors is multidimensional, involving primary sensory areas to process chemical attributes of smells and secondary areas for perceptual features. In certain pathological conditions (characterized by olfactory loss), this representation is significantly altered. However, plasticity mechanisms occur with learning, inducing changes in the organization of this representation at several levels of processing: from the peripheral at the nasal mucosa, the brain primary sensory areas to more associative areas. To our surprise we found that irritation is a major factor in the perception of odors. And we found first signs that the pleasantness of odors is already encoded at the earliest stages of brain processing – at the level of the olfactory bulb. Applications are used in the creation of clinical tests for the assessment of olfactory function, or smell trainings which currently find broad applications in the olfactory loss that affects approximately 2/3 of patients with COVID19. (2) We set out to promote scientific culture and communication on olfaction in the general public and in higher education by providing lectures and practical classes in the University of Lyon and the Technical University of Dresden based on the findings of the project. We believe that we succeeded in that we considerably promoted the significance of olfaction in a large series of presentations, interviews, newspaper articles. Hence, we disseminated our findings to the general public, students, specialist and non-specialist scientists. In this context we especially enjoyed the communication with children in classrooms, museums, and in public events like the long night of research in Dresden. These efforts will continue!
Publications
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(2016) Machine-learned pattern identification in olfactory subtest results. Sci Rep 6:35688
Lotsch j, Hummel T, Ultsch A
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(2017) Learning to name smells increases activity in heteromodal semantic areas. Hum Brain Mapp 38:5958-5969
Fournel A, Sezille C, Licon CC, Sinding C, Gerber J, Ferdenzi C, Hummel T, Bensafi M
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(2017) Olfactory training using heavy and light weight molecule odours. Perception 46:343-351
Poletti SC, Michel E, Hummel T
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(2017) Olfactory training with older people. J Gerontol A Biol Sci Med Sci 72:1072-1079
Wegener BA, Croy I, Hähner A, Hummel T
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(2018) Brain Volume Changes in Hyposmic Patients Before and After Olfactory Training. Laryngoscope 128: 1531-1536
Gellrich J, Manesse C, Han P, Betz A, Junghans A, Raue C, Schriever VA, Hummel T
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(2018) Electro-olfactogram responses before and after aversive olfactory conditioning in humans . Neurosci 373:199-206
Cavazzana A, Poletti SC, Guducu C, Larsson M, Hummel T
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(2018) Impaired Odor Perception in Autism Spectrum Disorder Is Associated with Decreased Activity in Olfactory Cortex. Chem Senses 43:627-634
Koehler L, Fournel A, Albertowski K, Roessner V, Gerber J, Hummel C, Hummel T, Bensafi M
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(2018) Pleasantness and trigeminal sensations as salient dimensions in organizing the semantic and physiological spaces of odors. Sci Rep 8:8444
Licon CC, Manesse C, Dantec M, Fournel A, Bensafi M
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(2018) Structural plasticity of the primary and secondary olfactory cortices: increased grey matter volume following surgical treatment for chronic rhinosinusitis. Neurosci 395:22-34
Whitcroft KL, Fischer J, Han P, Raue C, Bensafi M, Gudziol V, Andrews P, Hummel T
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(2019) Chemical features mining provides new descriptive structure-odor relationships. PLoS Comput Biol 15:e1006945
Licon CC, Bosc G, Sabri M, Mantel M, Fournel A, Bushdid C, Golebiowski J, Robardet C, Plantevit M, Kaytoue M, Bensafi M
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(2020) A Methodological Investigation of a Dental MRI Coil to Obtain Functional Signals from the Human Olfactory Bulb. J Neurosci Meth 335:108624
Fournel A, Iannilli E, Ferdenzi C, Werner A, Hummel T, Bensafi M
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(2020) Neural processing of odor-associated words: an fMRI study in patients with acquired olfactory loss. Brain Imag Behav 14:1164-1174
Han P, Croy I, Raue C, Bensafi M, Larsson M, Cavazzana A, Hummel T
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(2021) Data-science based analysis of perceptual spaces of odors in olfactory loss. Chem Senses
Lötsch J, Ultsch A, Hähner A, Willgeroth V, Bensafi M, Zaliani A, Hummel T
