title: De Novo Emergence of Odor Category Representations in the Human Brain.
abstract: Categorization allows organisms to efficiently extract relevant information from a diverse environment. Because of the multidimensional nature of odor space, this ability is particularly important for the olfactory system. However, categorization relies on experience, and the processes by which the human brain forms categorical representations about new odor percepts are currently unclear. Here we used olfactory psychophysics and multivariate fMRI techniques, in the context of a paired-associates learning task, to examine the emergence of novel odor category representations in the human brain. We found that learning between novel odors and visual category information induces a perceptual reorganization of those odors, in parallel with the emergence of odor category-specific ensemble patterns in perirhinal, orbitofrontal, piriform, and insular cortices. Critically, the learning-induced pattern effects in orbitofrontal and perirhinal cortex predicted the magnitude of categorical learning and perceptual plasticity. The formation of de novo category-specific representations in olfactory and limbic brain regions suggests that such ensemble patterns subserve the development of perceptual classes of information, and imply that these patterns are instrumental to the brain's capacity for odor categorization.
  
  
  CONCLUSIONS
  How the human brain assigns novel odors to perceptual classes and categories is poorly understood. We combined an olfactory-visual paired-associates task with multivariate pattern-based fMRI approaches to investigate the de novo formation of odor category representations within the human brain. The identification of emergent odor category codes within the perirhinal, piriform, orbitofrontal, and insular cortices suggests that these regions can integrate multimodal sensory input to shape category-specific olfactory representations for novel odors, and may ultimately play an important role in assembling each individual's semantic knowledge base of the olfactory world.
authors.affiliation: Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, and lisaqu@u.northwestern.edu j-gottfried@northwestern.edu.
authors.forename: Lisa P
authors.initials: LP
authors.lastname: Qu
authors.affiliation: Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, and.
authors.forename: Thorsten
authors.identifier: http://orcid.org/0000-0002-3575-2670
authors.initials: T
authors.lastname: Kahnt
authors.affiliation: Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, and.
authors.forename: Sydni M
authors.initials: SM
authors.lastname: Cole
authors.affiliation: Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, and Department of Psychology, Northwestern University Weinberg College of Arts and Sciences, Evanston, Illinois 60208 lisaqu@u.northwestern.edu j-gottfried@northwestern.edu.
authors.forename: Jay A
authors.initials: JA
authors.lastname: Gottfried
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D001931:Brain Mapping; D003210:Concept Formation / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007858:Learning / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D009812:Odorants; D009833:Olfactory Pathways / Q000098:blood supply / Q000502:physiology*; D055696:Olfactory Perception / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D015203:Reproducibility of Results; D012119:Respiration; D012903:Smell / Q000502:physiology*; D060388:Support Vector Machine
chemical_list: D010100:Oxygen
keywords: categorization; human; multivariate fMRI; olfaction; perceptual learning