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The role of piriform associative connections in odor categorization

  1. Xiaojun Bao  Is a corresponding author
  2. Louise LG Raguet
  3. James D Howard
  4. Jay Gottfried
  1. Northwestern University Feinberg School of Medicine, United States
  2. École Normale Supérieure, France
Research Article
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Cite this article as: eLife 2016;5:e13732 doi: 10.7554/eLife.13732


Distributed neural activity patterns are widely proposed to underlie object identification and categorization in the brain. In the olfactory domain, pattern-based representations of odor objects are encoded in piriform cortex. This region receives both afferent and associative inputs, though their relative contributions to odor perception are poorly understood. Here, we combined a placebo-controlled pharmacological fMRI paradigm with multivariate pattern analyses to test the role of associative connections in sustaining olfactory categorical representations. Administration of baclofen, a GABA(B) agonist known to attenuate piriform associative inputs, interfered with within-category pattern separation in piriform cortex, and the magnitude of this drug-induced change predicted perceptual alterations in fine-odor discrimination performance. Comparatively, baclofen reduced pattern separation between odor categories in orbitofrontal cortex, and impeded within-category generalization in hippocampus. Our findings suggest that odor categorization is a dynamic process concurrently engaging stimulus discrimination and generalization at different stages of olfactory information processing, and highlight the importance of associative networks in maintaining categorical boundaries.

Article and author information

Author details

  1. Xiaojun Bao

    Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, United States
    For correspondence
    Competing interests
    The authors declare that no competing interests exist.
  2. Louise LG Raguet

    Department of Biology, École Normale Supérieure, Lyon, France
    Competing interests
    The authors declare that no competing interests exist.
  3. James D Howard

    Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Jay Gottfried

    Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, United States
    Competing interests
    The authors declare that no competing interests exist.


Human subjects: Informed consent was obtained from subjects to participate in this study, which was approved by the Northwestern University Institutional Review Board.

Reviewing Editor

  1. Lila Davachi, New York University, United States

Publication history

  1. Received: December 11, 2015
  2. Accepted: April 27, 2016
  3. Accepted Manuscript published: April 28, 2016 (version 1)
  4. Version of Record published: May 27, 2016 (version 2)
  5. Version of Record updated: June 29, 2016 (version 3)


© 2016, Bao et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.


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