Odor quality coding and categorization in human posterior piriform cortex

Efficient recognition of odorous objects universally shapes animal behavior and is crucial for survival. To distinguish kin from nonkin, mate from nonmate and food from nonfood, organisms

must be able to create meaningful perceptual representations of odor qualities and categories. It is currently unknown where and in what form the brain encodes information about odor

quality. By combining functional magnetic resonance imaging (fMRI) with multivariate (pattern-based) techniques, we found that spatially distributed ensemble activity in human posterior

piriform cortex (PPC) coincides with perceptual ratings of odor quality, such that odorants with more (or less) similar fMRI patterns were perceived as more (or less) alike. We did not

observe these effects in anterior piriform cortex, amygdala or orbitofrontal cortex, indicating that ensemble coding of odor categorical perception is regionally specific for PPC. These

findings substantiate theoretical models emphasizing the importance of distributed piriform templates for the perceptual reconstruction of odor object quality.

We would like to thank T. Egner, W. Li, J.-P. Magué and T. Parrish for helpful suggestions. This work was supported by grants from the National Institute on Deafness and Other Communication

Disorders to J.A.G. (K08-DC007653 and R01-DC010014).

Cognitive Neurology & Alzheimer's Disease Center, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA

Laboratoire de Neurosciences et Systèmes Sensoriels, Université Claude-Bernard Lyon, Lyon, France

Bernstein Center for Computational Neuroscience, Charité–Universitätsmedizin, Berlin, Germany

Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Department of Neurology, Otto von Guericke University, Magdeburg, Germany

Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA

Department of Psychology, Northwestern University Weinberg College of Arts and Sciences, Evanston, Illinois, USA

J.A.G. conceived the experiment, with contributions and methodological suggestions from J.-D. Haynes. J.D. Howard and J.P. collected the imaging and behavioral data. J.D. Howard, J.P. and

J.A.G. analyzed the data. M.G., J.-D. Haynes and J.D. Howard implemented the flat map analysis. J.A.G., J.D. Howard and J.P. wrote the manuscript.

Supplementary Figures 1–6, Supplementary Table 1, Supplementary Data and Supplementary Discussion (PDF 404 kb)

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