Neuroanatomical correlates of olfactory performance
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We investigated associations between olfactory function and gray matter thickness in 46 healthy young subjects by means of an automated technique for measuring cortical thickness. We used an extended version of the Sniffin’ Sticks test to assess olfactory function, including odor threshold, concentration discrimination, quality discrimination, and odor identification. We observed a correlation between olfactory performance and cortical thickness of structures involved in earlier and later stages of chemosensory processing such as right medial orbitofrontal cortex, right insula, and adjacent cortex. Furthermore, we found significant bilateral correlations of olfactory performance with cortical thickness of areas around the central sulcus bilaterally, structures responsible for voluntary respiration and sniffing. In addition to expected general sex effects on cortical thickness, we observed areas, such as the entorhinal cortex, occipital cortex, intraparietal sulcus and insula (all in the right hemisphere), where the correlation between higher order olfactory functions and cortical thickness differed between women and men. These data demonstrate, for some neuroanatomical structures, a link between cortical thickness and olfactory function, in that thicker cortex is usually associated with better performance, but not always. This association between anatomy and olfactory performance suggests a possible biological explanation for the high degree of individual differences and sex effects observed in higher order olfactory tasks.
KeywordsSmell Olfaction Cortical thickness Brain anatomy MRI
We thank Alan Evans, Sylvain Milot, Claude Lepage, Nicolas Guizard, Samir Das, Ilana Leppert and the people from the McConnell Brain Imaging Centre of the Montreal Neurological Institute for the use of and the help with the CIVET data pipeline. We thank Marc Bouffard and Marc Schönwiesner for their suggestions at the data analysis. We thank Monica Hernandez, Giulia DeProphetis, and Aline Gauchat for behavioral testing. This study was supported by operating grant (MOP 57846) awarded to MJG by the Canadian Institutes of Health Research. JF is now supported by the Fondation de Ste.-Justine and the Fondation des Etoiles, JNL is now supported by the NIDCD (R03DC009869). RJZ is supported by the Canadian Institutes of Health Research and the Natural Sciences and Engineering Research Council.
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