• K L Whitcroft, J Fischer, P Han, C Raue, M Bensafi, V Gudziol, P Andrews, and T Hummel.
• Interdisciplinary Smell and Taste Lab, TU Dresden, Dresden, Germany; UCL Ear Institute, University College London, UK; Centre for the Study of the Senses, Institute of Philosophy, School of Advanced Study, UK; Royal National Throat Nose and Ear Hospital, Department of Rhinology and Facial Plastic Surgery, London, UK. Electronic address: k.whitcroft@gmail.com.
• Neuroscience. 2018 Dec 15; 395: 22-34.

AbstractFunctional plasticity of the adult brain is well established. Recently, the structural counterpart to such plasticity has been suggested by neuroimaging studies showing experience-dependent differences in gray matter (GM) volumes. Within the primary and secondary olfactory cortices, reduced GM volumes have been demonstrated in patients with olfactory loss. However, these cross-sectional studies do not provide causal evidence for GM volume change, and thereby structural plasticity. Disorders of the peripheral olfactory system, such as chronic rhinosinusitis (CRS), provide an ideal model to study GM structural plasticity, given that patients may experience long periods of olfactory impairment, followed by near complete recovery with treatment. We therefore performed a prospective longitudinal study in patients undergoing surgical treatment for CRS. We used voxel-based morphometry (VBM) to investigate GM volume change in 12 patients (M:F = 7:5; 47.2 ± 14.9 years), 3 months post-op. There was a significant improvement in olfactory function according to birhinal psychophysical testing. We performed a voxel-wise region of interest analysis, with significance corrected for number of regions (p < 0.0036corr). We found significantly increased post-operative GM volumes within the primary (left piriform cortex, right amygdala) and secondary (right orbitofrontal cortex, caudate nucleus, hippocampal-parahippocampal complex and bilateral temporal poles) olfactory networks, and decreased GM volumes within the secondary network only (left caudate nucleus and temporal pole, bilateral hippocampal-parahippocampal complex). As a control measure, we assessed GM change within V1, S1 and A1, where there were no suprathreshold voxels. To our knowledge, this is the first study to demonstrate GM structural plasticity within the primary and secondary olfactory cortices, following restoration of olfaction.Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.

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