title: Olfactory Network Differences in Master Sommeliers: Connectivity Analysis Using Granger Causality and Graph Theoretical Approach.
abstract: Previous studies investigating the differences in olfactory processing and judgments between trained sommeliers and controls have shown increased activations in brain regions involving higher level cognitive processes in sommeliers. However, there is little information about the influence of expertise on causal connectivity and topological properties of the connectivity networks between these regions. Therefore, the current study focuses on addressing these questions in a functional magnetic resonance imaging (fMRI) study of olfactory perception in Master Sommeliers. fMRI data were acquired from Master Sommeliers and control participants during different olfactory and nonolfactory tasks. Mean time series were extracted from 90 different regions of interest (ROIs; based on Automated Anatomical Labeling atlas). The underlying neuronal variables were extracted using blind hemodynamic deconvolution and then input into a dynamic multivariate autoregressive model to obtain connectivity between every pair of ROIs as a function of time. These connectivity values were then statistically compared to obtain paths that were significantly different between the two groups. The obtained connectivity matrices were further studied using graph theoretical methods. In sommeliers, significantly greater connectivity was observed in connections involving the precuneus, caudate, putamen, and several frontal and temporal regions. The controls showed increased connectivity from the left hippocampus to the frontal regions. Furthermore, the sommeliers exhibited significantly higher small-world topology than the controls. These findings are significant, given that learning about neuroplasticity in adulthood in these regions may then have added clinical importance in diseases such as Alzheimer's and Parkinson's where early neurodegeneration is isolated to regions important in smell.
authors.affiliation: 1 Cleveland Clinic Lou Ruvo Center for Brain Health, Las Vegas, Nevada.
authors.forename: Karthik
authors.initials: K
authors.lastname: Sreenivasan
authors.affiliation: 1 Cleveland Clinic Lou Ruvo Center for Brain Health, Las Vegas, Nevada.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhuang
authors.affiliation: 1 Cleveland Clinic Lou Ruvo Center for Brain Health, Las Vegas, Nevada.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Banks
authors.affiliation: 1 Cleveland Clinic Lou Ruvo Center for Brain Health, Las Vegas, Nevada.
authors.forename: Virendra
authors.initials: V
authors.lastname: Mishra
authors.affiliation: 1 Cleveland Clinic Lou Ruvo Center for Brain Health, Las Vegas, Nevada.
authors.forename: Zhengshi
authors.initials: Z
authors.lastname: Yang
authors.affiliation: 2 Department of Electrical and Computer Engineering, AU MRI Research Center, Auburn University , Auburn, Alabama.|3 Department of Psychology, Auburn University , Auburn, Alabama.|4 Alabama Advanced Imaging Consortium, Auburn University and University of Alabama Birmingham , Birmingham, Alabama.
authors.forename: Gopikrishna
authors.initials: G
authors.lastname: Deshpande
authors.affiliation: 1 Cleveland Clinic Lou Ruvo Center for Brain Health, Las Vegas, Nevada.|5 Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Cordes
mesh_terms: D000328:Adult; D001931:Brain Mapping; D003463:Cues; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009833:Olfactory Pathways / Q000000981:diagnostic imaging* / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010296:Parietal Lobe / Q000000981:diagnostic imaging*; D010775:Photic Stimulation; D011361:Professional Competence; D011930:Reaction Time; D012903:Smell / Q000502:physiology*
chemical_list: D010100:Oxygen
keywords: Granger causality; effective connectivity; experts; functional magnetic resonance imaging; graph theory; olfaction