title: Functional resting-state connectivity of the human motor network: differences between right- and left-handers.
abstract: Handedness is associated with differences in activation levels in various motor tasks performed with the dominant or non-dominant hand. Here we tested whether handedness is reflected in the functional architecture of the motor system even in the absence of an overt motor task. Using resting-state functional magnetic resonance imaging we investigated 18 right- and 18 left-handers. Whole-brain functional connectivity maps of the primary motor cortex (M1), supplementary motor area (SMA), dorsolateral premotor cortex (PMd), pre-SMA, inferior frontal junction and motor putamen were compared between right- and left-handers. We further used a multivariate linear support vector machine (SVM) classifier to reveal the specificity of brain regions for classifying handedness based on individual resting-state maps. Using left M1 as seed region, functional connectivity analysis revealed stronger interhemispheric functional connectivity between left M1 and right PMd in right-handers as compared to left-handers. This connectivity cluster contributed to the individual classification of right- and left-handers with 86.2% accuracy. Consistently, also seeding from right PMd yielded a similar handedness-dependent effect in left M1, albeit with lower classification accuracy (78.1%). Control analyses of the other resting-state networks including the speech and the visual network revealed no significant differences in functional connectivity related to handedness. In conclusion, our data revealed an intrinsically higher functional connectivity in right-handers. These results may help to explain that hand preference is more lateralized in right-handers than in left-handers. Furthermore, enhanced functional connectivity between left M1 and right PMd may serve as an individual marker of handedness.
authors.affiliation: Institute of Neuroscience and Medicine (INM-1, INM-3), Jülich Research Centre, 52428 Jülich, Germany; Department of Neurology, University of Cologne, 50931 Cologne, Germany.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Pool
authors.affiliation: Institute of Neuroscience and Medicine (INM-1, INM-3), Jülich Research Centre, 52428 Jülich, Germany; Department of Neurology, University of Cologne, 50931 Cologne, Germany.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Rehme
authors.affiliation: Department of Neurology, University of Cologne, 50931 Cologne, Germany; Institute of Clinical Neuroscience and Medical Psychology, Heinrich Heine University, 40225 Düsseldorf, Germany.
authors.forename: Simon B
authors.initials: SB
authors.lastname: Eickhoff
authors.affiliation: Institute of Neuroscience and Medicine (INM-1, INM-3), Jülich Research Centre, 52428 Jülich, Germany; Department of Neurology, University of Cologne, 50931 Cologne, Germany.
authors.forename: Gereon R
authors.initials: GR
authors.lastname: Fink
authors.affiliation: Institute of Neuroscience and Medicine (INM-1, INM-3), Jülich Research Centre, 52428 Jülich, Germany; Department of Neurology, University of Cologne, 50931 Cologne, Germany. Electronic address: christian.grefkes@uk-koeln.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Grefkes
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007206:Individuality; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D060388:Support Vector Machine; D055815:Young Adult
keywords: Dorsolateral premotor cortex; Handedness; Inferior frontal gyrus; Motor asymmetry; Support vector machine