title: Handedness and effective connectivity of the motor system.
abstract: Handedness denotes the individual predisposition to consistently use the left or right hand for most types of skilled movements. A putative neurobiological mechanism for handedness consists in hemisphere-specific differences in network dynamics that govern unimanual movements. We, therefore, used functional magnetic resonance imaging and dynamic causal modeling to investigate effective connectivity between key motor areas during fist closures of the dominant or non-dominant hand performed by 18 right- and 18 left-handers. Handedness was assessed employing the Edinburgh-Handedness-Inventory (EHI). The network of interest consisted of key motor regions in both hemispheres including the primary motor cortex (M1), supplementary motor area (SMA), ventral premotor cortex (PMv), motor putamen (Put) and motor cerebellum (Cb). The connectivity analysis revealed that in right-handed subjects movements of the dominant hand were associated with significantly stronger coupling of contralateral (left, i.e., dominant) SMA with ipsilateral SMA, ipsilateral PMv, contralateral motor putamen and contralateral M1 compared to equivalent connections in left-handers. The degree of handedness as indexed by the individual EHI scores also correlated with coupling parameters of these connections. In contrast, we found no differences between right- and left-handers when testing for the effect of movement speed on effective connectivity. In conclusion, the data show that handedness is associated with differences in effective connectivity within the human motor network with a prominent role of SMA in right-handers. Left-handers featured less asymmetry in effective connectivity implying different hemispheric mechanisms underlying hand motor control compared to right-handers.
authors.affiliation: Neuromodulation & Neurorehabilitation, Max Planck Institute for Neurological Research, 50931 Cologne, Germany.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Pool
authors.affiliation: Neuromodulation & Neurorehabilitation, Max Planck Institute for Neurological Research, 50931 Cologne, Germany.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Rehme
authors.affiliation: Department of Neurology, University of Cologne, 50924 Cologne, Germany; Institute of Neuroscience and Medicine (INM-1, INM-3), Jülich Research Centre, 52428 Jülich, 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; 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: Neuromodulation & Neurorehabilitation, Max Planck Institute for Neurological Research, 50931 Cologne, Germany; Department of Neurology, University of Cologne, 50924 Cologne, Germany; Institute of Neuroscience and Medicine (INM-1, INM-3), Jülich Research Centre, 52428 Jülich, Germany. Electronic address: christian.grefkes@uk-koeln.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Grefkes
mesh_terms: D000328:Adult; D002531:Cerebellum / Q000502:physiology; D004525:Efferent Pathways / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand / Q000294:innervation / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D009044:Motor Cortex / Q000502:physiology; D009068:Movement / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology*; D011699:Putamen / Q000502:physiology; D055815:Young Adult
keywords: Dynamic causal modeling; Left-handers; Motor putamen; Premotor cortex; Right-handers