title: Mirror Motor Activity During Right-Hand Contractions and Its Relation to White Matter in the Posterior Midbody of the Corpus Callosum.
abstract: Cortical activity during simple unimanual actions is typically lateralized to contralateral sensorimotor areas, while a more bilateral pattern is observed with an increase in task demands. In parallel, increasing task demands are associated with subtle mirror muscle activity in the resting hand, implying a relative loss in motor selectivity. The corpus callosum (CC) is crucially involved in unimanual tasks by mediating both facilitatory and inhibitory interactions between bilateral motor cortical systems, but its association with mirror motor activity is yet unknown. Here, we used diffusion-weighted imaging and bilateral electromyographic (EMG) measurements during a unimanual task to investigate potential relationships between white matter microstructure of the CC and mirror EMG activity. Participants performed an unimanual pinch force task with both hands alternatively. Four parametrically increasing force levels were exerted while EMG activity was recorded bilaterally from first dorsal interosseus muscles. Consistent with previous findings, mirror EMG activity increased as a function of force. Additionally, there was a significant relationship between the slope of increasing mirror EMG during right-hand contractions and fractional anisotropy in transcallosal fibers connecting both M1. No significant relationships were found for fibers connecting dorsal premotor cortices or supplementary motor area, indicating the local specificity of the observed brain-physiology relationship.
authors.affiliation: Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig 04103, Germany.|Clinic for Cognitive Neurology, University of Leipzig, Leipzig 04103, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Sehm
authors.affiliation: Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig 04103, Germany.
authors.forename: Christoper J
authors.initials: CJ
authors.lastname: Steele
authors.affiliation: Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig 04103, Germany.|Clinic for Cognitive Neurology, University of Leipzig, Leipzig 04103, Germany.
authors.forename: Arno
authors.initials: A
authors.lastname: Villringer
authors.affiliation: Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig 04103, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ragert
mesh_terms: D000328:Adult; D016880:Anisotropy; D003337:Corpus Callosum / Q000033:anatomy & histology* / Q000502:physiology; D038524:Diffusion Magnetic Resonance Imaging; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D066127:White Matter / Q000502:physiology*
keywords: dorsal premotor cortex; mirror EMG activity; motor overflow; primary motor cortex; supplementary motor area