title: Cortical activation during fast repetitive finger movements in humans: steady-state movement-related magnetic fields and their cortical generators.
abstract: OBJECTIVE
  To study the cortical physiology of fast repetitive finger movements.
  
  
  METHODS
  We recorded steady-state movement-related magnetic fields (ssMRMFs) associated with self-paced, repetitive, 2-Hz finger movements in a 122-channel whole-head magnetometer. The ssMRMF generators were determined by equivalent current dipole (ECD) modeling and co-registered with anatomical magnetic resonance images (MRIs).
  
  
  RESULTS
  Two major ssMRMF components occurred in proximity to EMG onset: a motor field (MF) peaking at 37+/-11 ms after EMG onset, and a postmovement field (post-MF), with inverse polarity, peaking at 102+/-13 ms after EMG onset. The ECD for the MF was located in the primary motor cortex (M1), and the ECD for the post-MF in the primary somatosensory cortex (S1). The MF was probably closely related to the generation of corticospinal volleys, whereas the post-MF most likely represented reafferent feedback processing.
  
  
  CONCLUSIONS
  The present data offer further evidence that the main phasic changes of cortical activity occur in direct proximity to repetitive EMG bursts in the contralateral M1 and S1. They complement previous electroencephalography (EEG) findings on steady-state movement-related cortical potentials (ssMRCPs) by providing more precise anatomical information, and thereby enhance the potential value of ssMRCPs and ssMRMFs for studying human sensorimotor cortex activation non-invasively and with high temporal resolution.
authors.affiliation: Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1428, USA.
authors.forename: C
authors.initials: C
authors.lastname: Gerloff
authors.forename: N
authors.initials: N
authors.lastname: Uenishi
authors.forename: T
authors.initials: T
authors.lastname: Nagamine
authors.forename: T
authors.initials: T
authors.lastname: Kunieda
authors.forename: M
authors.initials: M
authors.lastname: Hallett
authors.forename: H
authors.initials: H
authors.lastname: Shibasaki
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004569:Electroencephalography; D004576:Electromyography; D005260:Female; D005385:Fingers / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D015225:Magnetoencephalography; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D013933:Thumb / Q000502:physiology; D013997:Time Factors