title: Reappraisal of field dynamics of motor cortex during self-paced finger movements.
abstract: BACKGROUND
  The exact origin of neuronal responses in the human sensorimotor cortex subserving the generation of voluntary movements remains unclear, despite the presence of characteristic but robust waveforms in the records of electroencephalography or magnetoencephalography (MEG).
  
  
  OBJECTIVE
  To clarify this fundamental and important problem, we analyzed MEG in more detail using a multidipole model during pulsatile extension of the index finger, and made some important new findings.
  
  
  RESULTS
  Movement-related cerebral fields (MRCFs) were confirmed over the sensorimotor region contralateral to the movement, consisting of a temporal succession of the first premovement component termed motor field, followed by two or three postmovement components termed movement evoked fields. A source analysis was applied to separately model each of these field components. Equivalent current diploes of all components of MRCFs were estimated to be located in the same precentral motor region, and did not differ with respect to their locations and orientations. The somatosensory evoked fields following median nerve stimulation were used to validate these findings through comparisons of the location and orientation of composite sources with those specified in MRCFs. The sources for the earliest components were evoked in Brodmann's area 3b located lateral to the sources of MRCFs, and those for subsequent components in area 5 and the secondary somatosensory area were located posterior to and inferior to the sources of MRCFs, respectively. Another component peaking at a comparable latency with the area 3b source was identified in the precentral motor region where all sources of MRCFs were located.
  
  
  CONCLUSIONS
  These results suggest that the MRCF waveform reflects a series of responses originating in the precentral motor area.
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences Okazaki, 444-8585, Japan ; Department of Psychology, Kinjo Gakuin University Omori 2-1723 Moriyama, Nagoya, 463-8521, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences Okazaki, 444-8585, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Wasaka
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences Okazaki, 444-8585, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Inui
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences Okazaki, 444-8585, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kakigi
keywords: Diploe sources; magnetoencephalography; motor cortex; movement-related cerebral fields; somatosensory evoked fields