Bilateral activation of the human somatomotor cortex by distal hand movements

Electroencephalogr Clin Neurophysiol. 1995 Dec;95(6):444-52. doi: 10.1016/0013-4694(95)00193-x.


We recorded cortical magnetic signals, simultaneously over the whole scalp, from 6 healthy subjects during 3 motor tasks to track the varying proportion of contra- vs. ipsilateral activation. The subjects performed self-paced index finger flexions, simultaneous flexion of 4 fingers, and a sequence of rapid digit movements in different sessions. Index finger and 4-finger movements were associated with phasic bilateral dampening of spontaneous 10 and 20 Hz rhythms along the central sulcus, starting approximately 1 sec before the movement in the contralateral hemisphere. A rebound occurred within 1 sec after the index finger and 4-finger flexions; the rapid finger movements resulted in a persistent blocking of the rhythms. Averaging with respect to movement onset showed a slow bilateral frontal readiness field starting about 0.5 sec prior to motion onset. It was followed, within 200 msec after movement onset, by phasic movement-evoked fields (MEFs) which were bilateral during the tasks involving several fingers. The contra- vs. ipsilateral MEF amplitude ratio C/I decreased from 4.0 during index finger movements to 0.6 during rapid finger flexions, reflecting the enhanced activation of the ipsilateral primary somatomotor cortex with increasing complexity of movement.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Brain Mapping
  • Evoked Potentials / physiology
  • Female
  • Functional Laterality / physiology
  • Hand / physiology
  • Humans
  • Magnetoencephalography
  • Male
  • Motor Cortex / physiology*
  • Movement / physiology*
  • Reaction Time / physiology
  • Somatosensory Cortex / physiology*