Changes in movement-related brain activity during transient deafferentation: a neuromagnetic study

Neuromagnetic fields from the left cerebral hemisphere of three healthy, right-handed subjects were investigated preceding and during voluntary index finger movements performed every 8-15 s under two different experimental conditions: before (stage A) and during (stage B) anesthetic block of median and radial nerves at the wrist. The anesthesia caused blocking of cutaneous receptors and some of the proprioreceptors from a wide hand area, including the entire index finger. However, the index finger movements were not impaired because the muscles participating in the task were not anesthetized. The magnetic signals of the brain sources corresponding to the main components of the movement-related neuromagnetic fields (motor field, MF and movement-evoked field I, MEFI) were mapped and localized using a moving dipole model. In the three investigated subjects the MF and MEFI dipole sources were stronger (30% on average) during stage B than during stage A. No significant changes in spatial coordinates of the estimated dipole locations between stages A and B were observed. This was true for both MF and MEFI. The results show that the MEFI reflects not only proprioceptive input from the periphery but cutaneous inputs as well. In this way the results support the view that cutaneous inputs play a specific role in the cortical control of movement.