CHANGES IN MOVEMENT-RELATED BRAIN ACTIVITY DURING TRANSIENT DEAFFERENTATION - A NEUROMAGNETIC STUDY

Neuromagnetic fields from the left cerebral hemisphere of three health y, right-handed subjects were investigated preceding and during volunt ary index finger movements performed every 8-15 s under two different experimental conditions: before (stage A) and during (stage B) anesthe tic block of median and radial nerves at the wrist. The anesthesia cau sed blocking of cutaneous receptors and some of the proprioreceptors f rom a wide hand area, including the entire index finger. However, the index finger movements were not impaired because the muscles participa ting in the task were not anesthetized. The magnetic signals of the br ain sources corresponding to the main components of the movement-relat ed neuromagnetic fields (motor field, MF and movement-evoked field I, MEFI) were mapped and localized using a moving dipole model. In the th ree investigated subjects the MF and MEFI dipole sources were stronger (30% on average) during stage B than during stage A. No significant c hanges in spatial coordinates of the estimated dipole locations betwee n stages A and B were observed. This was true for both MF and MEFI. Th e results show that the MEFI reflects not only proprioceptive input fr om the periphery but cutaneous inputs as well. In this way the results support the view that cutaneous inputs play a specific role in the co rtical control of movement.