NEUROMAGNETIC LOCALIZATION OF THE LATE COMPONENT OF THE CONTINGENT NEGATIVE-VARIATION

The contingent negative variation (CNV) in a warned choice reaction ti me task was studied in 24 healthy subjects by use of magnetoencephalog raphy (MEG). Special interest was focused on the late component of the CNV, CNVL. Source localization of the magnetically recorded CNVL, mCN V(L) was performed on 13 subjects, selected on the basis of the streng th and stationarity of the electrically recorded CNV, eCNV(L). To achi eve whole head mapping, up to 500 epochs from different scalp position s were recorded, including a pretrial learning period of 40 epochs. Th e neuromagnetic signals studied in this experimental protocol are thus related to neurological processes that are present after an initial l earning period has occurred. In 11 subjects, a goodness of fit between 88% and 95% was achieved using a two-dipole model with one equivalent source localized close to the precentral cortex contralateral to the side of movement, at mean a depth of 30 mm. Estimates of ipsilateral e quivalent sources were less consistent across subjects. In 9 subjects the estimated ipsilateral sources were located symmetrically to the co ntralateral source. The results of this study suggest that the dominan t source of the mCNV(L) is located near the bottom of the sulcus prece ntralis at the anterior bank of the gyrus precentralis, close to the s ulcus frontalis superior. This supports previous findings that the CNV L is closely related to the readiness potential, and that the major co rtical activity is symmetrically located in the left and right premoto r areas.