Abstract
Higher brain functions were investigated by using electroencephalographic (EEG) and magnetoencephalographic (MEG) techniques. We observed verbal cognitive activities by measuring the EEG and MEG evoked by visually cognitive tasks. English words, meaningless sets of letters, and simple flashes were presented. We analyzed the EEG and MEG data, using a subtraction technique and topographic maps. Visually evoked potentials (VEPs) associated with cognition of meanings were obtained by subtracting VEPs evoked by random letters from VEPs evoked by English words. The topographic EEG maps in several subjects show a clear interhemispheric difference between latencies of 300 and 600 ms. The EEG maps in some subjects, however, show no interhemispheric differences.
