Lateralization of the Processing of Semantic Information: An MEG Study of Word Priming

Abstract

Magnetoencephalography was used to study interhemisphere asymmetry of word priming in the window of the N400 semantic component in a group of 28 healthy, right-handed subjects. The overall effects of activation of the “semantic” neural networks in the left and right hemispheres of the brain were evaluated in terms of the total power of responses to sensors (root mean square, RMS) as an analog of the global power field in the EEG. The main results of this study provide evidence that “new” (i.e., not previously encountered in the context of the experiment) words evoked asymmetrical left-hemisphere responses in the window of the N400 component. Repetition of words presented for memorization led to a drop in the amplitude of the “semantic” component in the left hemisphere and was accompanied by a decrease in left-hemisphere asymmetry. The index of differential asymmetry, which considers changes in asymmetry associated with implicit memorization of words, was lateralized to the left hemisphere in most subjects. Differences in the magnitude of asymmetry were related to the level of success of implicit remembering, indicating that it is functional in nature, i.e., it interacts with word memory processes.