MICROSTATES IN LANGUAGE-RELATED BRAIN POTENTIAL MAPS SHOW NOUN-VERB DIFFERENCES

Brain processing of grammatical word class was studied analyzing event -related potential (ERP) brain fields. Normal subjects observed a rand omized sequence of single German nouns and verbs on a computer screen, while 20-channel ERP field map series were recorded separately for bo th word classes. Spatial microstate analysis was applied, based on the observation that series of ERP maps consist of epochs of quasi-stable map landscapes and based on the rationale that different map land sca pes must have been generated by different neural generators and thus s uggest different brain functions. Space-oriented segmentation of the m ean map series identified nine successive, different functional micros tates, i.e., steps of brain information processing characterized by qu asi-stable map landscapes. In the microstate from 116 to 172 msec, nou n-related maps differed significantly from verb-related maps along the left-right axis. The results indicate that different neural populatio ns represent different grammatical word classes in language processing , in agreement with clinical observations. This word class differentia tion as revealed by the spatial-temporal organization of neural activi ty occurred at a time after word input compatible with speed of readin g. (C) 1996 Academic Press, Inc.