DC-POTENTIALS REVEAL DEVELOPMENTAL-CHANGE S IN CORTICAL ACTIVATION DURING LANGUAGE PROCESSING

The topographical distribution of DC-potentials recorded from the scal p reveals reproductible task-specific patterns of cortical activation during cognition. In order to assess developmental changes in cortical activation related ro language processing, DC-potentials were recorde d in 70 male righthanded subjects aged from 6 to 51 years. Language ta sks required listening to a noun during 2 s and the subsequent mental search for synonyms during 4 s which thereafter were reported. 20 chil dren (age 6-11 years), 20 youths (12-17 years) and 30 adults (18-51 ye ars) were investigated. Electrodes were positioned at bilateral fronta l, central, and parieto-temporal locations using a linked earlobe-refe rence. Search for synonyms caused an increase in surface negative DC-p otential over left frontal brain areas in all subjects. Additional rig ht frontal activation occured only in children. Left frontal lateraliz ation increased with age. The results support the assumption of a prog ressive lateralization during intellectual maturation. According to th is theory, increasing automatization of language processing during dev elopment is accompanied by the focussing of cortical activation to mor e restricted areas of one hemisphere.