Objectives: Event-related potential correlates of phonological encoding - as compared with lexical access and semantic categorization - were measured in two studies involving two groups of 14 German and 14 Italian subjects.
Methods: A two stimulus reaction time paradigm was used. Stimulus pairs presented one-by-one with 2 s inter-stimulus intervals (ISI) had to be matched with respect to lexical identity (word-picture) in a word comprehension task or with respect to the phonological representative of objects in a rhyming task. A semantic categorization task was added for the Italian sample. In both studies, the EEG was recorded from 26 scalp electrodes according to the 10-20 system. The slow negative potential during the ISI (CNV) was determined as the electrocortical correlate of preparation for and activation of the specific language-related task.
Results: In both samples, phonological encoding (rhyming) evoked a more pronounced CNV over the left- compared with the right-frontal area, while less lateralized central dominance of the CNV was found in the word comprehension task. Semantic categorization was accompanied by the least asymmetry of activity.
Conclusions: Results indicate that the different degree of asymmetry induced by phonological and semantic processing may be determined from the scalp distribution of slow cortical potentials with cross-lingual reliability.