[Verbal stimuli semantics and relevance of ERPs]

In 22 healthy participants EEG from 28 channels was recorded during visual presentation of a random sequence of words and pseudo-words. The experiment consisted of three parts. In the first part the subjects just passively read the stimuli, in the second part they had to click the mouse button when seeing a word and in the third part--when seeing a pseudo-word. The results show that words are more significant to subjects than pseudo-words causing higher amplitude of P100 and P300 in the first and the second parts of the experiment, evidently, due to presence of meaning. However, the lexical task may be a more significant factor of the information processing than the presence of meaning, since in the third part of the experiment, where pseudo-words were relevant, they elicited higher amplitude of P300 than words. Pseudo-words elicited also negative N400 amplitude than words, revealing incongruity effect. However, when words were task-incongruent, this effect is significantly less evident.