Reflection of processing of visually presented verbal stimuli in ERP

The ERPs to familiar, unfamiliar, and recently learned words were recorded in 20 right-handed students who have recently studied a course in sensory physiology during performance of two tasks. The first task consisted in processing of different types of words, the second task required recognition of terms from sensory physiology. In the first task, three types of words were presented to a subject: familiar words related and unrelated to a given category and unfamiliar words. Subjects had to press the appropriate button responding to the questions whether they considered the presented word be related to the given category and whether they were sure in their answer. In the second task, terms from recently studied physiological material were presented to the students who had to detect whether those terms were related or unrelated to the given sensory system. Significant differences between late ERP components were revealed by Student test for matched samples. In the first task, component N400 of the ERP to unfamiliar words was higher than that of the ERP to familiar words. It was also higher in ERPs to words unrelated to the given category than in ERPs to related words. However, this component did not differ between ERPs to well and poorly acquired words in the test on sensory physiology. On the contrary, the late positive component was more expressed in ERPs to familiar and better acquired words in both tasks. Brain mechanisms of processina of different types of words are discussed.