Revealing differential importance of word categories in spoken sentence comprehension using phoneme-related...

Background: Verbal communication comprises the retrieval of semantic and syntactic information elicited by various kinds of words (i.e., parts of speech) in a sentence. Content words, such as nouns and verbs, convey essential information about the overall meaning (semantics) of a sentence, whereas function words, such as prepositions and pronouns, carry less meaning and support the syntax of the sentence. Methods: This study aimed to identify neural correlates of the differential information retrieval processes for several parts of speech (i.e., content and function words, nouns and verbs, and objects and subjects) via electroencephalography performed during English spoken-sentence comprehension in thirteen participants with normal hearing. Recently, phoneme-related information has become a potential acoustic feature to investigate human speech processing. Therefore, in this study, we examined the importance of various parts of speech over sentence processing using information about the onset time of phonemes. Results: The distinction in the strength of cortical responses in language-related brain regions provides the neurological evidence that content words, nouns, and objects are dominant compared to function words, verbs, and subjects in spoken sentences, respectively. Conclusions: The findings of this study may provide insights into the different contributions of certain types of words over others to the overall process of sentence understanding.