Prosody-driven Sentence Processing: An Event-related Brain Potential Study

Four experiments systematically investigating the brain's response to the perception of sentences containing differing amounts of linguistic information are presented. Spoken language generally provides various levels of information for the interpretation of the incoming speech stream. Here, we focus on the processing of prosodic phrasing, especially on its interplay with phonemic, semantic, and syntactic information. An event-related brain potential (ERP) paradigm was chosen to record the on-line responses to the processing of sentences containing major prosodic boundaries. For the perception of these prosodic boundaries, the so-called closure positive shift (CPS) has been manifested as a reliable and replicable ERP component. It has mainly been shown to correlate to major intonational phrasing in spoken language. However, to define this component as exclusively relying on the prosodic information in the speech stream, it is necessary to systematically reduce the linguistic content of the stimulus material. This was done by creating quasi-natural sentence material with decreasing semantic, syntactic, and phonemic information (i.e., jabberwocky sentences, in which all content words were replaced by meaningless words; pseudoword sentences, in which all function and all content words are replaced by meaningless words; and delexicalized sentences, hummed intonation contour of a sentence removing all segmental content). The finding that a CPS was identified in all sentence types in correlation to the perception of their major intonational boundaries clearly indicates that this effect is driven purely by prosody.