Abstract: Prosodic boundary, as an integral part of prosodic features in spoken language, is very important in sentence and discourse comprehension. Recently, researchers have shown increasing interest in the neural mechanism of prosodic boundary processing.
Numerous studies have found that CPS, a special ERP component reflecting the closure of phonological phrase, could be induced by phonological phrase boundary embedded in a sentence. Also, researches have demonstrated that intonational phrase boundary in the end of a sentence consistently elicited P3, which reflects the operation of “syntactic closure” as well as the completeness of language unit. The present study aims to investigate the cognitive processing of intonational phrase boundary embedded in discourse and its related brain effect using ERP.
To explore the processing of intonational phrase boundary in discourse, quatrain was used, which is composed of four sentences and five or seven characters in each sentence. Twenty (10 males) healthy undergraduates participated in the experiment. The participants were told to listen carefully to each poem, and complete a word discrimination task. Specifically, if the word "Space" was presented, they were asked to press the spacebar to continue. If other words were presented, they were required to press the "F" or "J" key to indicate whether the word appeared in the poem they had just heard. The EEG was recorded from 64 scalp channels using electrodes mounted in an elastic cap. Boundary-related ERPs were calculated for a 1500 ms epoch including a 200 ms pre-boundary syllable baseline.
It was found that the three intonational phrase boundaries embedded in the quatrain elicited CPS respectively, with no differences in time course, amplitude and scalp distribution, indicating that prosodic boundary processing was not influenced by its position in discourse. Moreover, the final sentence of both five-character-quatrain and seven-character-quatrain evoked the P3 effect, with the amplitude elicited by the former one lower than that of the later one, but no differences in scalp distribution and onset latency.
The present study suggests that boundaries conveying both the closure of preceding information and the prediction of upcoming information will induce CPS, while boundaries reflecting only the closure of preceding information will elicit P3. The nature and characteristics of these two components were also discussed in the present study.

Key words: prosodic boundary, P3, closure positive shift