Processing Metrical Information in Silent Reading: An ERP Study.

Olga Kriukova,Nivedita Mani

doi:10.3389/fpsyg.2016.01432

Abstract

Listeners are sensitive to the metric structure of words, i.e., an alternating pattern of stressed and unstressed syllables, in auditory speech processing: Event-related potentials recorded as participants listen to a sequence of words with a consistent metrical pattern, e.g., a series of trochaic words, suggest that participants register words metrically incongruent with the preceding sequence. Here we examine whether the processing of individual words in silent reading is similarly impacted by rhythmic properties of the surrounding context. We recorded participants’ EEG as they read lists of either three trochaic or iambic disyllabic words followed by a target word that was either congruent or incongruent with the preceding metric pattern. Event-Related Potentials (ERPs) to targets were modulated by an interaction between metrical structure (iambic vs. trochaic) and congruence: for iambs, more positive ERPs were observed in the incongruent than congruent condition 250–400 ms and 400–600 ms post-stimulus, whereas no reliable impact of congruence was found for trochees. We suggest that when iambs are in an incongruent context, i.e., preceded by trochees, the context contains the metrical structure that is more typical in participants’ native language which facilitates processing relative to when they are presented in a congruent context, containing the less typical, i.e., iambic, metrical structure. The results provide evidence that comprehenders are sensitive to the prosodic properties of the context even in silent reading, such that this sensitivity impacts lexico-semantic processing of individual words.

Highlights

Metrical stress, patterns of alternations of strong and weak syllables in polysyllabic words, phrases, or sentences, is an important characteristic of spoken language
To evaluate the results statistically, separate four-way ANOVAs with withinsubject factors Meter, Congruence, Location and Laterality of the electrode were conducted on the mean voltages evoked by targets in the 250–400 ms (N325), 400–600 ms (N400), and 600–799 ms time windows
The analyses focused on the two components previously observed in the literature: the N325, a component known to be sensitive to metrical properties in spoken language processing (Böcker et al, 1999; Rothermich et al, 2010) and the N400, a component related to lexico-semantic processing but shown to vary as a function of metrical characteristics of speech (Böcker et al, 1999; Knaus et al, 2007)

Summary

Introduction

Patterns of alternations of strong and weak syllables in polysyllabic words, phrases, or sentences, is an important characteristic of spoken language. Given the functional importance of metrical stress for speech processing, it is not surprising that listeners register metrical regularities and inconsistencies even without explicit instructions to do so. Another study by Böcker et al (1999) presented participants with sequences of four disyllabic Dutch words where the last word either followed the same metrical pattern as the preceding words or deviated from it. They observed an event-related potential (ERP) component they termed the N325, which was sensitive to both metrical congruence and structure processing. The findings of Böcker et al (1999). indicated that there may be an independent cognitive process of registering metrical properties of speech (both rhythmic incongruities and metrical typicality) that at later stages interferes with lexicosemantic processing

Methods

Results

Conclusion