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A neural electrophysiological study of lexical stress parsing

By Ying Yang

Abstract

Based on past theory and empirical results on the processing of lexical-level suprasegmental information, a Cascading Inhibition model for lexical stress parsing was proposed, in which lexical stress is situated at a different level from segmental information in a hierarchical structure and influences lexical identification via two mediating levels. These levels were proposed to direct lexical identification in a parallel and statistical manner. \ud \ud Because under this model, phonetic and lexical processing are both under the influence of lexical stress parsing, and because pre-attentive phonetic and lexical processing are both lateralized to the left hemisphere, two hypotheses were proposed: Hypothesis A: Lexical stress parsing can modulate lexical selection without the presence of segmental information; Hypothesis B: Lexical stress parsing is lateralized to the left hemisphere. \ud \ud To test these hypotheses, Noun-Verb homonym pairs (e.g. INsult vs inSULT) were used as targets in experimental listening conditions. Sentences that strongly predicted the Noun member (e.g. INsult) of the pair were spliced to end with the Verb member (e.g. inSULT) to create lexical stress anomalies. In the critical conditions, when targets were low-pass filtered to remove segmental information, listeners had to rely on the Lexical Stress Pattern for lexical identification of the target. For control conditions, the prosody changes associated with a shift in sex of the speaker (Gender Shift) were investigated in an auditory oddball paradigm. It was predicted that processing nonlinguistic prosody such as Gender Shift, in contrast to lexical stress, would be lateralized to the right hemisphere. \ud \ud Online EEG was recorded from right-handed young normal monolingual English speakers. For experimental conditions, the filtered Verb Lexical Stress Pattern induced larger N400 than filtered Noun Lexical Stress Pattern, and this component was left-lateralized, supporting both hypotheses. Global Field Power and source estimation demonstrated that the neural networks for parsing Lexical Stress Pattern were similar to those for processing segmental information. In control conditions, the P300 induced by Gender Shift was right lateralized. Overall, many features of the CI model were supported, but a direct influence from the prosody level to the lexical identification level is proposed to incorporate results from the current study. \u

Year: 2013
OAI identifier: oai:d-scholarship.pitt.edu:15562
Provided by: D-Scholarship@Pitt

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