Speech comprehension in noisy environments: Evidence from the predictability effects on the N400 and LPC

Cheng-Hung Hsin; Pei-Chun Chao; Chia-Ying Lee

doi:10.3389/fpsyg.2023.1105346

Speech comprehension in noisy environments: Evidence from the predictability effects on the N400 and LPC

Front Psychol. 2023 Feb 15:14:1105346. doi: 10.3389/fpsyg.2023.1105346. eCollection 2023.

Authors

Cheng-Hung Hsin^{1

2

3}, Pei-Chun Chao², Chia-Ying Lee^{2

4

5}

Affiliations

¹ Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Yang Ming Chiao Tung University and Academia Sinica, Taipei, Taiwan.
² Brain and Language Laboratory, Institute of Linguistics, Academia Sinica, Taipei, Taiwan.
³ Biomedical Acoustic Signal Processing Lab, Research Center for Information Technology Innovation, Academia Sinica, Taipei, Taiwan.
⁴ Institute of Cognitive Neuroscience, National Central University, Taoyuan, Taiwan.
⁵ Research Center for Mind, Brain, and Learning, National Chengchi University, Taipei, Taiwan.

Abstract

Introduction: Speech comprehension involves context-based lexical predictions for efficient semantic integration. This study investigated how noise affects the predictability effect on event-related potentials (ERPs) such as the N400 and late positive component (LPC) in speech comprehension.

Methods: Twenty-seven listeners were asked to comprehend sentences in clear and noisy conditions (hereinafter referred to as "clear speech" and "noisy speech," respectively) that ended with a high-or low-predictability word during electroencephalogram (EEG) recordings.

Results: The study results regarding clear speech showed the predictability effect on the N400, wherein low-predictability words elicited a larger N400 amplitude than did high-predictability words in the centroparietal and frontocentral regions. Noisy speech showed a reduced and delayed predictability effect on the N400 in the centroparietal regions. Additionally, noisy speech showed a predictability effect on the LPC in the centroparietal regions.

Discussion: These findings suggest that listeners achieve comprehension outcomes through different neural mechanisms according to listening conditions. Noisy speech may be comprehended with a second-pass process that possibly functions to recover the phonological form of degraded speech through phonetic reanalysis or repair, thus compensating for decreased predictive efficiency.

Keywords: LPC; N400; event-related potentials; noise; predictability effect; predictive processing; speech comprehension.