Exploring N400 Predictability Effects During Sustained Speech Comprehension: From Listening-Related Fatigue to Speech Enhancement Evaluation.

IF 2.6 2区 医学 Q1 AUDIOLOGY & SPEECH-LANGUAGE PATHOLOGY
Cheng-Hung Hsin, Chia-Ying Lee, Yu Tsao
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Abstract

Objectives: This study investigated the predictability effect on the N400 as an objective measure of listening-related fatigue during speech comprehension by: (1) examining how its characteristics (amplitude, latency, and topographic distribution) changed over time under clear versus noisy conditions to assess its utility as a marker for listening-related fatigue, and (2) evaluating whether these N400 parameters could assess the effectiveness of speech enhancement (SE) systems.

Design: Two event-related potential experiments were conducted on 140 young adults (aged 20 to 30) assigned to four age-matched groups. Using a between-subjects design for listening conditions, participants comprehended spoken sentences ending in high- or low-predictability words while their brain activity was recorded using electroencephalography. Experiment 1 compared the predictability effect on the N400 in clear and noise-masked conditions, while experiment 2 examined this effect under two enhanced conditions (denoised using the transformer- and minimum mean square error-based SE models). Electroencephalography data were divided into two blocks to analyze the changes in the predictability effect on the N400 over time, including amplitude, latency, and topographic distributions.

Results: Experiment 1 compared N400 effects across blocks under different clarity conditions. Clear speech in block 2 elicited a more anteriorly distributed N400 effect without reduction or delay compared with block 1. Noisy speech in block 2 showed a reduced, delayed, and posteriorly distributed effect compared with block 1. Experiment 2 examined N400 effects during enhanced speech processing. Transformer-enhanced speech in block 1 demonstrated significantly increased N400 effect amplitude compared to noisy speech. However, both enhancement methods showed delayed N400 effects in block 2.

Conclusions: This study suggests that temporal changes in the N400 predictability effect might serve as objective markers of sustained speech processing under different clarity conditions. During clear speech comprehension, listeners appear to maintain efficient semantic processing through additional resource recruitment over time, while noisy speech leads to reduced processing efficiency. When applied to enhanced speech, these N400 patterns reveal both the immediate benefits of SE for semantic processing and potential limitations in supporting sustained listening. These findings demonstrate the potential utility of the N400 predictability effect for understanding sustained listening demands and evaluating SE effectiveness.

探索N400可预测性对持续语音理解的影响:从听力相关疲劳到语音增强评价。
目的:本研究考察了N400作为语音理解过程中听力相关疲劳的客观测量指标的可预测性影响:(1)研究了其特征(振幅、潜伏期和地形分布)在清晰和嘈杂条件下随时间的变化,以评估其作为听力相关疲劳标志的效用;(2)评估这些N400参数是否可以评估语音增强(SE)系统的有效性。设计:140名年轻人(20 - 30岁)被分为4个年龄匹配组,进行了两个事件相关电位实验。在听力条件下,使用受试者间设计,参与者理解以高或低可预测性单词结尾的口语句子,同时使用脑电图记录他们的大脑活动。实验1比较了在清晰和噪声屏蔽条件下的可预测性对N400的影响,而实验2在两种增强条件下(使用基于变压器和最小均方误差的SE模型去噪)检验了这种影响。将脑电图数据分成两组,分析N400的可预测性效应随时间的变化,包括振幅、潜伏期和地形分布。结果:实验1比较了不同清晰度条件下N400的跨块效应。与第1块相比,第2块清晰的言语引起了更前分布的N400效应,没有减少或延迟。与块1相比,块2中有噪声的语音表现出减少、延迟和后分布的效果。实验2考察了N400在增强语音处理中的作用。与有噪声的语音相比,block 1中变压器增强语音的N400效应幅度显著增加。然而,两种增强方法在block 2中都表现出延迟的N400效应。结论:本研究提示N400可预测性效应的时间变化可能是不同清晰度条件下持续语音加工的客观标志。在清晰的语音理解过程中,听者似乎通过增加额外的资源来保持高效的语义处理,而嘈杂的语音导致处理效率降低。当应用于增强语音时,这些N400模式揭示了SE对语义处理的直接好处和支持持续听力的潜在局限性。这些发现证明了N400可预测性效应在理解持续倾听需求和评估SE有效性方面的潜在效用。
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来源期刊
Ear and Hearing
Ear and Hearing 医学-耳鼻喉科学
CiteScore
5.90
自引率
10.80%
发文量
207
审稿时长
6-12 weeks
期刊介绍: From the basic science of hearing and balance disorders to auditory electrophysiology to amplification and the psychological factors of hearing loss, Ear and Hearing covers all aspects of auditory and vestibular disorders. This multidisciplinary journal consolidates the various factors that contribute to identification, remediation, and audiologic and vestibular rehabilitation. It is the one journal that serves the diverse interest of all members of this professional community -- otologists, audiologists, educators, and to those involved in the design, manufacture, and distribution of amplification systems. The original articles published in the journal focus on assessment, diagnosis, and management of auditory and vestibular disorders.
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