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Temporal Modulations of Listening Fatigue on Predictive Processing during Speech Comprehension: An ERP N400 Study
Poster Session C, Friday, October 25, 4:30 - 6:00 pm, Great Hall 3 and 4
Cheng-Hung Hsin1, Chia-Ying Lee2, Yu Tsao1; 1Biomedical Acoustic Signal Processing Lab, Research Center for Information Technology Innovation, Academia Sinica, 2Brain and Language Laboratory, Institute of Linguistics, Academia Sinica
Listeners utilize linguistic context to predict upcoming speech information. However, the influence of listening fatigue resulting from sustained attentive listening on lexical predictions remains unclear, particularly under varying speech clarity conditions. This study investigated the temporal modulations of listening fatigue on the predictability effect on the N400 under clear and noisy conditions, examining changes in amplitude, latency, and topographic distributions over time. A between-subjects design was employed, with two age- and hearing-matched groups (N=70) comprehending clear or noise-masked spoken sentences ending in high- or low-predictability words for approximately 30 minutes during electroencephalogram (EEG) recordings. The stimuli included 128 sentences, with a quarter of trials requiring participants to respond to comprehension questions. The data were divided into two blocks to investigate the effects of listening fatigue over time. Cluster-based permutation tests revealed that in the clear condition, Block 1 exhibited a significant predictability effect on the N400 from 300-700 ms, whereas in Block 2, the effect was present from 300-900 ms with a more anterior spread scalp distribution without amplitude reductions or onset delays. In the noisy condition, Block 1 showed a significant but discontinuous effect from 400-500 ms and 700-900 ms, while in Block 2, the effect was delayed but consistent from 500-900 ms, with a posterior distribution relative to Block 1. Difference wave analysis revealed no significant differences in the N400 effects between clarity conditions in Block 1. However, in Block 2, the noisy condition exhibited a significantly reduced, delayed, and posteriorly distributed effect on the N400 compared to the clear condition. The findings demonstrate that listening fatigue differentially modulates semantic processing under clear and noisy conditions. In clear speech, listeners maintain processing efficiency by recruiting frontal resources over time. In contrast, noisy speech compromises processing efficiency and integrity without evident frontal recruitment. The results suggest that listening fatigue can develop in the absence of sensory distress, and reserved frontal resources can be recruited to maintain efficient semantic processing. However, noisy speech rapidly depletes attentional resources, leaving few to support efficient semantic processing over time. Despite listening fatigue, noise adaptation seems to occur concurrently. Temporal modulations of the predictability effect on the N400 provide valuable insights into the relationship between listening fatigue and resource availability that ultimately determines semantic processing efficiency.
Topic Areas: Speech Perception, Meaning: Lexical Semantics