School of Computer Science and Statistics, ADAPT Centre, Trinity College Dublin, Dublin, Ireland.
Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland.
PLoS One. 2024 Nov 22;19(11):e0308554. doi: 10.1371/journal.pone.0308554. eCollection 2024.
Hearing impairment alters the sound input received by the human auditory system, reducing speech comprehension in noisy multi-talker auditory scenes. Despite such difficulties, neural signals were shown to encode the attended speech envelope more reliably than the envelope of ignored sounds, reflecting the intention of listeners with hearing impairment (HI). This result raises an important question: What speech-processing stage could reflect the difficulty in attentional selection, if not envelope tracking? Here, we use scalp electroencephalography (EEG) to test the hypothesis that the neural encoding of phonological information (i.e., phonetic boundaries and phonological categories) is affected by HI. In a cocktail-party scenario, such phonological difficulty might be reflected in an overrepresentation of phonological information for both attended and ignored speech sounds, with detrimental effects on the ability to effectively focus on the speaker of interest. To investigate this question, we carried out a re-analysis of an existing dataset where EEG signals were recorded as participants with HI, fitted with hearing aids, attended to one speaker (target) while ignoring a competing speaker (masker) and spatialised multi-talker background noise. Multivariate temporal response function (TRF) analyses indicated a stronger phonological information encoding for target than masker speech streams. Follow-up analyses aimed at disentangling the encoding of phonological categories and phonetic boundaries (phoneme onsets) revealed that neural signals encoded the phoneme onsets for both target and masker streams, in contrast with previously published findings with normal hearing (NH) participants and in line with our hypothesis that speech comprehension difficulties emerge due to a robust phonological encoding of both target and masker. Finally, the neural encoding of phoneme-onsets was stronger for the masker speech, pointing to a possible neural basis for the higher distractibility experienced by individuals with HI.
听力障碍改变了人类听觉系统接收到的声音输入，降低了嘈杂多说话者听觉场景中的言语理解能力。尽管存在这些困难，但神经信号被证明比忽略声音的包络更可靠地编码注意力集中的语音包络，反映了听力障碍（HI）听众的意图。这一结果提出了一个重要问题：如果不是包络跟踪，那么哪个语音处理阶段可以反映注意力选择的困难？在这里，我们使用头皮脑电图（EEG）来检验这样一个假设，即语音信息（即语音边界和语音类别）的神经编码受到 HI 的影响。在鸡尾酒会场景中，这种语音困难可能表现为对注意力集中和忽略的语音的语音信息的过度表示，从而对有效关注感兴趣的说话者的能力产生不利影响。为了研究这个问题，我们对一个现有的数据集进行了重新分析，在这个数据集中，当参与者佩戴助听器时，记录了他们的 EEG 信号，他们专注于一个说话者（目标），同时忽略了一个竞争说话者（掩蔽者）和空间化的多说话者背景噪声。多变量时间响应函数（TRF）分析表明，目标语音流的语音信息编码比掩蔽者语音流更强。后续分析旨在分离语音类别和语音边界（音素起始）的编码，结果表明，神经信号对目标和掩蔽者的音素起始都进行了编码，这与我们的假设一致，即由于对目标和掩蔽者的语音都进行了强有力的语音编码，因此出现了言语理解困难。最后，音素起始的神经编码对于掩蔽者的语音更强，这可能为 HI 个体更高的分心提供了一个潜在的神经基础。
