Choi Hyo Jung, Kyong Jeong-Sug, Won Jong Ho, Shim Hyun Joon
Department of Otorhinolaryngology-Head and Neck Surgery, Nowon Eulji Medical Center, Eulji University School of Medicine, Seoul, Republic of Korea.
Eulji Tinnitus and Hearing Research Institute, Nowon Eulji Medical Center, Seoul, Republic of Korea.
Front Neurosci. 2025 May 2;19:1493641. doi: 10.3389/fnins.2025.1493641. eCollection 2025.
In our previous study, early-blind individuals have better speech recognition than sighted individuals, even when the spectral cue was degraded using noise-vocoders. Therefore, this study investigated the impact of temporal envelope degradation and temporal fine structure (TFS) degradation on vocoded speech recognition and cortical auditory response in early blind individuals compared to sighted individuals. The study included 20 early-blind subjects (31.20 ± 42.5 years, M: F = 11:9), and 20 age- and -sex-matched sighted subjects. Monosyllabic words were processed using the Hilbert transform to separate the envelope and TFS, generating vocoders that included only one of these components. The amplitude modulation (AM) vocoder, which contained only the envelope component, had the low-pass filter's cutoff frequency for AM extraction set at 16, 50, and 500 Hz to control the amount of AM cue. The frequency modulation (FM) vocoders, which contained only the TFS component, were adjusted to include FM cues at 50%, 75%, and 100% by modulating the noise level. A two-way repeated measures ANOVA revealed that early-blind subjects outperforming sighted subjects across almost all AM or FM-vocoded conditions ( < 0.01). Speech recognition in early-blind subjects declined more with increasing TFS degradation, as evidenced by a significant interaction between group and the degree of TFS degradation ( = 0.016). We also analyzed neural responses based on the semantic oddball paradigm using the N2 and P3b components, which occur 200-300 ms and 250-800 ms after stimulus onset, respectively. Significant correlations were observed between N2 and P3b amplitude/latency and behavioral accuracy ( < 0.05). This suggests that early-blind subjects may develop enhanced neural processing strategies for temporal cues. In particular, preserving TFS cues is considered important for the auditory rehabilitation of individuals with visual or auditory impairments.
在我们之前的研究中，即使使用噪声声码器使频谱线索退化，早期失明个体的语音识别能力仍优于视力正常个体。因此，本研究调查了与视力正常个体相比，时间包络退化和时间精细结构（TFS）退化对早期失明个体的声码语音识别和皮质听觉反应的影响。该研究纳入了20名早期失明受试者（年龄31.20±42.5岁，男性∶女性 = 11∶9）以及20名年龄和性别匹配的视力正常受试者。使用希尔伯特变换对单音节词进行处理，以分离包络和TFS，生成仅包含其中一个成分的声码器。仅包含包络成分的调幅（AM）声码器，将用于提取AM的低通滤波器截止频率设置为16、50和500 Hz，以控制AM线索的量。仅包含TFS成分的调频（FM）声码器，通过调制噪声水平，调整为包含50%、75%和100%的FM线索。双向重复测量方差分析显示，在几乎所有AM或FM声码条件下，早期失明受试者的表现均优于视力正常受试者（<0.01）。早期失明受试者的语音识别能力随TFS退化程度的增加而下降得更多，这一点通过组与TFS退化程度之间的显著交互作用得到证明（=0.016）。我们还基于语义Oddball范式，使用分别在刺激开始后200 - 300毫秒和250 - 800毫秒出现的N2和P3b成分，分析了神经反应情况。观察到N2和P3b的振幅/潜伏期与行为准确性之间存在显著相关性（<0.05）。这表明早期失明受试者可能会为时间线索发展出增强的神经处理策略。特别是，保留TFS线索被认为对于视觉或听觉障碍个体的听觉康复很重要。
