单侧重度听力损失中言语相关皮层活动的半球偏侧化改变：一项fMRI研究

文献信息

中文摘要

背景： 单侧重度听力损失在初始治疗后通常采取保守管理，因为对侧耳的听力得以保留。然而，患者经常出现言语感知困难，尤其是在噪声环境中，而传统的听力学评估未能完全反映这些困难。由于中枢听觉通路主要投射至对侧半球，且言语处理通常呈左侧化，来自右耳的输入可能更直接地到达左半球言语区。这种解剖和功能上的不对称性提示，听力损失侧别可能对言语相关皮层处理产生不同影响。
目的： 本研究旨在探讨重度语后单侧听力损失患者在言语感知过程中的皮层活动，并检验耳别特异性输入对半球偏侧化的影响。
方法： 对重度单侧听力损失个体（右侧和左侧）及正常听力对照者在言语感知任务中进行了功能磁共振成像（fMRI）。听觉刺激（单音节词和纯音）以双耳方式呈现。对初级听觉皮层（颞横回，TTG）和颞上回（STG）进行了感兴趣区分析。比较了各组之间的平均激活和偏侧化指数。
结果： 在初级听觉皮层中未观察到显著的组间差异。相反，与对照组相比，单侧听力损失患者的STG活动显著降低，尤其是在右侧听力损失组中。STG活动的半球偏侧化发生改变，在左侧听力损失组中观察到左侧优势增加。
结论： 单侧听力损失影响的是高级言语相关皮层处理，而非初级听觉反应。观察到的STG活动和偏侧化变化提示，耳别特异性听觉输入影响皮层组织。这些发现与右耳优势的概念一致，并为单侧听力损失中的言语感知困难提供了神经生理学见解。

英文摘要

BACKGROUND: Severe unilateral hearing loss is often managed conservatively after initial treatment because hearing in the contralateral ear is preserved. However, patients frequently experience difficulties in speech perception, particularly in noisy environments, that are not fully captured by conventional audiological assessments. Because central auditory pathways project predominantly to the contralateral hemisphere and speech processing is typically left-lateralized, input from the right ear may reach the left-hemispheric speech areas more directly. This anatomical and functional asymmetry suggests that the side of hearing loss could differentially affect speech-related cortical processing.
OBJECTIVE: This study aimed to investigate cortical activity during speech perception in severe postlingual unilateral hearing loss and examine the effects of ear-specific input on hemispheric lateralization.
METHODS: Functional magnetic resonance imaging (fMRI) was performed in individuals with severe unilateral hearing loss (right- and left-sided) and in normal-hearing controls during a speech perception task. Auditory stimuli (monosyllables and pure tones) were presented binaurally. Region-of-interest analyses were conducted for the primary auditory cortex (transverse temporal gyrus, TTG) and the superior temporal gyrus (STG). The mean activation and laterality indices were compared between the groups.
RESULTS: No significant intergroup differences were observed in the primary auditory cortex. In contrast, STG activity was significantly reduced in patients with unilateral hearing loss compared to controls, particularly in the right-sided hearing loss group. The hemispherical lateralization of STG activity was altered, with increased leftward dominance observed in the left-sided hearing loss group.
CONCLUSION: Unilateral hearing loss affects higher-order speech-related cortical processing rather than primary auditory responses. The observed changes in STG activity and lateralization suggest that ear-specific auditory input influences the cortical organization. These findings are consistent with the concept of a right-ear advantage and provide neurophysiological insights into speech perception difficulties in unilateral hearing loss.