École d'orthophonie et d'audiologie, Faculté de médecine, Université de Montréal, Montréal, Québec, Canada.
Centre de recherche de l'Institut universitaire de gériatrie de Montréal, Montréal, Québec, Canada.
PLoS One. 2021 May 7;16(5):e0251287. doi: 10.1371/journal.pone.0251287. eCollection 2021.
Some evidence suggests that young adults exhibit a selective laterality of auditory brainstem response (ABR) elicited with speech stimuli. Little is known about such an auditory laterality in older adults.
The aim of this study was to investigate possible asymmetric auditory brainstem processing between right and left ear presentation in older adults.
Sixty-two older adults presenting with normal hearing thresholds according to their age and who were native speakers of Quebec French participated in this study. ABR was recorded using click and a 40-ms /da/ syllable. ABR was elicited through monaural right and monaural left stimulation. Latency and amplitude for click-and speech-ABR components were compared between right and left ear presentations. In addition, for the /da/ syllable, a fast Fourier transform analysis of the sustained frequency-following response (FFR) of the vowel was performed along with stimulus-to-response and right-left ear correlation analyses.
No significant differences between right and left ear presentation were found for amplitudes and latencies of the click-ABR components. Significantly shorter latencies for right ear presentation as compared to left ear presentation were observed for onset and offset transient components (V, A and O), sustained components (D and E), and voiced transition components (C) of the speech-ABR. In addition, the spectral amplitude of the fundamental frequency (F0) was significantly larger for the left ear presentation than the right ear presentation.
Results of this study show that older adults with normal hearing exhibit symmetric encoding for click stimuli at the brainstem level between the right and left ear presentation. However, they present with brainstem asymmetries for the encoding of selective stimulus components of the speech-ABR between the right and left ear presentation. The right ear presentation of a /da/ syllable elicited reduced neural timing for both transient and sustained components compared to the left ear. Conversely, a stronger left ear F0 encoding was observed. These findings suggest that at a preattentive, sensory stage of auditory processing, older adults lateralize speech stimuli similarly to young adults.
有证据表明，年轻人在使用言语刺激诱发听觉脑干反应（ABR）时表现出选择性的侧化。对于老年人是否存在这种听觉侧化现象知之甚少。
本研究旨在探讨老年人在右耳和左耳呈现时，右耳和左耳听觉脑干处理是否存在不对称性。
62 名听力正常的老年人参与了本研究，他们的听力阈值符合其年龄，并且都是魁北克法语的母语者。使用短声和 40ms /da/ 音节记录 ABR。通过单耳右耳和单耳左耳刺激诱发 ABR。比较右耳和左耳呈现时短声和言语-ABR 成分的潜伏期和振幅。此外，对于 /da/ 音节，还进行了元音的持续频率跟随反应（FFR）的快速傅里叶变换分析，并进行了刺激-反应和右-左耳相关性分析。
右耳和左耳呈现时，短声-ABR 成分的振幅和潜伏期无显著差异。与左耳呈现相比，右耳呈现时起始和结束瞬态成分（V、A 和 O）、持续成分（D 和 E）和浊音过渡成分（C）的潜伏期明显缩短。此外，左耳呈现时基频（F0）的频谱幅度明显大于右耳呈现时。
本研究结果表明，听力正常的老年人在右耳和左耳呈现时，脑干水平对短声刺激的编码具有对称性。然而，在右耳和左耳呈现时，言语-ABR 的选择性刺激成分的编码存在脑干不对称性。与左耳相比，右耳呈现的 /da/ 音节诱发的瞬态和持续成分的神经时程更短。相反，观察到更强的左耳 F0 编码。这些发现表明，在听觉处理的非注意、感觉阶段，老年人对言语刺激的侧化与年轻人相似。
