Center for Music in the Brain, dept. of Clinical Medicine, Aarhus University & The Royal Academy of Music Aarhus/Aalborg, Denmark.
Center for Music in the Brain, dept. of Clinical Medicine, Aarhus University & The Royal Academy of Music Aarhus/Aalborg, Denmark.
Hear Res. 2024 Oct;452:109105. doi: 10.1016/j.heares.2024.109105. Epub 2024 Aug 14.
Cochlear implant (CI) users experience diminished music enjoyment due to the technical limitations of the CI. Nonetheless, behavioral studies have reported that rhythmic features are well-transmitted through the CI. Still, the gradual improvement of rhythm perception after the CI switch-on has not yet been determined using neurophysiological measures. To fill this gap, we here reanalyzed the electroencephalographic responses of participants from two previous mismatch negativity studies. These studies included eight recently implanted CI users measured twice, within the first six weeks after CI switch-on and approximately three months later; thirteen experienced CI users with a median experience of 7 years; and fourteen normally hearing (NH) controls. All participants listened to a repetitive four-tone pattern (known in music as Alberti bass) for 35 min. Applying frequency tagging, we aimed to estimate the neural activity synchronized to the periodicities of the Alberti bass. We hypothesized that longer experience with the CI would be reflected in stronger frequency-tagged neural responses approaching the responses of NH controls. We found an increase in the frequency-tagged amplitudes after only 3 months of CI use. This increase in neural synchronization may reflect an early adaptation to the CI stimulation. Moreover, the frequency-tagged amplitudes of experienced CI users were significantly greater than those of recently implanted CI users, but still smaller than those of NH controls. The frequency-tagged neural responses did not just reflect spectrotemporal changes in the stimuli (i.e., intensity or spectral content fluctuating over time), but also showed non-linear transformations that seemed to enhance relevant periodicities of the Alberti bass. Our findings provide neurophysiological evidence indicating a gradual adaptation to the CI, which is noticeable already after three months, resulting in close to NH brain processing of spectrotemporal features of musical rhythms after extended CI use.
人工耳蜗（CI）用户由于 CI 的技术限制而体验到音乐享受的减少。尽管如此，行为研究报告称，节奏特征通过 CI 得到很好的传递。然而，CI 开关后节奏感知的逐渐改善尚未通过神经生理测量来确定。为了填补这一空白，我们在这里重新分析了来自两项先前失匹配负波研究的参与者的脑电图反应。这些研究包括八名最近植入 CI 的参与者，在 CI 开关后最初的六周内和大约三个月后进行了两次测量；十三名有经验的 CI 用户，中位数经验为 7 年；以及十四名正常听力（NH）对照组。所有参与者听了 35 分钟重复的四音模式（在音乐中称为 Alberti 低音）。应用频率标记，我们旨在估计与 Alberti 低音周期性同步的神经活动。我们假设，CI 的使用经验越长，频率标记的神经反应就越强，接近 NH 对照组的反应。我们发现，仅在使用 CI 3 个月后，频率标记的幅度就增加了。这种神经同步的增加可能反映了对 CI 刺激的早期适应。此外，经验丰富的 CI 用户的频率标记幅度明显大于最近植入 CI 用户的幅度，但仍小于 NH 对照组的幅度。频率标记的神经反应不仅反映了刺激的谱时变化（即随时间波动的强度或频谱内容），还显示出非线性变换，似乎增强了 Alberti 低音的相关周期性。我们的研究结果提供了神经生理学证据，表明对 CI 的逐渐适应，这在使用 CI 三个月后就可以注意到，这导致在扩展 CI 使用后，对音乐节奏的谱时特征的 NH 大脑处理接近。
