KU Leuven, Department of Neurosciences, ExpORL, Leuven, Belgium.
These authors contributed equally to this work.
Ear Hear. 2020 May/Jun;41(3):591-602. doi: 10.1097/AUD.0000000000000783.
Cochlear implants (CIs) restore functional hearing in persons with a severe hearing impairment. Despite being one of the most successful bionic prosthesis, performance with CI (in particular speech understanding in noise) varies considerably across its users. The ability of the auditory pathway to encode temporal envelope modulations (TEMs) and the effect of degenerative processes associated with hearing loss on TEM encoding is assumed to be one of the reasons underlying the large intersubject differences in CI performance. The objective of the present study was to investigate how TEM encoding of the stimulated neural ensembles of human CI recipients is related to speech perception in noise (SPIN).
We used electroencephalography as a noninvasive electrophysiological measure to assess TEM encoding in the auditory pathway of CI users by means of the 40-Hz electrically evoked auditory steady state response (EASSR). Nine CI users with a wide range of SPIN outcome were included in the present study. TEM encoding was assessed for each stimulation electrode of each subject and new metrics; the CI neural modulation transmission difference (CIMTD) and the CI neural modulation transmission index (CIMTI) were developed to quantify the amount of variability in TEM encoding across the stimulated neural ensembles of the CI electrode array.
EASSR patterns varied across the CI electrode array and subjects. We found a strong correlation (r = 0.89, p = 0.001) between the SPIN outcomes and the variability in EASSR amplitudes across the array as assessed with CIMTD/CIMTI.
The results of the present study show that the 40-Hz EASSR can be used to objectively assess the neural encoding of TEMs in human CI recipients. Overall reduced or largely variable TEM encoding of the neural ensembles across the electrode array, as quantified with the CIMTD/CIMTI, is highly correlated with speech perception in noise outcome with a CI.
人工耳蜗（CI）为重度听力障碍患者恢复了功能性听力。尽管它是最成功的仿生假体之一，但 CI 的性能（特别是噪声中的言语理解）在用户之间差异很大。听觉通路对时间包络调制（TEM）的编码能力以及与听力损失相关的退行性过程对 TEM 编码的影响，被认为是导致 CI 性能个体间差异较大的原因之一。本研究的目的是调查人类 CI 受者刺激神经簇的 TEM 编码与噪声下言语感知（SPIN）之间的关系。
我们使用脑电图作为一种非侵入性的电生理测量方法，通过 40-Hz 电诱发听觉稳态反应（EASSR）来评估 CI 用户听觉通路中的 TEM 编码。本研究纳入了 9 名 SPIN 结果差异较大的 CI 用户。对每个受试者的每个刺激电极进行 TEM 编码评估，并开发了新的指标；CI 神经调制传递差异（CIMTD）和 CI 神经调制传递指数（CIMTI）用于量化 CI 电极阵列刺激神经簇中的 TEM 编码的变异性。
EASSR 模式在 CI 电极阵列和受试者之间存在差异。我们发现，SPIN 结果与 CIMTD/CIMTI 评估的阵列中 EASSR 幅度的变异性之间存在很强的相关性（r = 0.89，p = 0.001）。
本研究结果表明，40-Hz EASSR 可用于客观评估人类 CI 受者的 TEM 神经编码。总体上，CI 电极阵列上神经簇的 TEM 编码减少或变异性大，如 CIMTD/CIMTI 所量化的，与噪声下的言语感知结果高度相关。
