STADIUS Center for Dynamical Systems, Signal Processing and Data Analytics, Department of Electrical Engineering (ESAT), KU Leuven, Kasteelpark Arenberg 10 bus 2440, 3001 LEUVEN, Belgium. Experimental ORL, Department of Neurosciences, KU Leuven, Herestraat 49 bus 721, 3000 LEUVEN, Belgium.
J Neural Eng. 2018 Feb;15(1):016006. doi: 10.1088/1741-2552/aa87ce.
Electrically evoked auditory steady-state responses (EASSRs) are potentially useful for objective cochlear implant (CI) fitting and follow-up of the auditory maturation in infants and children with a CI. EASSRs are recorded in the electro-encephalogram (EEG) in response to electrical stimulation with continuous pulse trains, and are distorted by significant CI artifacts related to this electrical stimulation. The aim of this study is to evaluate a CI artifacts attenuation method based on independent component analysis (ICA) for three EASSR datasets.
ICA has often been used to remove CI artifacts from the EEG to record transient auditory responses, such as cortical evoked auditory potentials. Independent components (ICs) corresponding to CI artifacts are then often manually identified. In this study, an ICA based CI artifacts attenuation method was developed and evaluated for EASSR measurements with varying CI artifacts and EASSR characteristics. Artifactual ICs were automatically identified based on their spectrum.
For 40 Hz amplitude modulation (AM) stimulation at comfort level, in high SNR recordings, ICA succeeded in removing CI artifacts from all recording channels, without distorting the EASSR. For lower SNR recordings, with 40 Hz AM stimulation at lower levels, or 90 Hz AM stimulation, ICA either distorted the EASSR or could not remove all CI artifacts in most subjects, except for two of the seven subjects tested with low level 40 Hz AM stimulation. Noise levels were reduced after ICA was applied, and up to 29 ICs were rejected, suggesting poor ICA separation quality.
We hypothesize that ICA is capable of separating CI artifacts and EASSR in case the contralateral hemisphere is EASSR dominated. For small EASSRs or large CI artifact amplitudes, ICA separation quality is insufficient to ensure complete CI artifacts attenuation without EASSR distortion.
电诱发听觉稳态响应（EASSRs）可用于客观的人工耳蜗（CI）适配以及植入 CI 的婴儿和儿童听觉成熟的随访。EASSRs 通过对连续脉冲序列的电刺激在脑电图（EEG）中记录，并受到与这种电刺激相关的显著 CI 伪影的扭曲。本研究旨在评估一种基于独立成分分析（ICA）的 CI 伪影衰减方法，用于三个 EASSR 数据集。
ICA 常用于从 EEG 中去除 CI 伪影以记录瞬态听觉反应，如皮质诱发电位。然后，通常手动识别与 CI 伪影相对应的独立成分（ICs）。在这项研究中，开发了一种基于 ICA 的 CI 伪影衰减方法，并针对具有不同 CI 伪影和 EASSR 特征的 EASSR 测量进行了评估。基于其频谱自动识别伪迹 ICs。
在舒适水平的 40 Hz 调幅（AM）刺激下，在高 SNR 记录中，ICA 成功地从所有记录通道去除了 CI 伪影，而不会扭曲 EASSR。对于 SNR 较低的记录，40 Hz AM 刺激水平较低或 90 Hz AM 刺激，ICA 要么扭曲了 EASSR，要么无法在大多数受试者中去除所有 CI 伪影，只有 7 名接受低水平 40 Hz AM 刺激的受试者中的两名除外。ICA 应用后噪声水平降低，多达 29 个 ICs 被拒绝，表明 ICA 分离质量差。
我们假设，在对侧半球为 EASSR 主导的情况下，ICA 能够分离 CI 伪影和 EASSR。对于较小的 EASSR 或较大的 CI 伪影幅度，ICA 分离质量不足以确保在不扭曲 EASSR 的情况下完全去除 CI 伪影。
