ExpORL, Department Neurosciences, K.U.Leuven, O&N 2, Herestraat 49 bus 721, 3000, Leuven, Belgium.
J Assoc Res Otolaryngol. 2012 Aug;13(4):573-89. doi: 10.1007/s10162-012-0321-8. Epub 2012 May 9.
Electrically evoked auditory steady-state responses (EASSRs) are EEG potentials in response to periodic electrical stimuli presented through a cochlear implant. For low-rate pulse trains in the 40-Hz range, electrophysiological thresholds derived from response amplitude growth functions correlate well with behavioral T levels at these rates. The aims of this study were: (1) to improve the correlation between electrophysiological thresholds and behavioral T levels at 900 pps by using amplitude-modulated (AM) and pulse-width-modulated (PWM) high-rate pulse trains, (2) to develop and evaluate the performance of a new statistical method for response detection which is robust in the presence of stimulus artifacts, and (3) to assess the ability of this statistical method to determine reliable electrophysiological thresholds without any stimulus artifact removal. For six users of a Nucleus cochlear implant and a total of 12 stimulation electrode pairs, EASSRs to symmetric biphasic bipolar pulse trains were recorded with seven scalp electrodes. Responses to six different stimuli were analyzed: two low-rate pulse trains with pulse rates in the 40-Hz range as well as two AM and two PWM high-rate pulse trains with a carrier rate of 900 pps and modulation frequencies in the 40-Hz range. Responses were measured at eight different stimulus intensities for each stimulus and stimulation electrode pair. Artifacts due to the electrical stimulation were removed from the recordings. To determine the presence of a neural response, a new statistical method based on a two-sample Hotelling T (2) test was used. Measurements from different recording electrodes and adjacent stimulus intensities were combined to increase statistical power. The results show that EASSRs to modulated high-rate pulse trains account for some of the temporal effects at 900 pps and result in improved electrophysiological thresholds that correlate very well with behavioral T levels at 900 pps. The proposed statistical method for response detection based on a two-sample Hotelling T (2) test has comparable performance to previously used one-sample tests and does not require stimulus artifacts to be removed from the EEG signal for the determination of reliable electrophysiological thresholds.
电诱发听觉稳态反应 (EASSR) 是对通过人工耳蜗呈现的周期性电刺激的 EEG 电位。对于 40Hz 范围内的低速率脉冲串，从响应幅度增长函数得出的电生理阈值与这些速率下的行为 T 水平很好地相关。本研究的目的是：(1) 通过使用幅度调制 (AM) 和脉冲宽度调制 (PWM) 高速率脉冲串，提高 900pps 时电生理阈值与行为 T 水平之间的相关性；(2) 开发并评估一种新的统计方法，该方法在存在刺激伪影的情况下具有稳健性，用于响应检测；(3) 评估该统计方法在无需去除任何刺激伪影的情况下确定可靠电生理阈值的能力。对于 Nucleus 人工耳蜗的六位使用者和总共 12 个刺激电极对，使用七个头皮电极记录对称双相双极脉冲串的 EASSR。分析了六种不同刺激的反应：两个脉冲率在 40Hz 范围内的低速率脉冲串，以及两个 AM 和两个 PWM 高速率脉冲串，载波率为 900pps，调制频率在 40Hz 范围内。对于每个刺激和刺激电极对，在八个不同的刺激强度下测量响应。从记录中去除由于电刺激而产生的伪影。为了确定神经反应的存在，使用了一种基于两样本 Hotelling T(2)检验的新统计方法。从不同的记录电极和相邻的刺激强度进行测量，以提高统计能力。结果表明，调制的高速率脉冲串的 EASSR 解释了 900pps 时的一些时间效应，并导致电生理阈值得到改善，与 900pps 时的行为 T 水平非常相关。基于两样本 Hotelling T(2)检验的新的响应检测统计方法与之前使用的单样本检验具有相当的性能，并且不需要从 EEG 信号中去除刺激伪影来确定可靠的电生理阈值。
