Zhang Fawen, Samy Ravi N, Anderson Jill M, Houston Lisa
Department of Communication Sciences and Disorders, University of Cincinnati, OH 45267-0379, USA.
J Am Acad Audiol. 2009 Jul-Aug;20(7):397-408. doi: 10.3766/jaaa.20.7.2.
It has been theorized that neural recovery is related to temporal coding of speech sounds. The recovery function of cortically generated auditory evoked potentials has not been investigated in cochlear implant (CI) users.
This study characterized the recovery function of the late auditory evoked potential (LAEP) using a masker-probe paradigm in postlingually deafened adult CI users and young normal-hearing (NH) listeners.
A case-control study of the late auditory evoked potentials using electrophysiological technique was performed. The LAEP was evoked by 1 kHz tone bursts presented in pairs, with the first stimuli as the maskers and the second stimuli as the probes. The masker-probe intervals (MPIs) were varied at 0.7, 1, 2, 4, and 8 sec, with an interpair interval of 12 sec.
Nine CI users and nine NH listeners participated in this study.
The normalized amplitude from the probe response relative to the masker response was plotted as a function of the MPI to form a recovery function. The latency shift for the probe response relative to the masker response was calculated.
The recovery function was approximately linear in log scale of the MPI in NH listeners, while it showed somewhat different recovery patterns with a large intersubject variability in CI users. Specifically, although the probe response was approximately 60 percent of the masker response for the MPI of 0.7 sec in both groups, the recovery function of CI users displayed a nonlinear pattern, with a steeper slope than that of NH listeners. The probe response completely recovered at the MPI of 4 sec in NH listeners and at the MPI of 2 sec in CI users. N1 and P2 latencies from probe responses were shorter than those from masker responses in NH listeners, while no latency difference was found between probe responses and masker responses in CI users.
Our interpretation of these findings is that the faster recovery of the LAEP in CI users is related to abnormal adaptation mechanisms and a less prominent role of the components with longer latencies in the LAEP of CI users. Other mechanisms such as the compromised inhibitory regulation in the auditory system and the aging effect in CI users might also play a role. More research needs to be done to determine whether the slope of the LAEP recovery function is correlated with speech-perception performance.
理论认为神经恢复与语音的时间编码有关。尚未对人工耳蜗（CI）使用者皮质产生的听觉诱发电位的恢复功能进行研究。
本研究采用掩蔽-探测范式，对语后聋成年CI使用者和年轻听力正常（NH）听众的晚期听觉诱发电位（LAEP）恢复功能进行了特征描述。
采用电生理技术对晚期听觉诱发电位进行病例对照研究。LAEP由成对呈现的1kHz短音诱发，第一个刺激为掩蔽音，第二个刺激为探测音。掩蔽-探测间隔（MPI）分别为0.7、1、2、4和8秒，对间间隔为12秒。
9名CI使用者和9名NH听众参与了本研究。
将探测反应相对于掩蔽反应的归一化振幅绘制为MPI的函数，以形成恢复函数。计算探测反应相对于掩蔽反应的潜伏期偏移。
在NH听众中，恢复函数在MPI的对数尺度上近似呈线性，而在CI使用者中则表现出 somewhat different恢复模式，个体间差异较大。具体而言，虽然两组中MPI为0.7秒时探测反应约为掩蔽反应的60%，但CI使用者的恢复函数呈非线性模式，斜率比NH听众更陡。在NH听众中，探测反应在MPI为4秒时完全恢复，在CI使用者中，探测反应在MPI为2秒时完全恢复。NH听众中探测反应的N1和P2潜伏期短于掩蔽反应，而CI使用者中探测反应与掩蔽反应之间未发现潜伏期差异。
我们对这些发现的解释是，CI使用者中LAEP的更快恢复与异常的适应机制以及CI使用者LAEP中潜伏期较长的成分作用不突出有关。其他机制，如听觉系统中受损的抑制调节和CI使用者的衰老效应也可能起作用。需要进行更多研究以确定LAEP恢复函数的斜率是否与言语感知性能相关。
