Research and Technology, Advanced Bionics LLC, 28515 Westinghouse Place, Valencia, California, USA.
Ear Hear. 2018 Jan/Feb;39(1):124-130. doi: 10.1097/AUD.0000000000000471.
Monopolar stimulation of the most apical electrode produces the lowest pitch sensation in cochlear implants clinically. A phantom electrode that uses out-of-phase electrical stimulation between the most apical and the neighboring basal electrode can produce a lower pitch sensation than that associated with the most apical electrode. However, because of the absence of contacts beyond the apical tip of the array, the ability to assess the spread of electrical excitation associated with phantom stimulation is limited in the typical cochlear implant subject with no residual hearing. In the present study, the spread of electrical excitation associated with monopolar and phantom stimulation of the most apical electrode was assessed using electrical masking of acoustic thresholds in cochlear implant subjects with residual, low-frequency, acoustic hearing.
Eight subjects with an Advanced Bionics cochlear implant and residual hearing in the implanted ear participated in this study (nine ears in total). Unmasked and masked thresholds for acoustic pure tones were measured at 125, 250, 500, 750, 1000, and 2000 Hz in the presence of monopolar and phantom electrode stimulation presented at the apical-most end of the array. The current compensation for phantom electrode stimulation was fixed at 50%. The two electrical maskers were loudness balanced. Differences between the unmasked and masked acoustic thresholds can be attributed to (1) the electrical stimulus-induced interference in the transduction/conduction of the acoustic signal through cochlear periphery and the auditory nerve and/or (2) masking at the level of the central auditory system.
The results show a significant elevation in pure-tone thresholds in the presence of the monopolar and phantom electrical maskers. The unmasked thresholds were subtracted from the masked thresholds to derive masking patterns as a function of the acoustic probe frequency. The masking patterns show that phantom stimulation was able to produce more masking than that associated with the monopolar stimulation of the most apical electrode.
These results suggest that for some cochlear implant subjects, phantom electrode stimulation can shift the neural stimulation pattern more apically in the cochlea, which is consistent with reports that phantom electrode stimulation produces lower pitch sensations than those associated with monopolar stimulation of the most apical electrode alone.
在临床上，对最顶端电极进行单极刺激会产生最低音调感。使用最顶端电极和相邻基底电极之间异相电刺激的幻影电极可以产生比与最顶端电极相关的更低音调感。然而，由于阵列的顶端之外没有触点，因此在没有残余听力的典型耳蜗植入物受试者中，评估与幻影刺激相关的电激发传播的能力是有限的。在本研究中，使用残余低频听觉的耳蜗植入物受试者的声学阈值电掩蔽评估了与最顶端电极的单极和幻影刺激相关的电激发传播。
8 名受试者（9 只耳朵）参加了这项研究，他们都在植入耳朵中具有残余低频听觉。在阵列最顶端电极处呈现单极和幻影电极刺激的情况下，测量了 125、250、500、750、1000 和 2000Hz 声学纯音的未掩蔽和掩蔽阈值。幻影电极刺激的电流补偿固定在 50%。两个电掩蔽器的响度平衡。未掩蔽和掩蔽声学阈值之间的差异可归因于（1）电刺激引起的对耳蜗外围和听神经的声信号的转导/传导的干扰和/或（2）中枢听觉系统的掩蔽。
结果表明，在存在单极和幻影电掩蔽器的情况下，纯音阈值显著升高。从掩蔽阈值中减去未掩蔽阈值，以获得作为声学探针频率函数的掩蔽模式。掩蔽模式表明，幻影刺激能够产生比与最顶端电极的单极刺激相关的更多掩蔽。
这些结果表明，对于某些耳蜗植入物受试者，幻影电极刺激可以使耳蜗中的神经刺激模式更向顶部移动，这与幻影电极刺激产生比单独与最顶端电极的单极刺激相关的更低音调感的报道一致。
