Hey Matthias, Müller-Deile Joachim, Hessel Horst, Killian Matthijs
Department of Otorhinolaryngology, Head and Neck Surgery, Audiology, University Hospital Schleswig-Holstein (UKSH), Campus Kiel, Kiel, Germany.
Audiology Consultant, Kiel, Germany.
Hear Res. 2017 Nov;355:14-22. doi: 10.1016/j.heares.2017.09.001. Epub 2017 Sep 11.
In this study we aim to resolve the contributions of facilitation and refractoriness at very short pulse intervals. Measurements of the refractory properties of the electrically evoked compound action potential (ECAP) of the auditory nerve in cochlear implant (CI) users at inter pulse intervals below 300 μs are influenced by facilitation and recovery effects. ECAPs were recorded using masker pulses with a wide range of current levels relative to the probe pulse levels, for three suprathreshold probe levels and pulse intervals from 13 to 200 μs. Evoked potentials were measured for 21 CI patients by using the masked response extraction artifact cancellation procedure. During analysis of the measurements the stimulation current was not used as absolute value, but in relation to the patient's individual ECAP threshold. This enabled a more general approach to describe facilitation as a probe level independent effect. Maximum facilitation was found for all tested inter pulse intervals at masker levels near patient's individual ECAP threshold, independent from probe level. For short inter pulse intervals an increased NP amplitude was measured for subthreshold masker levels down to 120 CL below patient's individual ECAP threshold in contrast to the recreated state. ECAPs recorded with inter pulse intervals up to 200 μs are influenced by facilitation and recovery. Facilitation effects are most pronounced for masker levels at or below ECAP threshold, while recovery effects increase with higher masker levels above ECAP threshold. The local maximum of the ECAP amplitude for masker levels around ECAP threshold can be explained by the mutual influence of maximum facilitation and minimal refractoriness.
在本研究中，我们旨在解析在非常短的脉冲间隔下易化和不应期的作用。在人工耳蜗（CI）使用者中，当脉冲间隔低于300微秒时，对听神经电诱发复合动作电位（ECAP）不应期特性的测量会受到易化和恢复效应的影响。使用相对于探测脉冲水平具有广泛电流水平的掩蔽脉冲记录ECAP，针对三个阈上探测水平以及13至200微秒的脉冲间隔。通过使用掩蔽响应提取伪迹消除程序，对21名CI患者测量诱发电位。在测量分析过程中，刺激电流并非作为绝对值使用，而是相对于患者个体的ECAP阈值。这使得能够采用更通用的方法将易化描述为与探测水平无关的效应。在所有测试的脉冲间隔下，在接近患者个体ECAP阈值的掩蔽水平处发现了最大易化，且与探测水平无关。与重建状态相比，对于短脉冲间隔，在低于患者个体ECAP阈值达120 CL的阈下掩蔽水平下测量到NP振幅增加。记录的脉冲间隔长达200微秒的ECAP受易化和恢复的影响。易化效应在掩蔽水平等于或低于ECAP阈值时最为明显，而恢复效应随着高于ECAP阈值的更高掩蔽水平而增加。ECAP阈值附近掩蔽水平下ECAP振幅的局部最大值可通过最大易化和最小不应期的相互影响来解释。
