Saoji Aniket A, Litvak Leonid M, Hughes Michelle L
Auditory Research and Development, Advanced Bionics Corporation, Sylmar, CA, USA.
Ear Hear. 2009 Oct;30(5):559-67. doi: 10.1097/AUD.0b013e3181ab2b6f.
Both simultaneous (SI) and sequential stimulation of intracochlear electrodes can be used to generate pitches that are intermediate to the physical electrodes (PEs). The goal of this study was to compare the spread of neural excitation for SI and sequential dual-electrode stimulation with the spread of neural excitation for the intermediate electrode using electrically evoked compound action potentials.
Seven Advanced Bionics cochlear implant users with either CII or HiRes 90k implant and HiFocus 1 or HiFocus 1j electrode array participated in this study. A masker-probe subtraction method was used to derive neural excitation patterns for SI nonadjacent dual-electrode stimulation, apical and basal-first sequential nonadjacent dual-electrode stimulation, and the intermediate PE. For apical-first sequential (SEa) stimulation, the masker pulse on the apical electrode immediately preceded the masker pulse on the basal electrode, and vice versa for basal-first sequential stimulation (SEb). The electrodes used for dual-electrode stimulation were separated by an intermediate PE, which represents a spatial distance of approximately 2 mm. Current levels necessary to achieve comfortable loudness were determined for each masker and probe stimulus. During the evoked compound action potential measurements, the masker was fixed in location, whereas the probe was varied across a subset of electrodes in the array. Neural responses were calculated by subtracting the response to the probe from the masked response.
Neural excitation patterns were normalized to their peak and analyzed in terms of their area and center of gravity. The area and center of gravity for SI nonadjacent dual-electrode stimulation were similar to those of the intermediate PE. In contrast, the area for the two modes of sequential nonadjacent dual-electrode (SEa and SEb) stimulation differed significantly from the intermediate PE. The center of gravity for SEa stimulation also differed significantly from the intermediate PE, whereas there was no significant difference in the center of gravity between SEb stimulation and the intermediate PE.
Peripheral neural activation patterns suggest a similar spread of excitation for SI dual-electrode stimulation and the intermediate PE. The spread of excitation associated with sequential dual-electrode stimulation is generally different from the intermediate PE, and it varies depending on the order of the sequential pulses.
耳蜗内电极的同步刺激（SI）和顺序刺激均可用于产生介于物理电极（PE）之间的音调。本研究的目的是使用电诱发复合动作电位，比较SI和顺序双电极刺激的神经兴奋传播与中间电极的神经兴奋传播。
七名使用CII或HiRes 90k植入物以及HiFocus 1或HiFocus 1j电极阵列的Advanced Bionics人工耳蜗使用者参与了本研究。采用掩蔽-探测减法来推导SI非相邻双电极刺激、顶端和基底优先顺序非相邻双电极刺激以及中间PE的神经兴奋模式。对于顶端优先顺序（SEa）刺激，顶端电极上的掩蔽脉冲紧跟在基底电极上的掩蔽脉冲之前，而对于基底优先顺序刺激（SEb）则相反。用于双电极刺激的电极由一个中间PE隔开，这代表了大约2毫米的空间距离。确定了每个掩蔽和探测刺激达到舒适响度所需的电流水平。在诱发复合动作电位测量期间，掩蔽电极位置固定，而探测电极在阵列中的一部分电极上变化。通过从掩蔽反应中减去对探测电极的反应来计算神经反应。
神经兴奋模式以其峰值进行归一化，并根据其面积和重心进行分析。SI非相邻双电极刺激的面积和重心与中间PE相似。相比之下，两种顺序非相邻双电极（SEa和SEb）刺激模式的面积与中间PE有显著差异。SEa刺激的重心也与中间PE有显著差异，而SEb刺激与中间PE的重心之间没有显著差异。
外周神经激活模式表明SI双电极刺激和中间PE的兴奋传播相似。与顺序双电极刺激相关的兴奋传播通常与中间PE不同，并且它取决于顺序脉冲的顺序。
