de Balthasar C, Boëx C, Cosendai G, Valentini G, Sigrist A, Pelizzone M
Department of Otolaryngology-Head and Neck Surgery, Cantonal University Hospital, 1211 Geneva 14, Switzerland.
Hear Res. 2003 Aug;182(1-2):77-87. doi: 10.1016/s0378-5955(03)00174-6.
Channel interactions were assessed using high-rate stimulation in cochlear implant subjects using the Ineraid electrode array. Stimulation currents were applied on one intracochlear electrode and their effects on psychophysical detection thresholds on an adjacent electrode were measured. Stimuli were trains of brief, biphasic, 50-micros/phase pulses presented at a rate of 2000 pulses per second per channel. In experiment I, we studied how the detection of a probe signal was influenced by a sub-threshold perturbation signal presented either simultaneously or non-simultaneously (with no overlap) on an adjacent electrode. Results showed that simultaneous activation led to strong channel interactions, producing threshold changes consistent with instantaneous electric field summation. Non-simultaneous activation revealed much weaker interactions, producing threshold changes of opposite sign. In experiment II, we studied how the temporal delay between perturbation and probe pulses, as well as how the level of the perturbation signal influenced non-simultaneous channel interactions. First, threshold changes when reversing the polarity of the perturbation did progressively vanish when increasing the delay between pulses. This suggested that non-overlapping stimulation of adjacent electrodes produced channel interactions that were in part due to residual polarization of the nerve membrane. Second, increasing the perturbation to supra-threshold levels produced threshold elevations that were independent of the interpulse interval. This suggested channel interactions due to neural masking. These results provide insights into the different concurrently active mechanisms of channel interactions in cochlear implant systems using this type of stimuli.
使用Ineraid电极阵列，通过对人工耳蜗受试者进行高速刺激来评估通道间的相互作用。刺激电流施加于一个耳蜗内电极，并测量其对相邻电极上心理物理检测阈值的影响。刺激为每通道每秒2000个脉冲的短双相50微秒/相脉冲序列。在实验I中，我们研究了在相邻电极上同时或非同时（无重叠）呈现的阈下微扰信号如何影响探测信号的检测。结果表明，同时激活会导致强烈的通道间相互作用，产生与瞬时电场总和一致的阈值变化。非同时激活显示出弱得多的相互作用，产生相反符号的阈值变化。在实验II中，我们研究了微扰脉冲与探测脉冲之间的时间延迟，以及微扰信号的强度如何影响非同时通道间的相互作用。首先，当增加脉冲间延迟时，微扰极性反转时的阈值变化逐渐消失。这表明相邻电极的非重叠刺激产生的通道间相互作用部分归因于神经膜的残余极化。其次，将微扰增加到阈上水平会产生与脉冲间隔无关的阈值升高。这表明存在由于神经掩蔽导致的通道间相互作用。这些结果为使用此类刺激的人工耳蜗系统中通道间相互作用的不同同时激活机制提供了见解。
