Department of Communication Sciences and Disorders, East Carolina University, Greenville, North Carolina, United States of America.
Department of Engineering, East Carolina University, Greenville, North Carolina, United States of America.
PLoS One. 2020 Jul 20;15(7):e0236179. doi: 10.1371/journal.pone.0236179. eCollection 2020.
Previous cochlear implant (CI) research has shown that at a pulse train with a long pulse phase duration (PPD) requires less current but greater charge to obtain the same loudness as a pulse train with a short PPD. This might result in different excitation patterns between long and short PPDs. At equal loudness, long PPDs might produce greater masking due to greater charge. However, because they require less current, long PPDs may produce a smaller spatial spread of excitation (SOE) compared to short PPDs by evoking a greater neural firing probability within the relatively small current field. To investigate the effects of PPD on excitation patterns, overall masking and SOE were compared for equally loud stimuli with short or long PPD in 10 adult CI ears. Forward masking patterns were measured at relatively soft, medium, and loud presentation levels. Threshold shifts were calculated in terms of percent dynamic range (DR) of the probe. The area under the curve (AUC) of the masking functions was significantly larger for the long PPD than for the short PPD masker. The difference in AUC was proportional to the difference in charge between the short and long PPD maskers. To estimate SOE, the masking patterns were first normalized to the peak masking, and then AUC was calculated. SOE was significantly larger for the short PPD than for the long PPD masker. Thus, at equal loudness, long PPDs produced greater overall masking (possibly due to greater charge) but less SOE (possibly due to less current spread) than did short PPDs. The effect of the interaction between masking and SOE by long PPD stimulation remains to be tested.
先前的人工耳蜗（CI）研究表明，在长脉冲相位持续时间（PPD）的脉冲串中，需要较少的电流但更多的电荷才能获得与短 PPD 脉冲串相同的响度。这可能导致长 PPD 和短 PPD 之间的刺激模式不同。在相同的响度下，由于更大的电荷量，长 PPD 可能会产生更大的掩蔽。然而，由于它们需要较少的电流，长 PPD 可能会通过在相对较小的电流场中引起更大的神经放电概率，产生比短 PPD 更小的激发空间分布（SOE）。为了研究 PPD 对激发模式的影响，在 10 个成人 CI 耳朵中，比较了具有短或长 PPD 的相等响度刺激的整体掩蔽和 SOE。在相对软、中、大声呈现水平下测量了前向掩蔽模式。阈值偏移以探针的动态范围（DR）的百分比计算。长 PPD 的掩蔽函数的曲线下面积（AUC）显著大于短 PPD 的掩蔽函数。AUC 的差异与短和长 PPD 掩蔽器之间的电荷量差异成正比。为了估计 SOE，首先将掩蔽模式归一化为峰值掩蔽，然后计算 AUC。短 PPD 的 SOE 显著大于长 PPD 的掩蔽器。因此，在相等的响度下，长 PPD 产生的整体掩蔽（可能是由于更大的电荷量）比短 PPD 小，但 SOE 较小（可能是由于电流分布较小）。长 PPD 刺激对掩蔽和 SOE 之间相互作用的影响仍有待测试。
