Waisman Center, University of Wisconsin-Madison, 1500 Highland Avenue, Madison, Wisconsin 53705, USA.
Department of Hearing and Speech Sciences, University of Maryland, College Park, Maryland 20742, USA.
J Acoust Soc Am. 2019 Aug;146(2):1448. doi: 10.1121/1.5123464.
Bilateral cochlear implantation has provided access to some of the benefits of binaural hearing enjoyed by normal-hearing (NH) listeners. However, a gap in performance still exists between the two populations. Single-channel stimulation studies have shown that interaural place-of-stimulation mismatch (IPM) due to differences in implantation depth leads to decreased binaural fusion and lateralization of interaural time and level differences (ITDs and ILDs, respectively). While single-channel studies are informative, multi-channel stimulation is needed for good speech understanding with cochlear implants (CIs). Some multi-channel studies have shown that channel interaction due to current spread can affect ITD sensitivity. In this work, we studied the effect of IPM and channel spacing, along with their potential interaction, on binaural fusion and ITD/ILD lateralization. Experiments were conducted in adult NH listeners and CI listeners with a history of acoustic hearing. Results showed that IPM reduced the range of lateralization for ITDs but not ILDs. CI listeners were more likely to report a fused percept in the presence of IPM with multi-channel stimulation than NH listeners. However, no effect of channel spacing was found. These results suggest that IPM should be accounted for in clinical mapping practices in order to maximize bilateral CI benefits.
双侧人工耳蜗植入为一些正常听力（NH）听众所享有的双耳听力益处提供了途径。然而，这两个群体之间的表现仍存在差距。单通道刺激研究表明，由于植入深度的差异导致的刺激间位置不匹配（IPM）会导致双耳融合和刺激间时间和强度差（ITD 和 ILD，分别）的侧化降低。虽然单通道研究提供了信息，但多通道刺激对于人工耳蜗植入（CI）的良好言语理解是必要的。一些多通道研究表明，由于电流扩散引起的通道相互作用会影响 ITD 敏感性。在这项工作中，我们研究了 IPM 和通道间隔及其潜在相互作用对双耳融合和 ITD/ILD 侧化的影响。实验在具有听觉史的成年 NH 听众和 CI 听众中进行。结果表明，IPM 减小了 ITD 的侧化范围，但不影响 ILD。与 NH 听众相比，多通道刺激存在 IPM 时，CI 听众更有可能报告融合感知。然而，未发现通道间隔的影响。这些结果表明，为了最大限度地发挥双侧 CI 的益处，应在临床映射实践中考虑 IPM。
