Importance of ipsilateral residual hearing for spatial hearing by bimodal cochlear implant users.

Bimodal cochlear implant (CI) listeners have difficulty utilizing spatial cues to segregate competing speech, possibly due to tonotopic mismatch between the acoustic input frequency and electrode place of stimulation. The present study investigated the effects of tonotopic mismatch in the context of residual acoustic hearing in the non-CI ear or residual hearing in both ears. Speech recognition thresholds (SRTs) were measured with two co-located or spatially separated speech maskers in normal-hearing adults listening to acoustic simulations of CIs; low frequency acoustic information was available in the non-CI ear (bimodal listening) or in both ears. Bimodal SRTs were significantly better with tonotopically matched than mismatched electric hearing for both co-located and spatially separated speech maskers. When there was no tonotopic mismatch, residual acoustic hearing in both ears provided a significant benefit when maskers were spatially separated, but not when co-located. The simulation data suggest that hearing preservation in the implanted ear for bimodal CI listeners may significantly benefit utilization of spatial cues to segregate competing speech, especially when the residual acoustic hearing is comparable across two ears. Also, the benefits of bilateral residual acoustic hearing may be best ascertained for spatially separated maskers.

双模人工耳蜗（CI）使用者难以利用空间线索来分离竞争的语音，这可能是由于声学输入频率与刺激电极位置之间的音调拓扑失配所致。本研究在非人工耳蜗耳有残余听力或双耳都有残余听力的情况下，研究了音调拓扑失配的影响。在听力正常的成年人聆听人工耳蜗的声学模拟时，使用两个共定位或空间分离的言语掩蔽器测量了言语识别阈值（SRT）；低频声学信息在非人工耳蜗耳（双模聆听）或双耳中都可获得。对于共定位和空间分离的言语掩蔽器，音调拓扑匹配的双模SRT都明显优于失配的电听觉。当不存在音调拓扑失配时，当掩蔽器空间分离时，双耳的残余听力有显著益处，但当掩蔽器共定位时则没有。模拟数据表明，对于双模人工耳蜗使用者，植入耳的听力保留可能对利用空间线索分离竞争语音有显著益处，尤其是当双耳的残余听力相当时。此外，对于空间分离的掩蔽器，可能最能确定双耳残余听力的益处。