Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI 48109-5616, USA.
J Assoc Res Otolaryngol. 2010 Jun;11(2):245-65. doi: 10.1007/s10162-009-0194-7. Epub 2009 Nov 10.
Previous studies have shown that residual acoustic hearing supplements cochlear implant function to improve speech recognition in noise as well as perception of music. The current study had two primary objectives. First, we sought to determine how cochlear implantation and electrical stimulation over a time period of 14 to 21 months influence cochlear structures such as hair cells and spiral ganglion neurons. Second, we sought to investigate whether the structures that provide acoustic hearing also affect the perception of electrical stimulation. We compared psychophysical responses to cochlear implant stimulation in two groups of adult guinea pigs. Group I (11 animals) received a cochlear implant in a previously untreated ear, while group II (ten animals) received a cochlear implant in an ear that had been previously infused with neomycin to destroy hearing. Psychophysical thresholds were measured in response to pulse-train and sinusoidal stimuli. Histological analysis of all group I animals and a subset of group II animals was performed. Nine of the 11 group I animals showed survival of the organ of Corti and spiral ganglion neurons adjacent to the electrode array. All group I animals showed survival of these elements in regions apical to the electrode array. Group II animals that were examined histologically showed complete loss of the organ of Corti in regions adjacent and apical to the electrode array and severe spiral ganglion neuron loss, consistent with previous reports for neomycin-treated ears. Behaviorally, group II animals had significantly lower thresholds than group I animals in response to 100 Hz sinusoidal stimuli. However, group I animals had significantly lower thresholds than group II animals in response to pulse-train stimuli (0.02 ms/phase; 156 to 5,000 pps). Additionally, the two groups showed distinct threshold versus pulse rate functions. We hypothesize that the differences in detection thresholds between groups are caused by the electrical activation of the hair cells in group I animals and/or differences between groups in the condition of the spiral ganglion neurons.
先前的研究表明，残余听力补充人工耳蜗的功能，改善噪声下的言语识别能力和音乐感知能力。本研究有两个主要目的。首先，我们试图确定在 14 至 21 个月的时间内，人工耳蜗植入和电刺激如何影响毛细胞和螺旋神经节神经元等耳蜗结构。其次，我们试图研究提供听觉的结构是否也会影响对电刺激的感知。我们比较了两组成年豚鼠对人工耳蜗刺激的心理物理反应。第一组（11 只动物）在未治疗的耳朵中植入人工耳蜗，第二组（10 只动物）在先前用新霉素灌注以破坏听力的耳朵中植入人工耳蜗。我们用脉冲串和正弦刺激测量心理物理阈值。对所有第一组动物和第二组动物的一部分进行了组织学分析。第一组的 11 只动物中有 9 只显示出与电极阵列相邻的 Corti 器官和螺旋神经节神经元的存活。所有第一组动物都显示出这些元素在电极阵列上方区域的存活。经组织学检查的第二组动物显示，与电极阵列相邻和上方区域的 Corti 器官完全丧失，以及严重的螺旋神经节神经元丧失，与新霉素处理耳朵的先前报道一致。行为上，第二组动物对 100 Hz 正弦刺激的阈值明显低于第一组动物。然而，第一组动物对脉冲串刺激（0.02 ms/相；156 至 5000pps）的阈值明显低于第二组动物。此外，两组的阈值与脉冲率函数明显不同。我们假设两组之间的检测阈值差异是由第一组动物的毛细胞的电激活和/或两组之间螺旋神经节神经元状况的差异引起的。
