Probing the cochlea with partial tripolar stimulation in cochlear implantees

描述（由申请人提供）：人工耳蜗是一种非常成功的神经义肢，可以增强或恢复严重听力受损者的听力。然而，人工耳蜗听者的表现差异很大，特别是在嘈杂的环境和频谱复杂的刺激，如音乐。病理学和影像学研究表明，表现变异性的两个来源是存活的螺旋神经节神经元的分布及其与单个CI电极的距离。提出的研究的目的是发展临床有用的程序，以确定耳蜗的非刺激区域。由此产生的功能图可以指导患者特定声音处理策略的产生，从而提高人工耳蜗听者的听觉能力。通过三种类型的心理物理和电生理实验来确定低功能人工耳蜗通道的位置。所有的实验都将使用一种新的电极结构，部分三极电极，来激活有限数量的神经元，类似于使用窄带刺激来评估听力受损听众的低功能声死区。部分三极结构是介于宽单极和窄三极结构之间的混合体，其中流过两个侧翼电极的电流可以被调节以改变电流在耳蜗中的传播。在第一个实验中，随着部分三极分数电流的变化，将测量整个植入阵列的检测阈值。当电流场较窄时，低功能通道将从具有相对高阈值的通道推断出来，并且阈值随小电流的变化将提供有关功能缺陷的空间范围的信息。在第二个实验中，心理物理调谐曲线将使用前向掩蔽程序获得，以提供更详细的耳蜗激活评估。与应用调谐曲线诊断声死区类似，测量调谐曲线的宽度和尖端位移将作为识别低功能人工耳蜗通道的一种方法。在第三个实验中，将记录诱发电位。诱发电位阈值和振幅增长函数将直接与不同部分三极电流分量得到的心理物理阈值和调谐曲线进行比较。一个显著的相关性将提示诱发电位程序，这是一个临床实用的技术，可以检测低功能通道。最终，这项研究的发现可能会导致可用于临床的患者特异性制图程序的发展。超过6万名严重听力损失的人安装了人工耳蜗，以恢复部分听觉能力。在本研究中，识别低功能人工耳蜗通道可以提高这些患者的语言和音乐感知能力。

DESCRIPTION (provided by applicant): Cochlear implants are highly successful neural prostheses that enhance or restore hearing to the severely hearing impaired. However, performance varies considerably among cochlear implant listeners, particularly in noisy environments and for spectrally complex stimuli like music. Pathology and imaging studies suggest that two sources of performance variability are the distribution of surviving spiral ganglion neurons and their distance from individual CI electrodes. The objective of the proposed study is to develop clinically useful procedures to determine non-stimulable regions of the cochlea. The resulting functional maps could guide the production of patient-specific sound processing strategies, leading to improvements in the auditory ability of cochlear implant listeners. Three types of psychophysical and electrophysiological experiments will be conducted to identify the location of low functioning cochlear implant channels. All experiments will use a novel electrode configuration, partial tripolar, to activate restricted populations of neurons, analogous to the use of narrowband stimuli for assessing low functioning acoustic dead regions in hearing impaired listeners. The partial tripolar configuration is a hybrid between the broad monopolar and narrow tripolar configurations, in which the fraction of current that flows to two flanking electrodes can be adjusted to change the spread of current in the cochlea. In the first experiment, detection thresholds will be measured across the implant array as the partial tripolar fractional current varies. Low functioning channels will be inferred from channels with relatively high thresholds when the current field is narrow and the change in threshold with fractional current will provide information about the spatial extent of the functional deficit. In the second experiment, psychophysical tuning curves will be obtained using a forward masking procedure to provide a more detailed assessment of cochlear activation. Similar to the application of tuning curves to diagnose acoustic dead regions, the widths and tip shifts of the tuning curves will be measured as a way to identify low functioning cochlear implant channels. In the third experiment, evoked potentials will be recorded. Evoked potential thresholds and amplitude growth functions will be directly compared to psychophysical thresholds and tuning curves obtained with different partial tripolar current fractions. A significant correlation will suggest that the evoked potential procedure, which is a clinically practical technique, can detect low functioning channels. Ultimately, the findings of this study may lead to the development of a patient-specific mapping procedure that can be used clinically. Over 60,000 people with severe hearing loss have been fitted with cochlear implants to restore some auditory capabilities. Identifying low functioning cochlear implant channels in the proposed study could lead to the enhancement of speech and music perception in these patients.