Using current-focusing and current-steering to increase the number of effective c

描述（由申请人提供）：本研究的总体目标是制定刺激策略，增加人工耳蜗（CI）使用者的有效通道数量。由于植入设备的频谱分辨率有限，大多数CI用户在具有挑战性的听力条件下（例如，背景噪声、竞争语音、音乐等）都有很大的困难。虽然当代CI设备可以传输多达22个物理通道（以及更多的虚拟通道），但CI用户通常只能访问~8个通道。我们假设CI用户的功能光谱分辨率主要受到通道相互作用的限制，即通道之间的电流扩散。减少电流扩散的一种方法是利用三极和/或四极刺激模式（电流聚焦）。然而，即使22个完全独立的物理通道也不足以支持具有挑战性的听力任务。增加通道数量超过物理电极数量的一种方法是同时刺激相邻电极，创建虚拟通道（电流转向）。我们建议将电流聚焦与电流转向相结合，以提高CI用户的功能光谱分辨率。如果成功，在信号处理策略中结合电流聚焦和电流转向，可能使CI用户能够访问困难收听条件所需的额外频谱通道。为了成功地实施这种策略，重要的是要发展当前聚焦和当前转向的基本心理物理框架。以下三个具体目标是收集开发下一代声音处理策略所需的基本信息。

DESCRIPTION (provided by applicant): The overall goal of this research is to develop stimulation strategies that increase the number of effective channels for cochlear implant (CI) users. Most CI users have great difficulty in challenging listening conditions (e.g., background noise, competing speech, music, etc.), due to the limited spectral resolution of the implant device. While contemporary CI devices can transmit as many as 22 physical channels (and many more virtual channels), CI users can typically access only ~8 channels. We hypothesize that CI users' functional spectral resolution is primarily limited by channel interactions, i.e., the electrical current spread between channels. One approach to reduce current spread is to utilize tripolar and/or quadrupolar stimulation modes (current focusing). However, even 22 fully independent physical channels are not sufficient to support challenging listening tasks. One approach to increase the number of channels beyond the physical number of electrodes is to simultaneously stimulate adjacent electrodes, creating virtual channels (current steering). We propose to combine current focusing with current steering to improve CI users' functional spectral resolution. If successful, combining current focusing and current steering within a signal processing strategy may allow CI users to access the additional spectral channels needed for difficult listening conditions. In order to successfully implement such a strategy, it is important to develop the basic psychophysical framework of current focusing and current steering. The following three specific aims are to collect the basic information needed to develop the next generation sound processing strategy. In Specific Aim 1, we will compare the current spread between loudness balanced stimuli with differing degrees of current focusing. We predict that for a fixed loudness level, current spread will be significantly reduced for focused stimuli. If so, focused stimulation in a signal processing strategy should reduce channel interaction and improve the functional spectral resolution. In Specific Aim 2, we will investigate perceptual effects associated with different degrees of current focusing. Anecdotal reports suggest that current focusing may result in changes in pitch (Saoji, 2007; Berenstein, 2007) and/or tonal clarity (Marzalek et al., 2007). We predict that increased focusing will provide a small but reliable improvement in tonal clarity, but will not systematically alter the perceived pitch. In Specific Aim 3, we will measure discrimination of current-steered virtual channels that can be generated between two electrodes with and without current focusing. We predict that spatial selectivity for virtual channels will be significantly improved with current focusing. Relevance: While contemporary cochlear implants (CIs) can transmit as many as 22 physical channels (and many more virtual channels), hearing impaired patients with CIs can typically access only ~8 channels. Challenging listening conditions (e.g., speech in noise, competing speech, music, etc) require significantly more channels. The proposed research is clinically relevant, as it addresses a long-standing challenge in CI research: how to increase the number of effective spectral channels.