Bilateral Cochlear Implants: Physiology and Psychophysics

描述（由申请人提供）：双侧人工耳蜗植入在噪声中的声音定位和语音接收方面优于单侧植入，但双侧人工耳蜗植入（CI）用户的双耳性能仍远低于正常，尤其是在涉及耳间时间差（ITD）的任务中，尤其是在语前聋受试者中。目前神经生理学家和精神病学家之间的合作旨在获得对影响ITD敏感性的刺激，神经，感知和发展因素的基本了解，以设计创新的刺激和康复策略，提高双耳性能。在双侧植入的人类受试者的心理物理学实验将与来自听觉中脑的单单位记录平行进行，该记录在一种新型的双侧CI的清醒兔模型中进行，该模型允许神经记录持续数月。具体目标1是调查是否可以通过适当的慢性电刺激通过双边CI逆转神经ITD敏感性的异常先前观察到的耳聋动物。我们将比较从幼年开始接受各种类型的慢性电刺激的麻醉家兔的神经ITD敏感性与接受最小刺激的dea家兔的敏感性。一些家兔将接受专门设计用于通过双侧CI有效传递ITD信息的实验策略的刺激，而一些家兔将仅接受单侧刺激，如在单独手术中进行的两次耳蜗植入之间的单侧耳聋期间发生的刺激。新生儿震耳欲聋，通过CI和纵向神经记录清醒动物的控制电刺激的组合提供了一个强大的新方法，用于研究双耳系统的发育可塑性。 具体目标2是测试一种新的方法，通过引入额外的载波脉冲以产生短的脉冲间间隔（IPI），来克服在当今语音处理器中使用的高载波脉冲速率下观察到的ITD灵敏度的严重退化。这种方法的动机是我们发现，在不规则脉冲串中缩短IPI的神经元可以恢复神经元中的放电和ITD敏感性，这些神经元只对高速率周期性脉冲串的开始做出反应。神经和感知ITD的灵敏度将进行比较，有和没有短IPI的简单脉冲串和调制脉冲串类似的电流波形与语音音节输入的CI处理器产生的。总之，这些目标将增加我们对刺激参数和早期听觉体验如何塑造双侧CI表现的基本理解。他们可能会导致新的处理策略和康复程序的双边CI，更好地工作在日常的声学环境与空间分离的声源，并适应历史的听觉经验和剥夺个别聋人患者。

DESCRIPTION (provided by applicant): Bilateral cochlear implantation provides benefits over unilateral implantation for sound localization and speech reception in noise, yet binaural performance of bilateral cochlear implant (CI) users is still well below normal, especially in task involving interaural time differences (ITD), and especially in pre-lingually deaf subjects. The present collaboration between neurophysiologists and psychophysicists aims at gaining a basic understanding of the stimulus, neural, perceptual and developmental factors that influence ITD sensitivity with bilateral CIs in order to devise innovative stimulation and rehabilitation strateges that improve binaural performance. Psychophysical experiments in bilaterally-implanted human subjects will be conducted in parallel with single-unit recordings from the auditory midbrain in a novel, awake rabbit model of bilateral CIs that allows neural recordings over several months. Specific Aim 1 is to investigate whether the abnormalities in neural ITD sensitivity previously observed in neonatally deaf animals can be reversed by appropriate chronic electric stimulation through bilateral CIs. We will compare neural ITD sensitivity in neonatally-deafened rabbits that receive various types of chronic electric stimulation from an early age with the sensitivity in dea rabbits that receive minimal stimulation. Some of the rabbits will receive stimulation with an experimental strategy that was specifically designed to deliver ITD information effectively with bilateral CIs, and some rabbits will only receive unilateral stimulation as occurs during the perio of unilateral deafness between the two cochlear implantations when these are performed in separate operations. The combination of neonatal deafening, controlled electric stimulation through CIs and longitudinal neural recording in awake animals offers a powerful new approach for studying the developmental plasticity of the binaural system. Specific Aim 2 is to test a new approach for overcoming the severe degradation in ITD sensitivity observed at the high carrier pulse rates used in today's speech processors by introducing additional carrier pulses so as to create short interpulse intervals (IPIs). This approach is motivated by our finding that neurons that short IPIs in irregular pulse trains can restore firing and ITD sensitivity in neurons that ony respond to the onset of high-rate periodic pulse trains. Neural and perceptual ITD sensitivities will be compared with and without short IPIs for both simple pulse trains and modulated pulse trains resembling the current waveforms produced by CI processors with speech syllable inputs. Together, these aims will increase our basic understanding of how stimulation parameters and early auditory experience shape performance with bilateral CIs. They will likely lead to new processing strategies and rehabilitation procedures for bilateral CIs that work better in everyday acoustic environments with spatially separated sound sources, and that are adapted to the history of auditory experience and deprivation of individual deaf patients.