Bilateral Cochlear Implants: Physiology and Psychophysics

描述（由申请人提供）：双侧人工耳蜗植入比单侧人工耳蜗植入更有利于声音定位和噪声中的语音接收，但双侧人工耳蜗（CI）使用者的双耳表现仍远低于正常水平，特别是在涉及耳际时差（ITD）的任务中，特别是在语前聋受试者中。目前神经生理学家和心理物理学家之间的合作旨在获得对影响双侧CIs的过渡段敏感性的刺激、神经、知觉和发育因素的基本了解，以便设计创新的刺激和康复策略，改善双耳表现。双侧植入的人类受试者的心理物理实验将与来自听觉中脑的单单元记录并行进行，在一个新的，清醒的双侧CIs兔子模型中，允许几个月的神经记录。具体目的1是研究是否可以通过适当的双侧CIs慢性电刺激逆转先前在新生儿耳聋动物中观察到的神经ITD敏感性异常。我们将比较早期接受各种类型的慢性电刺激的新生儿耳聋兔与接受最小刺激的dea兔的神经ITD敏感性。一些家兔将接受一种实验策略的刺激，这种实验策略是专门设计的，通过双侧CIs有效地传递ITD信息，而一些家兔将只接受在两次人工耳蜗植入之间的单侧耳聋期间发生的单侧刺激，当这些人工耳蜗是在单独的手术中进行的。新生儿耳聋、CIs控制电刺激和清醒动物纵向神经记录相结合，为研究双耳系统的发育可塑性提供了一种强有力的新方法。具体目标2是测试一种新方法，通过引入额外的载波脉冲以产生短脉冲间隔（ipi），克服在当今语音处理器中使用的高载波脉冲率下观察到的过渡段灵敏度严重退化。这种方法的动机是我们发现，在不规则脉冲序列中短ipi的神经元可以恢复仅对高速率周期性脉冲序列发生反应的神经元的放电和ITD敏感性。对于简单脉冲序列和调制脉冲序列，神经和感知的ITD灵敏度将在有短ipi和没有短ipi的情况下进行比较，这些脉冲序列类似于由具有语音音节输入的CI处理器产生的当前波形。总之，这些目标将增加我们对刺激参数和早期听觉经验如何影响双侧CIs表现的基本理解。它们可能会导致新的处理策略和双侧ci的康复程序，这些策略和程序可以在空间分离的声源的日常声学环境中更好地工作，并且可以适应耳聋患者的听觉经验和听觉剥夺的历史。

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.