Bilateral Cochlear Implants: Physiology and Psychophysics

描述(申请人提供)：在噪声中，双侧人工耳蜗术在声音定位和语音接收方面比单侧人工耳蜗术更有优势，但双侧人工耳蜗术者的双耳表现仍远低于正常，尤其是在涉及耳间时间差(ITD)的任务中，尤其是在语言先聋的受试者中。目前神经生理学家和心理生理学家之间的合作旨在通过双边顺应性刺激对影响ITD敏感性的刺激、神经、知觉和发育因素有一个基本的了解，以便设计出创新的刺激和康复策略来改善双耳的表现。在双侧植入的人类受试者中，心理物理实验将与听觉中脑的单个单位记录并行进行，在一个新颖的、清醒的双侧CI兔子模型中，可以进行几个月的神经记录。具体目的1是研究是否可以通过双侧顺式电刺激来逆转以前在新生儿耳聋动物中观察到的神经ITD敏感性的异常。我们将比较从小接受各种慢性电刺激的新生耳聋兔的神经ITD敏感性与接受微刺激的DEA兔的敏感性。其中一些兔将接受专门设计的实验策略的刺激，该策略旨在通过双侧CI有效地传递ITD信息，而一些兔将仅接受单侧刺激，如在两个人工耳蜗术后的单侧耳聋期间发生的那样，这些刺激是在单独的手术中进行的。新生儿耳聋、顺式可控电刺激和清醒动物纵向神经记录的结合为研究双耳系统的发育可塑性提供了有力的新途径。具体目标2是测试一种新的方法，用于通过引入额外的载波脉冲来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ITD灵敏度的严重下降，从而产生较短的脉冲间间隔(IPI)。这种方法的动机是我们发现，在不规则脉冲串中缩短IPI的神经元可以恢复对高频率周期性脉冲串开始唯一反应的神经元的放电和ITD敏感性。对于简单脉冲串和调制脉冲串，神经和知觉ITD敏感性将进行比较，包括简单脉冲串和调制脉冲串，这些脉冲串类似于具有语音音节输入的CI处理器产生的当前波形。总而言之，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边CI的表现的基本理解。它们可能会导致新的处理策略和双边CI的康复程序，这些策略和程序在具有空间分离声源的日常声学环境中更好地工作，并适应听觉经验的历史和聋人个体的剥夺。

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.