Leake P A, Snyder R L, Rebscher S J, Moore C M, Vollmer M
Department of Otolaryngology, Epstein Laboratory, Room U490, University of California San Francisco, 533 Parnassus Avenue, San Francisco, CA 94143-0526, USA.
Hear Res. 2000 Sep;147(1-2):221-41. doi: 10.1016/s0378-5955(00)00133-7.
The goal of this research is to examine the functional consequences of patterned electrical stimulation delivered by a cochlear implant in the deafened developing auditory system. In previous electrophysiological experiments conducted in the inferior colliculus (IC), we have demonstrated that the precise cochleotopic organization of the central nucleus (ICC) develops normally in neonatally deafened unstimulated cats and is unaltered despite the lack of normal auditory input during development. However, these studies also showed that chronic electrical stimulation delivered at a single intracochlear location by one bipolar channel of a cochlear implant induces significant expansion of the central representation of the stimulated cochlear sector and degrades the cochleotopic organization of the IC. This report presents additional data from a new experimental series of neonatally deafened cats that received chronic stimulation on two adjacent bipolar intracochlear channels of a cochlear implant. Results suggest that competing inputs elicited by electrical stimulation delivered by two adjacent channels can maintain the selective representations of each activated cochlear sector within the central auditory system and prevent the expansion seen after single-channel stimulation. Alternating stimulation of two channels and use of highly controlled electrical signals may be particularly effective in maintaining or even sharpening selectivity of central representations of stimulated cochlear sectors. In contrast, simultaneous stimulation using two channels of a model analog cochlear implant processor in one experimental animal failed to maintain channel selectivity and resulted in marked expansion and fusion of the central representations of the stimulated channels. This potentially important preliminary result suggests that under some conditions the central auditory system may be unable to discriminate simultaneous, overlapping inputs from adjacent cochlear implant channels as distinct.
本研究的目标是检验人工耳蜗传递的模式化电刺激在发育中的听觉系统失聪后所产生的功能后果。在先前在下丘（IC）进行的电生理实验中，我们已经证明，在新生期致聋且未受刺激的猫中，中央核（ICC）精确的耳蜗拓扑组织正常发育，并且尽管在发育过程中缺乏正常的听觉输入，其仍未改变。然而，这些研究还表明，通过人工耳蜗的一个双极通道在单个耳蜗内位置进行的慢性电刺激会导致受刺激耳蜗区域的中枢表征显著扩展，并破坏IC的耳蜗拓扑组织。本报告展示了来自一系列新实验的额外数据，这些实验针对新生期致聋的猫，通过人工耳蜗的两个相邻双极耳蜗内通道进行慢性刺激。结果表明，由两个相邻通道传递的电刺激引发的竞争性输入可以在中枢听觉系统内维持每个激活的耳蜗区域的选择性表征，并防止单通道刺激后出现的扩展。交替刺激两个通道以及使用高度可控的电信号可能在维持甚至增强受刺激耳蜗区域的中枢表征的选择性方面特别有效。相比之下，在一只实验动物中使用模拟人工耳蜗处理器的两个通道进行同时刺激未能维持通道选择性，并导致受刺激通道的中枢表征明显扩展和融合。这一潜在重要的初步结果表明，在某些情况下，中枢听觉系统可能无法区分来自相邻人工耳蜗通道的同时、重叠输入。
