Department of Applied Mathematics, University of Washington, Seattle, WA, USA.
J Neurophysiol. 2012 Sep;108(5):1430-52. doi: 10.1152/jn.00095.2012. Epub 2012 Jun 6.
Model-based studies of responses of auditory nerve fibers to electrical stimulation can provide insight into the functioning of cochlear implants. Ideally, these studies can identify limitations in sound processing strategies and lead to improved methods for providing sound information to cochlear implant users. To accomplish this, models must accurately describe spiking activity while avoiding excessive complexity that would preclude large-scale simulations of populations of auditory nerve fibers and obscure insight into the mechanisms that influence neural encoding of sound information. In this spirit, we develop a point process model of individual auditory nerve fibers that provides a compact and accurate description of neural responses to electric stimulation. Inspired by the framework of generalized linear models, the proposed model consists of a cascade of linear and nonlinear stages. We show how each of these stages can be associated with biophysical mechanisms and related to models of neuronal dynamics. Moreover, we derive a semianalytical procedure that uniquely determines each parameter in the model on the basis of fundamental statistics from recordings of single fiber responses to electric stimulation, including threshold, relative spread, jitter, and chronaxie. The model also accounts for refractory and summation effects that influence the responses of auditory nerve fibers to high pulse rate stimulation. Throughout, we compare model predictions to published physiological data of response to high and low pulse rate stimulation. We find that the model, although constructed to fit data from single and paired pulse experiments, can accurately predict responses to unmodulated and modulated pulse train stimuli. We close by performing an ideal observer analysis of simulated spike trains in response to sinusoidally amplitude modulated stimuli and find that carrier pulse rate does not affect modulation detection thresholds.
基于模型的听觉神经纤维对电刺激反应的研究可以深入了解人工耳蜗的工作原理。理想情况下，这些研究可以识别声音处理策略的局限性，并为向人工耳蜗使用者提供声音信息的改进方法提供指导。为此，模型必须准确描述尖峰活动，同时避免过度复杂，从而排除大规模模拟听觉神经纤维群体并掩盖对影响声音信息神经编码机制的洞察力。本着这种精神，我们开发了一种个体听觉神经纤维的点过程模型，该模型对电刺激的神经反应提供了紧凑而准确的描述。受广义线性模型框架的启发，所提出的模型由一系列线性和非线性阶段组成。我们展示了如何将每个阶段与生物物理机制相关联，并与神经元动力学模型相关联。此外，我们推导出了一种半分析程序，可以根据单个纤维对电刺激反应的记录中的基本统计数据，唯一地确定模型中的每个参数，包括阈值、相对扩散、抖动和时程。该模型还考虑了影响听觉神经纤维对高脉冲率刺激反应的不应期和总和效应。在整个过程中，我们将模型预测与高脉冲率和低脉冲率刺激的生理数据进行比较。我们发现，尽管该模型是为拟合单脉冲和双脉冲实验的数据而构建的，但它可以准确预测未调制和调制脉冲串刺激的反应。最后，我们对模拟的尖峰序列对正弦幅度调制刺激的反应进行了理想观察者分析，并发现载波脉冲率不会影响调制检测阈值。
