French Andrew S, Torkkeli Päivi H
Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada.
Ann Biomed Eng. 2008 Jan;36(1):153-61. doi: 10.1007/s10439-007-9392-9. Epub 2007 Oct 19.
The power law of sensory adaptation was introduced more than 50 years ago. It is characterized by action potential adaptation that follows fractional powers of time or frequency, rather than exponential decays and corresponding frequency responses. Power law adaptation describes the responses of a range of vertebrate and invertebrate sensory receptors to deterministic stimuli, such as steps or sinusoids, and to random (white noise) stimulation. Hypotheses about the physical basis of power law adaptation have existed since its discovery. Its cause remains enigmatic, but the site of power law adaptation has been located in the conversion of receptor potentials into action potentials in some preparations. Here, we used pseudorandom noise stimulation and direct spectral estimation to show that simulations containing only two voltage activated currents can reproduce the power law adaptation in two types of spider mechanoreceptors. Identical simulations were previously used to explain the different responses of these two types of sensory neurons to step inputs. We conclude that power law adaptation results during action potential encoding by nonlinear combination of a small number of activation and inactivation processes with different exponential time constants.
感觉适应的幂律在五十多年前就被提出了。其特点是动作电位适应遵循时间或频率的分数幂，而不是指数衰减和相应的频率响应。幂律适应描述了一系列脊椎动物和无脊椎动物感觉受体对确定性刺激（如阶跃或正弦波）以及随机（白噪声）刺激的反应。自幂律适应被发现以来，关于其物理基础的假说就一直存在。其原因仍然不明，但在一些标本中，幂律适应的位点已被定位在受体电位向动作电位的转换过程中。在这里，我们使用伪随机噪声刺激和直接频谱估计来表明，仅包含两种电压激活电流的模拟可以重现两种类型蜘蛛机械感受器中的幂律适应。相同的模拟先前被用于解释这两种类型的感觉神经元对阶跃输入的不同反应。我们得出结论，幂律适应是在动作电位编码过程中，由少数具有不同指数时间常数的激活和失活过程的非线性组合产生的。
