Pfeiffer Keram, French Andrew S
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada.
J Neurosci. 2009 Sep 2;29(35):10989-94. doi: 10.1523/JNEUROSCI.2744-09.2009.
Neurotransmitter chemicals excite or inhibit a range of sensory afferents and sensory pathways. These changes in firing rate or static sensitivity can also be associated with changes in dynamic sensitivity or membrane noise and thus action potential timing. We measured action potential firing produced by random mechanical stimulation of spider mechanoreceptor neurons during long-duration excitation by the GABAA agonist muscimol. Information capacity was estimated from signal-to-noise ratio by averaging responses to repeated identical stimulation sequences. Information capacity was also estimated from the coherence function between input and output signals. Entropy rate was estimated by a data compression algorithm and maximum entropy rate from the firing rate. Action potential timing variability, or jitter, was measured as normalized interspike interval distance. Muscimol increased firing rate, information capacity, and entropy rate, but jitter was unchanged. We compared these data with the effects of increasing firing rate by current injection. Our results indicate that the major increase in information capacity by neurotransmitter action arose from the increased entropy rate produced by increased firing rate, not from reduction in membrane noise and action potential jitter.
神经递质化学物质会兴奋或抑制一系列感觉传入神经和感觉通路。放电频率或静态敏感性的这些变化也可能与动态敏感性或膜噪声的变化相关，进而与动作电位的时间相关。我们在由GABAA激动剂蝇蕈醇进行的长时间兴奋过程中，测量了蜘蛛机械感受器神经元随机机械刺激所产生的动作电位发放。通过对重复相同刺激序列的反应进行平均，根据信噪比估计信息容量。信息容量还通过输入和输出信号之间的相干函数来估计。熵率通过数据压缩算法估计，最大熵率则根据放电频率估计。动作电位时间变异性或抖动，通过归一化的峰峰间期距离来测量。蝇蕈醇增加了放电频率、信息容量和熵率，但抖动未变。我们将这些数据与通过电流注入增加放电频率的效果进行了比较。我们的结果表明，神经递质作用导致的信息容量的主要增加源于放电频率增加所产生的熵率增加，而非膜噪声和动作电位抖动的降低。
