Noise-induced transition to bursting in responses of paddlefish electroreceptor afferents.
Noise-induced transition to bursting in responses of paddlefish electroreceptor afferents.
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DOI：
10.1152/jn.01289.2006
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发表时间：
2007-11
影响因子：
2.5
通讯作者：
A. Neiman;T. Yakusheva;D. F. Russell
中科院分区：
文献类型：
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作者：
A. Neiman;T. Yakusheva;D. F. Russell
在活体条件下，研究了白鳍壶腹电感受器对不同强度的噪声波形(均为高斯型和零均值)的单单位传入反应特性。它们包括宽带白噪声、Ornstein-Uhlenbeck噪声、低频带或高频带限噪声，或从成群的浮游动物猎物或从单个猎物记录的自然噪声。正常情况下，传入神经以一种紧张的方式自发放电，这实际上是准周期的，因为嵌入了振荡器。1)弱噪声刺激增加了传入放电的变异性，但仍保持紧张性。2)相反，较弱的宽带噪声刺激使放电模式发生质的变化，出现抛物线爆发，而平均放电频率几乎没有变化。3)在向传入爆发的转变过程中，出现了两个独立的时间尺度：爆发内快频率约为250次/S，爆发慢频率约为9次(5-13)次/S，这两个时间尺度在传入功率谱、双峰峰间期直方图、回归图和传入穗序列的自相关函数中表现为两种状态。4)随机的大约9赫兹的脉冲串不是简单地由噪声刺激的相似频率分量驱动的，因为使用高通滤波噪声或0.1赫兹正弦波刺激可以将脉冲串与刺激波形分离。5)Arrhenius曲线图显示，诱发猝发所需的阈值噪声强度取决于噪声刺激的频率含量，对于与这些阴极兴奋的壶腹电感受器的1-20赫兹最佳反应带匹配的刺激，阈值噪声强度最低，约为1.2微V/cm。这只比之前对电感觉阈值的行为估计略高，为0.5微伏/厘米。6)爆发的可比阈值来自另一种分析方法，该方法基于脉冲序列的相关时间。7)对传入神经元的同步记录表明，随着噪声刺激幅度的增大，它们的爆发频率(爆发数/S)总是收敛的。因此，对于不同的电感受器，爆发的缓慢时间尺度是相似的，尽管它们的平均尖峰频率可能不同。总而言之，白鳍豚的壶腹电感受器有两种截然不同的工作模式：它们的自发紧张性放电受到最弱刺激的调制，但它们会在较弱的刺激下切换到爆发性输出。我们认为，传入爆发可能介导了对浮游猎物的近距离跟踪。
The response properties of ampullary electroreceptors of paddlefish, Polyodon spathula, were studied in vivo, as single-unit afferent responses to external electrical stimulation with varied intensities of several types of noise waveforms, all Gaussian and zero-mean. They included broadband white noise, Ornstein-Uhlenbeck noise, low- or high-frequency band-limited noise, or natural noise recorded from swarms of Daphnia zooplankton prey, or from individual prey. Normally the afferents fire spontaneously in a tonic manner, which is actually quasiperiodic due to embedded oscillators. 1) Weak noise stimuli increased the variability of afferent firing, but it remained tonic. 2) In contrast, stimulation with less-weak broadband noise led to a qualitative change of the firing patterns, to parabolic bursting, even though the mean firing rate was scarcely affected. 3) The transition to afferent bursting was marked by the development of two well-separated timescales: the fast frequency of spiking inside bursts at <or=250 spikes/s and the slow frequency of burst occurrences at about 9 (range 5-13) bursts/s. These two timescales were manifested as two regimes in afferent power spectra, bimodal interspike interval histograms, return maps, and autocorrelation functions of afferent spike trains. 4) The stochastic approximately 9-Hz bursts were not simply driven by similar-frequency components of noise stimuli because bursts could be dissociated from stimulus waveforms using high-pass filtered noise, or a 0.1-Hz sine-wave stimulus. 5) Arrhenius plots showed that the threshold noise intensity required to elicit bursting depended on the frequency content of a noise stimulus, being lowest, about 1.2 microV/cm, for stimuli matching the 1- to 20-Hz best response band of these cathodally excited ampullary electroreceptors. This is only slightly higher than previous behavioral estimates of the electrosensory threshold as 0.5 microV/cm. 6) Comparable threshold values for bursting came from an alternate analytical approach, based on correlation times of spike trains. 7) Simultaneous recordings from pairs of afferents showed that their bursting frequencies (bursts/s) always converged as the amplitude of a noise stimulus was raised. Thus the slow timescale of bursting is similar for different electroreceptors, even though their mean spiking rates can differ. In conclusion, the ampullary electroreceptors of paddlefish have two distinct modes of operation: their spontaneous tonic firing is modulated by the weakest stimuli, but they switch to bursting output for less-weak stimuli. We propose that afferent bursting may mediate close-range tracking of planktonic prey.