Moortgat K T, Keller C H, Bullock T H, Sejnowski T J
Howard Hughes Medical Institute, Computational Neurobiology Laboratory, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
Proc Natl Acad Sci U S A. 1998 Apr 14;95(8):4684-9. doi: 10.1073/pnas.95.8.4684.
What are the limits and modulators of neural precision? We address this question in the most regular biological oscillator known, the electric organ command nucleus in the brainstem of wave-type gymnotiform fish. These fish produce an oscillating electric field, the electric organ discharge (EOD), used in electrolocation and communication. We show here that the EOD precision, measured by the coefficient of variation (CV = SD/mean period) is as low as 2 x 10(-4) in five species representing three families that range widely in species and individual mean EOD frequencies (70-1,250 Hz). Intracellular recording in the pacemaker nucleus (Pn), which commands the EOD cycle by cycle, revealed that individual Pn neurons of the same species also display an extremely low CV (CV = 6 x 10(-4), 0.8 micro sec SD). Although the EOD CV can remain at its minimum for hours, it varies with novel environmental conditions, during communication, and spontaneously. Spontaneous changes occur as abrupt steps (250 ms), oscillations (3-5 Hz), or slow ramps (10-30 s). Several findings suggest that these changes are under active control and depend on behavioral state: mean EOD frequency and CV can change independently; CV often decreases in response to behavioral stimuli; and lesions of one of the two inputs to the Pn had more influence on CV than lesions of the other input.
神经精确性的限制因素和调节因素是什么？我们在已知的最规则的生物振荡器——波形裸背电鳗目鱼类脑干中的电鳐命令核中探讨了这个问题。这些鱼会产生一个振荡电场，即用于电定位和通讯的电鳐放电（EOD）。我们在此表明，在代表三个科的五个物种中，通过变异系数（CV = 标准差/平均周期）测量的EOD精确性低至2×10⁻⁴，这些物种在物种和个体平均EOD频率（70 - 1250赫兹）方面差异很大。对逐周期控制EOD周期的起搏器核（Pn）进行细胞内记录发现，同一物种的单个Pn神经元也显示出极低的CV（CV = 6×10⁻⁴，标准差为0.8微秒）。虽然EOD CV可以在数小时内保持最低水平，但它会随新的环境条件、通讯过程以及自发地发生变化。自发变化表现为突然的阶跃（250毫秒）、振荡（3 - 5赫兹）或缓慢的斜坡变化（10 - 30秒）。几项研究结果表明，这些变化受到主动控制且依赖于行为状态：平均EOD频率和CV可以独立变化；CV通常会对行为刺激做出降低的反应；Pn的两个输入之一受损对CV的影响比另一个输入受损更大。
