Leung L S, Yu H W
Departments of Physiology and Clinical Neurological Sciences, The University of Western Ontario, London, Ontario N6A 5A5, Canada.
J Neurophysiol. 1998 Mar;79(3):1592-6. doi: 10.1152/jn.1998.79.3.1592.
Sinusoidal currents of various frequencies were injected into hippocampal CA1 neurons in vitro, and the membrane potential responses were analyzed by cross power spectral analysis. Sinusoidal currents induced a maximal (resonant) response at a theta frequency (3-10 Hz) in slightly depolarized neurons. As predicted by linear systems theory, the resonant frequency was about the same as the natural (spontaneous) oscillation frequency. However, in some cases, the resonant frequency was higher than the spontaneous oscillation frequency, or resonance was found in the absence of spontaneous oscillations. The sharpness of the resonance (Q), measured by the peak frequency divided by the half-peak power bandwidth, increased from a mean of 0.44 at rest to 0.83 during a mean depolarization of 6.5 mV. The phase of the driven oscillations changed most rapidly near the resonant frequency, and it shifted about 90 degrees over the half-peak bandwidth of 8.4 Hz. Similar results were found using a sinusoidal function of slowly changing frequency as the input. Sinusoidal currents of peak-to-peak intensity of >100 pA may evoke nonlinear responses characterized by second and higher harmonics. The theta-frequency resonance in hippocampal neurons in vitro suggests that the same voltage-dependent phenomenon may be important in enhancing a theta-frequency response when hippocampal neurons are driven by medial septal or other inputs in vivo.
将不同频率的正弦电流注入体外培养的海马CA1神经元，并通过交叉功率谱分析来分析膜电位反应。在轻度去极化的神经元中，正弦电流在θ频率（3 - 10Hz）时诱导出最大（共振）反应。正如线性系统理论所预测的，共振频率与自然（自发）振荡频率大致相同。然而，在某些情况下，共振频率高于自发振荡频率，或者在没有自发振荡的情况下发现了共振现象。通过峰值频率除以半峰功率带宽来测量的共振锐度（Q），从静息时的平均0.44增加到平均去极化6.5mV时的0.83。驱动振荡的相位在共振频率附近变化最为迅速，并且在8.4Hz的半峰带宽内大约偏移90度。使用缓慢变化频率的正弦函数作为输入时也得到了类似的结果。峰峰值强度>100pA的正弦电流可能会引发以二次及更高次谐波为特征的非线性反应。体外海马神经元中的θ频率共振表明，当海马神经元在体内受到内侧隔区或其他输入驱动时，相同的电压依赖性现象可能在增强θ频率反应中起重要作用。
