Wang Runxia, Gu Huaguang, Zhang Xinjing
School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, 200092 China.
School of Mathematics and Statistics, North China University of Water Resources and Electric Power, Zhengzhou, 450000 China.
Cogn Neurodyn. 2024 Apr;18(2):715-740. doi: 10.1007/s11571-023-10024-6. Epub 2023 Nov 28.
Neurons in the medial superior olive (MSO) exhibit high frequency responses such as subthreshold resonance, which is helpful to sensitively detect a small difference in the arrival time of sounds between two ears for precise sound localization. Recently, except for the high frequency depolarization resonance mediated by a low threshold potassium () current, a low frequency hyperpolarization resonance mediated by a hyperpolarization-activated cation () current is observed in experiments on the MSO neurons, forming double resonances. The complex dynamics underlying double resonances are studied in an MSO neuron model in the present paper. Firstly, double resonances similar to the experimental observations are simulated as the resting membrane potential is between half-activation voltages of and currents, and stimulation current () with large amplitude and exponentially increasing frequency is applied. Secondly, multiple effective factors to modulate double resonances are obtained. Especially, the decrease of time constant of current and increase of conductance of and currents can enhance the depolarization resonance frequency for precise sound localization. Last, different frequency responses of slow and fast currents in formation of the resonances are acquired. A middle phase difference between and currents appears at a high frequency, and the interaction between the positive part of and the negative current forms the depolarization resonance. Interaction between the negative part of and positive current with a middle phase difference results in hyperpolarization resonance at a low frequency. Furthermore, the phase difference between and resonance current can well explain the increase of depolarization resonance frequency modulated by the increase of conductance of or currents. The results present the dynamical and biophysical mechanisms for the double resonances mediated by two currents in the MSO neurons, which is helpful to enhance the depolarization resonance frequency for precise sound localization.
内侧上橄榄核（MSO）中的神经元表现出高频响应，如阈下共振，这有助于灵敏地检测两耳声音到达时间的微小差异，以实现精确的声音定位。最近，除了由低阈值钾（）电流介导的高频去极化共振外，在MSO神经元实验中还观察到由超极化激活阳离子（）电流介导的低频超极化共振，形成了双共振。本文在一个MSO神经元模型中研究了双共振背后的复杂动力学。首先，当静息膜电位处于和电流的半激活电压之间，并施加大幅度且频率呈指数增加的刺激电流（）时，模拟出与实验观察结果相似的双共振。其次，获得了多个调节双共振的有效因素。特别是，电流时间常数的减小以及和电流电导的增加可以提高去极化共振频率，以实现精确的声音定位。最后，获得了慢电流和快电流在共振形成过程中的不同频率响应。在高频时，和电流之间出现中间相位差，电流的正部分与负电流之间的相互作用形成去极化共振。负部分与具有中间相位差的正电流之间的相互作用导致低频时的超极化共振。此外，和共振电流之间的相位差可以很好地解释由或电流电导增加所调制的去极化共振频率的增加。这些结果展示了MSO神经元中由两种电流介导的双共振的动力学和生物物理机制，这有助于提高去极化共振频率以实现精确的声音定位。
