Section of Neurobiology and Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712, USA.
Neuron. 2013 Jun 5;78(5):923-35. doi: 10.1016/j.neuron.2013.04.022.
Feedforward inhibition sharpens the precision of neurons throughout ascending auditory pathways, including the binaural neurons of the medial superior olive (MSO). However, the biophysical influence of inhibition is poorly understood, particularly at higher frequencies at which the relative phase of inhibition and excitation becomes ambiguous. Here, we show in gerbil MSO principal cells in vitro that feedforward inhibition precedes direct excitation, providing a concurrent hyperpolarization and conductance shunt during EPSP summation. We show with dual-patch recordings and dynamic clamp that both the linearity and temporal fidelity of synaptic integration is improved by reducing Kv1 potassium channel conductance during inhibition, which counters membrane shunting even at high frequencies at which IPSPs sum. The reduction of peak excitation by preceding inhibition lowers spike probability, narrowing but not shifting the window for detecting binaural coincidence. The interplay between inhibition and potassium conductances thus improves the consistency and resolution of ITD coding across different frequencies.
前馈抑制作用会增强上行听觉通路上包括内侧上橄榄核（MSO）在内的双音频神经元的精度。然而，抑制作用的生物物理影响还知之甚少，尤其是在更高频率下，抑制和兴奋的相对相位变得模糊。在这里，我们在体外的沙鼠 MSO 主细胞中显示，前馈抑制作用先于直接兴奋，在 EPSP 总和过程中提供同时的超极化和电导分流。我们通过双膜片钳记录和动态钳位实验表明，通过在抑制期间降低 Kv1 钾通道电导，可改善突触整合的线性和时间保真度，即使在高频时 IPSP 总和时，也能对抗膜分流。前馈抑制对峰值兴奋的抑制降低了尖峰的概率，缩小但没有改变检测双耳同时的窗口。因此，抑制和钾电导之间的相互作用可提高不同频率下 ITD 编码的一致性和分辨率。
