A balance between synaptic excitation and inhibition (E/I balance) maintained within a narrow window is widely regarded to be crucial for cortical processing. In line with this idea, the E/I balance is reportedly comparable across neighboring neurons, behavioral states, and developmental stages and altered in many neurological disorders. Motivated by these ideas, we examined whether synaptic inhibition changes over the 24-h day to compensate for the well-documented sleep-dependent changes in synaptic excitation. We found that, in pyramidal cells of visual and prefrontal cortices and hippocampal CA1, synaptic inhibition also changes over the 24-h light/dark cycle but, surprisingly, in the opposite direction of synaptic excitation. Inhibition is upregulated in the visual cortex during the light phase in a sleep-dependent manner. In the visual cortex, these changes in the E/I balance occurred in feedback, but not feedforward, circuits. These observations open new and interesting questions on the function and regulation of the E/I balance.

中文翻译：

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视觉皮层电路中兴奋-抑制平衡的每日振荡。

维持在狭窄窗口内的突触兴奋和抑制（E/I 平衡）之间的平衡被广泛认为对皮层处理至关重要。根据这一想法，据报道，E/I 平衡在相邻神经元、行为状态和发育阶段之间具有可比性，并且在许多神经系统疾病中发生了改变。受这些想法的启发，我们检查了突触抑制是否在 24 小时内发生变化，以补偿有充分记录的突触兴奋的睡眠依赖性变化。我们发现，在视觉和前额叶皮质以及海马 CA1 的锥体细胞中，突触抑制也在 24 小时光/暗周期中发生变化，但令人惊讶的是，突触兴奋的方向相反。在光照阶段，视觉皮层的抑制作用以睡眠依赖的方式上调。在视觉皮层，E/I 平衡的这些变化发生在反馈电路中，而不是前馈电路中。这些观察结果为 E/I 平衡的功能和调节提出了新的有趣问题。