Dynamic spike threshold reveals a mechanism for synaptic coincidence detection in cortical neurons in vivo
Dynamic spike threshold reveals a mechanism for synaptic coincidence detection in cortical neurons in vivo
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DOI：
10.1073/pnas.130200797
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发表时间：
2000-07-05
影响因子：
11.1
通讯作者：
Gray, CM
中科院分区：
文献类型：
--
作者：
Azouz, R;Gray, CM
皮层神经元对突触输入的时间很敏感。它们可以在毫秒的时间尺度上同步它们的放电，并以高时间精度跟踪快速的刺激波动。这些发现表明，皮层神经元对同步突触输入的敏感性增强，导致快速去极化。动作电位产生的电压门控电流可能提供了一种放大快速去极化的机制。我们通过分析在体细胞内记录的猫视皮层神经元膜电位波动与峰电位阈值之间的关系来验证这一假设。我们发现，视觉刺激引起广泛的变化，尖峰阈值，在很大程度上是由尖峰阈值和膜去极化率之前的尖峰之间的反比关系所造成的。我们还发现，尖峰阈值是负相关的动作电位upstroke的上升率，这表明，尖峰阈值的增加，从Na+通道的可用性下降的结果。通过使用一个简单的神经元模型，我们表明，电压门控Na+和K+电导赋予皮层神经元的快速去极化，产生同步兴奋性突触输入的敏感性增强。因此，负责动作电位产生的基本机制也增强了皮层神经元对同步突触输入的敏感性。
Cortical neurons are sensitive to the timing of their synaptic inputs. They can synchronize their firing on a millisecond time scale and follow rapid stimulus fluctuations with high temporal precision. These findings suggest that cortical neurons have an enhanced sensitivity to synchronous synaptic inputs that lead to rapid rates of depolarization. The voltage-gated currents underlying action potential generation may provide one mechanism to amplify rapid depolarizations. We have tested this hypothesis by analyzing the relations between membrane potential fluctuations and spike threshold in cat visual cortical neurons recorded intracellularly in vivo. We find that visual stimuli evoke broad variations in spike threshold that are caused in large part by an inverse relation between spike threshold and the rate of membrane depolarization preceding a spike. We also find that spike threshold is inversely related to the rate of rise of the action potential upstroke, suggesting that increases in spike threshold result from a decrease in the availability of Na+ channels. By using a simple neuronal model, we show that voltage-gated Na+ and K+ conductances endow cortical neurons with an enhanced sensitivity to rapid depolarizations that arise from synchronous excitatory synaptic inputs. Thus, the basic mechanism responsible for action potential generation also enhances the sensitivity of cortical neurons to coincident synaptic inputs.