Diversity of gain modulation by noise in neocortical neurons: Regulation by the slow afterhyperpolarization conductance
Diversity of gain modulation by noise in neocortical neurons: Regulation by the slow afterhyperpolarization conductance
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DOI：
10.1523/jneurosci.1792-06.2006
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发表时间：
2006-08-23
影响因子：
5.3
通讯作者：
Spain, William J.
中科院分区：
文献类型：
--
作者：
Higgs, Matthew H.;Slee, Sean J.;Spain, William J.
已知神经元放电依赖于突触输入的方差以及平均输入电流。几项研究表明，输入方差或“噪声”具有分裂效应，降低了触发频率-电流（f-I）关系的斜率或增益。我们测量了电流噪声对大鼠感觉运动皮层切片中锥体神经元和快速尖峰（FS）中间神经元的f-I关系的影响。在大多数锥体神经元中，噪声对稳态f-I关系有倍增效应，增加增益。相反，噪声降低FS中间神经元的增益。锥体神经元的增益增强随着刺激持续时间的增加而增加，并且与慢后超极化（sAHP）的幅度相关，sAHP是尖峰频率适应的主要机制。5-HT 2受体激动剂α-甲基-5-HT降低了sAHP并消除了增益增加，而通过尖峰触发的动态电流钳增加sAHP电导增强了增益增加。这些结果表明，噪声的影响从根本上不同类的新皮层神经元，这取决于特定的生物物理特性，包括sAHP电导。因此，来自背景突触输入的噪声可以通过增加具有大sAHPs的锥体神经元中的增益和减少抑制性FS中间神经元中的增益来增强网络兴奋性。
Neuronal firing is known to depend on the variance of synaptic input as well as the mean input current. Several studies suggest that input variance, or "noise," has a divisive effect, reducing the slope or gain of the firing frequency-current (f-I) relationship. We measured the effects of current noise on f-I relationships in pyramidal neurons and fast-spiking (FS) interneurons in slices of rat sensorimotor cortex. In most pyramidal neurons, noise had a multiplicative effect on the steady-state f-I relationship, increasing gain. In contrast, noise reduced gain in FS interneurons. Gain enhancement in pyramidal neurons increased with stimulus duration and was correlated with the amplitude of the slow afterhyperpolarization (sAHP), a major mechanism of spike-frequency adaptation. The 5-HT2 receptor agonist alpha-methyl-5-HT reduced the sAHP and eliminated gain increases, whereas augmenting the sAHP conductance by spike-triggered dynamic-current clamp enhanced the gain increase. These results indicate that the effects of noise differ fundamentally between classes of neocortical neurons, depending on specific biophysical properties including the sAHP conductance. Thus, noise from background synaptic input may enhance network excitability by increasing gain in pyramidal neurons with large sAHPs and reducing gain in inhibitory FS interneurons.