更改

=== 时间过滤 ===

== 时间过滤 ==

上述分析仅描述了具有稳态发射率的神经群体发射。当前突触群体发射率随时间任意变化时，可以使用Eq. \ref{poisson}来推导动态突触的过滤特性。在[[#附录A：短期抑制的时间过滤器推导|附录A]]中，我们为以抑制为主的突触（<math>u^+ \approx U</math>）提出了相应的计算。考虑围绕恒定率$R_0>0$的小幅度扰动$R(t):=R_0 + R_1 \rho (t)$，其中$R_1\ll R_0$，突触电流$I$的傅立叶变换可以近似为

上述分析仅描述了具有稳态发射率的神经群体发射。当前突触群体发射率随时间任意变化时，可以使用Eq. \ref{poisson}来推导动态突触的过滤特性。在[[#附录A：短期抑制的时间过滤器推导|附录A]]中，我们为以抑制为主的突触（<math>u^+ \approx U</math>）提出了相应的计算。考虑围绕恒定率$R_0>0$的小幅度扰动$R(t):=R_0 + R_1 \rho (t)$，其中$R_1\ll R_0$，突触电流$I$的傅立叶变换可以近似为

通过结合STD和STF，可以进一步改善神经信息传输。例如，通过结合以STF为主的兴奋性突触和以STD为主的抑制性突触，可以增强突触后神经元对高频时段的检测。在接收到以STD为主和以STF为主的输入的突触后神经元中，神经反应可以显示出低通和高通过滤特性。

通过结合STD和STF，可以进一步改善神经信息传输。例如，通过结合以STF为主的兴奋性突触和以STD为主的抑制性突触，可以增强突触后神经元对高频时段的检测。在接收到以STD为主和以STF为主的输入的突触后神经元中，神经反应可以显示出低通和高通过滤特性。

===增益控制Gain control===

== 增益控制Gain control ==

 

Since STD suppresses synaptic efficacy in a frequency-dependent manner, it has been suggested that STD provides an automatic mechanism to achieve gain control, namely, by assigning high gain to slowly firing afferents and low gain to rapidly firing afferents ([[#Abbott97|Abbott 97]], [[#Abbott04|Abbott 04]], [[#Cook03|Cook 03]]). If a steady presynaptic firing rate <math>R</math> changes abruptly by an amount <math>\Delta R</math>, the first spike at the new rate will be transmitted with the efficacy <math>E</math> before the synapse is further depressed. Thus, the transient increase in synaptic input will be proportional to <math>\Delta R E(R)</math>, which is approximately proportional to <math>\Delta R/R</math> for large rates (see above).  This is reminiscent of Weber’s law, which states that a transient synaptic response is roughly proportional to the percentage change of the input firing rate. Fig. 2D shows that for a fixed-size rate change <math>\Delta R</math>, the response decreases as a function of the steady input value; whereas without STD, the response would be constant for a fixed-size rate change.

Since STD suppresses synaptic efficacy in a frequency-dependent manner, it has been suggested that STD provides an automatic mechanism to achieve gain control, namely, by assigning high gain to slowly firing afferents and low gain to rapidly firing afferents ([[#Abbott97|Abbott 97]], [[#Abbott04|Abbott 04]], [[#Cook03|Cook 03]]). If a steady presynaptic firing rate <math>R</math> changes abruptly by an amount <math>\Delta R</math>, the first spike at the new rate will be transmitted with the efficacy <math>E</math> before the synapse is further depressed. Thus, the transient increase in synaptic input will be proportional to <math>\Delta R E(R)</math>, which is approximately proportional to <math>\Delta R/R</math> for large rates (see above).  This is reminiscent of Weber’s law, which states that a transient synaptic response is roughly proportional to the percentage change of the input firing rate. Fig. 2D shows that for a fixed-size rate change <math>\Delta R</math>, the response decreases as a function of the steady input value; whereas without STD, the response would be constant for a fixed-size rate change.