NON-LINEAR GAIN MEDIATING CORTICAL STIMULUS-RESPONSE RELATIONS
NON-LINEAR GAIN MEDIATING CORTICAL STIMULUS-RESPONSE RELATIONS
复制标题
DOI：
10.1007/bf00337412
复制
发表时间：
1979-01-01
影响因子：
1.9
通讯作者：
FREEMAN, WJ
中科院分区：
文献类型：
--
作者：
FREEMAN, WJ
当单个孤立神经元因稳态去极化而偏向阈值时，它们响应随机输入而表现出放电可能性的非线性增加。这一特性适用于嗅球中的神经元，嗅球是皮层的一种特殊形式，其中稳态处于离心控制之下。这种非线性模型基于 2 个一阶微分方程，这些方程与 3 个状态变量相互关联：局部神经元群（子集）的脉冲模式 p 下的活动密度；波模式 u 的活动密度（平均树突电流）；以及中间变量 m，它可以被认为代表霍奇金-赫胥黎方程中定义的钠活化因子子集中的平均亚阈值。稳定的稳态条件位于 (p0,u0,m0)。假设： 非线性是静态的； m 随 u 呈指数增加；随着 m 的增加，p 逐渐接近最大值 pm； p.gtoreq。 0 与 p0、u0 和 m0 的稳态值彼此成线性比例。该模型通过麻醉和清醒动物（猫）嗅球的单位数据和脑电图记录进行测试和评估。它具有以下特性：有小信号近线性输入输出范围；对于大输入，存在双边饱和，即对于大 u ，定义为 dp/du 的增益接近于零；大输入 .+- 的渐近线。 u 不对称；输出范围根据 u0 变化，最重要的是，当 u > u0 时出现最大增益，因此正（兴奋）输入以非线性方式增加输出和增益。清醒动物嗅球中的大量神经元维持在敏感的非线性状态，该状态对应于拉什顿和霍奇金定义的对单个轴突的阈下局部反应的域。
Single isolated neurons show a nonlinear increase in likelihood of firing in response to random input when they are biased toward threshold by steady-state depolarization. This property holds for neurons in the olfactory bulb, a specialized form of cortex in which the steady state is under centrifugal control. A model for this nonlinearity is based on 2 first order differential equations that interrelate 3 state variables: activity density in the pulse mode p of a local population (subset) of neurons; activity density in the wave mode u (mean dendritic current); and an intervening variable m that may be thought to represent the average subthreshold value in the subset for the sodium activation factor as defined in the Hodgkin-Huxley equations. A stable steady state condition is posited at (p0,u0,m0). It is assumed that: the nonlinearity is static; m increases exponentially with u; p approaches a maximum pm asymptotically as m increases; p .gtoreq. 0 and the steady state values of p0, u0, and m0 are linearly proportional to each other. The model is tested and evaluated with data from unit and EEG recording in the olfactory bulb of anesthetized and waking animals (cats). It has the following properties: there is a small-signal near-linear input-output range; there is bilateral saturation for large input, i.e., the gain defined as dp/du approaches zero for large u ; the asymptotes for large input .+-. u are asymmetric; the range of output is variable depending on u0 and most important, the maximal gain occurs for u > u0, so that positive (excitatory) input increases the output and the gain in a nonlinear manner. Large numbers of neurons in the olfactory bulb of the waking animal are maintained in a sensitive nonlinear state that corresponds to the domain of the subthreshold local response to single axons as it is defined by Rushton and Hodgkin.