Nonuniformity in the linear network model of the oculomotor integrator produces approximately fractional-order dynamics and more realistic neuron behavior
Nonuniformity in the linear network model of the oculomotor integrator produces approximately fractional-order dynamics and more realistic neuron behavior
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DOI：
10.1007/s004220050487
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发表时间：
1998-11-01
影响因子：
1.9
通讯作者：
Anastasio, TJ
中科院分区：
文献类型：
--
作者：
Anastasio, TJ
眼整合器是由前庭内侧核和脑干中的舌下前置核中的神经元组成的网络。这些神经元近似地充当各种阶的分数积分器，将眼睛速度命令转换成介于速度和位置之间的信号。动眼神经积分器被建模为线性神经元网络，其时间常数通过相互抑制的正反馈而延长。在这个模型中，每个神经元都以相同的高斯分布抑制其邻居，所有模型神经元都表现为相同的一阶低通滤波器，其动态与组成实际眼动积分器的神经元的近似分数阶动态不匹配。分数阶积分器可以近似为一阶低通滤波器的加权和，这些滤波器具有不同的、广泛分布的时间常数。动态系统分析表明，模型积分器确实有许多广泛分布的时间常数。然而，由于其网络连接的均匀性，在模型中仅表达一个时间常数。如果模型网络通过去除少量神经元之间的相互连接而变得不均匀，则会表达更多的时间常数。非均匀网络模型中的神经元的动力学是可变的，近似分数阶，并且类似于组成实际眼动积分器的神经元的动力学。完全移除与神经元之间的连接相当于消除它，这是之前为了证明积分器网络模型的鲁棒性而进行的操作。具有讽刺意味的是，由此产生的非均匀网络模型，以前被认为是代表一个病态的积分器，实际上可能代表一个健康的积分器，其中包含具有实际可变的神经元，近似分数阶动力学。
The oculomotor integrator is a network that is composed of neurons in the medial vestibular nuclei and nuclei prepositus hypoglossi in the brainstem. Those neurons act approximately as fractional integrators of various orders, converting eye velocity commands into signals that are intermediate between velocity and position. The oculomotor integrator has been modeled as a network of linear neural elements, the time constants of which are lengthened by positive feedback through reciprocal inhibition. In this model, in which each neuron reciprocally inhibits its neighbors with the same Gaussian profile, all model neurons behave as identical, first-order, low-pass filters with dynamics that do not match the variable, approximately fractional-order dynamics of the neurons that compose the actual oculomotor integrator. Fractional-order integrators can be approximated by weighted sums of first-order, low-pass filters with diverse, broadly distributed time constants. Dynamic systems analysis reveals that the model integrator indeed has many broadly distributed time constants. However, only one time constant is expressed in the model due to the uniformity of its network connections. If the model network is made nonuniform by removing the reciprocal connections to and from a small number of neurons, then many more time constants are expressed. The dynamics of the neurons in the nonuniform network model are variable, approximately fractional-order, and resemble those of the neurons that compose the actual oculomotor integrator. Completely removing the connections to and from a neuron is equivalent to eliminating it, an operation done previously to demonstrate the robustness of the integrator network model. Ironically, the resulting nonuniform network model, previously supposed to represent a pathological integrator, may in fact represent a healthy integrator containing neurons with realistically variable, approximately fractional-order dynamics.