时滞作用下忆阻耦合FHN-ML神经元模型的分岔分析

通过构建时滞作用下忆阻耦合FHN-ML神经元模型,研究不同时滞对该神经元系统动力学行为的影响。利用Routh-Hurwitz判据和Hopf分岔定理证明FHN-ML神经元系统平衡点的稳定性及Hopf分岔的存在性。利用范式理论和中心流形定理进一步证明FHN-ML神经元系统的分岔方向及周期解的稳定性。通过Matlab软件绘制以反转电压和电流频率为双参的周期分岔图及以电流频率为单参的峰峰间期（ISI）分岔图,发现在时滞作用下,FHN-ML神经元系统的放电模式会产生延迟现象,且当增大时滞时,延迟程度加大,混沌放电区域减小,加周期分岔的周期数减小。所得分析结果有助于理解延迟效应对电磁辐射作用下的耦合神经元网络放电活动的影响。     

海马区神经元和神经元群放电模型的研究现状

随着对大脑认知功能研究的发展，在微观一介观水平上对海马区神经元及神经元群放电及其功能的研究已成为近年来脑认知功能研究的热点。从信息学的角度，对神经元和神经元群放电进行建模与仿真是该领域研究的重要方向之一。介绍海马区单个神经元放电模型和神经元群的几类放电模型及其应用概况，并探讨各类模型的特点和面临的问题。     

神经元去极化反跳现象的研究进展

正神经元受刺激后产生动作电位,并将该刺激信号传递给其它的神经元,进而影响整个神经回路。这种接受去极化刺激后能够产生动作电位的特性,是判断细胞是否具有兴奋性的标准。然而亦有研究表明,神经元在接受超极化刺激后也能爆发动作电     

海马区神经元和神经元群放电模型的研究现状

随着对大脑认知功能研究的发展,在微观—介观水平上对海马区神经元及神经元群放电及其功能的研究已成为近年来脑认知功能研究的热点。从信息学的角度,对神经元和神经元群放电进行建模与仿真是该领域研究的重要方向之一。介绍海马区单个神经元放电模型和神经元群的几类放电模型及其应用概况,并探讨各类模型的特点和面临的问题。     

突触噪声对神经元兴奋性调节的模型研究

结合已有关于突触噪声输入下神经元放电形式现象的研究,建立一个类似生理条件下的运动神经元膜特性的数学模型。该模型再现了有无突触噪声两种情况下的神经元放电的基本形式,在含有噪声输入情况下再现了膜振荡的现象。在此基础上分别对上述两种情况神经元动作电位的个数、幅度以及阈值作了定量描述。与双斜坡刺激相比,兴奋性突触输入增加动作电位个数约为16个,但是兴奋阈值增加;抑制性突触输入减少动作电位个数约为19个,兴奋阈值减小。在抑制性噪声输入和混合突触输入的情况下,动作电位幅度增量明显比双斜坡刺激的要小,其平均值分别下降为0.68、0.33 mV。该数学模型能够很好地模拟电生理实验过程中神经元含有膜振荡的动作电位现象,这对后续电生理神经元的分析以及细胞放电的病理研究提供了手段与依据。     

哺乳动物皮层神经元模型的放电模式研究

针对一类三维哺乳动物新皮层神经元模型进行分析。该模型是结合Wilson模型和Hindmarsh-Rose模型而建立 的,得到的快变量遵守欧姆定律。快慢动力学对时间尺度相差很大的系统的分析是非常有效的,因此本研究使用快慢动 力学方法,并结合理论计算和数值模拟来探究该模型的动力学行为。首先,随着系统控制参数的改变,发现了3类簇放电 模式;然后,计算一阶Lyapunov系数,以此确定Hopf分岔是超临界或次临界的;最后,将模型与经典的Morris-Lecar模型 耦合,分析并讨论了耦合强度及外界交流刺激对耦合系统的影响。     

钠电流对皮层中间神经元放电模式影响

目的:通过分析FS模型来探索皮层抑制性中间神经元放电的规律。方法:数值分析钠离子通道参数改变的情况下,皮层中间神经元的发放模式以及不同发放模式之间的转移,并通过峰峰间距(InterSpike Intervals,ISIs)序列展示了不同发放模式转移过程中出现的各种周期分岔现象。结果与结论:随着钠通道参数的改变,出现了明显的倍周期分岔和逆倍周期分岔现象,并且最终发放模型从分岔模式回归到周期1簇的放电模式。从钠通道门变量m的三维分岔图得出,随着gd的增加,不同分岔图之间出现相似性,具有延缓特性。     

神经元后超极化电位中钙激活钾通道的介导

神经元动作电位后的超极化含有数个时相,不同时相是由不同的钙激活钾通道(Kca)来介导的.Kca包括低电导KKca(SKca)和高电导Kca(BKca).BKca的激活与动作电位的复极化有关,而SKca的激活则与后超极化(AHP)有关.按动力学和药理学标准可将AHP分为两类,研究表明,只有一类AHP与SKca的激活有关,而另一类则与一种新型的Kca有关.     

神经元后超级化电位中钙激活钾通道的介导

神经元动作电位后的超极化含有数个时相,不同时相是由不同的钙激活钾通道(Kca)来介导的.Kca包括低电导KKca(SKca)和高电导Kca(BKca).BKca的激活与动作电位的复极化有关,而SKca的激活则与后超极化(AHP)有关.按动力学和药理学标准可将AHP分为两类,研究表明,只有一类AHP与SKca的激活有关,而另一类则与一种新型的Kca有关.     

海马锥体神经元细胞外动作电位的仿真

为了从大脑神经元细胞外动作电位(EAP)记录信号中提取更多的神经元信息,本文通过建立大脑海马CA1区不同种类锥体神经元的仿真模型,研究了树突电流、细胞形态以及几种离子机制对于EAP波形的影响。结果表明:树突电流对于远离胞体处的EAP有较大的影响,对于靠近胞体的EAP作用不大;神经元形态的不同会导致EAP幅值的较大变化,但它们对于EAP波形的形状却无明显作用;钙离子电流等机制对于EAP波形的影响不明显。这些研究结果为EAP的实验记录、数据分析,以及开发利用EAP提取更多神经元信息的新方法提供了重要的依据。     

Determinants of Response Pattern of Cochlear Nucleus Neuron:a Study Based on the Model

Objective： Neurons in the cochlear nucleus show different response patterns to the short tone bursts. Because of the limitations of animal experiments, it is hard to explore the principle. Therefore, using a model to simulate CN neurons will be a feasible way. Methods： Based on the initial model mentioned in the previous study, we proposed an improved CN model in MATLAB R2012b. Results： By modifying the parameters of the model we found the interchanges among ＂primary-like＂, ＂chopper＂, and ＂onset＂ response patterns. Furthermore, we simulated the ＂pauser＂ response pattern by adding an extra input in our model. Conclusion： The results indicate that the synaptic integrations and the input modes can give rise to different characteristics of CN neurons, which eventually determine the response patterns of CN neurons.     

Oscillatory Flow in a Symmetric Bifurcation Airway Model

Flow in a symmetric bifurcation model of analytically known geometry was investigated experimentally under oscillatory flow conditions. The duration of the inspiratory and expiratory phases were set to be equal during the oscillatory period. A two velocity component laser Doppler anemometer was used to interrogate the flow field. Three different flow rates through the bifurcation were investigated. The peak Reynolds numbers, based on peak flow rates, were 700, 1278, and 2077. The Womersley number was set to 4.3 and it was kept at the same value for the three different flow rates. The results suggest that under the conditions studied a quasisteady flow assumption for oscillatory flow is valid for only about 50% of the oscillatory period, or it is limited to represent the oscillatory flow only in the vicinity of peak inspiration and peak expiration. Complex transport phenomena that occur during the transition between the respiratory phases cannot be elucidated and analyzed by quasisteady equivalents. © 1998 Biomedical Engineering Society. PAC98: 8745Hw, 8710+e, 4780+v, 4262Be, 8764-t     

Oxygen Mass Transport in a Compliant Carotid Bifurcation Model

The purpose of the present study was to investigate oxygen mass transfer in the human carotid bifurcation, focusing on the effects of the wall compliance and flow field on the temporal variation and spatial distribution of the oxygen wall flux. Details of unsteady convective-diffusive oxygen transport were examined numerically using a compliant model of the human carotid bifurcation and realistic blood flow waveforms. Results reveal that axial flow separation at the outer common-internal carotid wall can significantly alter the flow field, oxygen tension field, and oxygen wall flux distribution. At the outer wall of the sinus, the Sherwood number, Sh (non-dimensional oxygen wall flux), takes on significantly lower values than at other sites due to the attenuation of transport rates by convective flow away from wall. More specifically, the lowest value of Sh was Sh∼6 (in the sinus), which is much lower than the value of the non-dimensional oxygen consumption rate (Damkohler number, Da) in the reactive wall tissue (Da=29–39). At the inner wall of the sinus, Sh∼170 is far above the expected value of Da. This implies that flow separation on the outer wall of the sinus provides a very strong fluid mechanical barrier to oxygen transport; whereas at the inner wall of the sinus, the mechanism of transport is controlled by the wall consumption rate.     

运动神经元病患者的智能,记忆及事件相关电位研究

目的：了解运动神经元病（ＭＮＤ）患者认知障碍的特点。方法：采用韦氏成人智力量表、临床记忆量表和体感刺激诱发的事件相关脑诱发电位，对１８例ＭＮＤ患者和２４例健康人进行了测验比较。结果：ＭＮＤ患者可出现不同程度的智能、记忆障碍。其中语言智商（３３．３％）、操作智商（３８．９％）、全量表智商（２７．８％）和记忆商（３８．９％）在边界以下。本组患者表现为皮质兼皮质下智能障碍的特征。其认知电位Ｐ３００的潜伏期与对照组相比明显延长（ｐ＜０．００１），波幅明显降低（ｐ＜０．００１）。     

Bifurcation Model for Characterization of Pulmonary Architecture

A flexible mathematical model of an asymmetric bronchial airway bifurcation is presented. The bifurcation structure is automatically determined after the user specifies geometric parameters: radius of parent airway, radii of daughter airways, radii of curvature of the daughter branch toroids, bifurcation angles, and radius of curvature of carina ridge. Detailed shape in the region where the three airways merge is defined by several explicit functions and can be changed with ease in accordance with observed lung structure. These functions take into account the blunt shape of the carina, the smooth transition from the outer transition zone to the inner one, and the shift in carinal ridge starting position as a function of bifurcation asymmetry. We validated the bifurcation model by comparing it to a computed tomography image of a rat lung cast. Three‐dimensional representations of the bifurcation geometry can be viewed at http://mae.ucdavis.edu/wexler/lungs/bifurc.htm . Anat Rec, 291:379–389, 2008. © 2008 Wiley‐Liss, Inc.     

心脏记忆现象及其产生机制的研究现状

心脏记忆是近20年来才被人们开始认识的一种正常的生理现象。在未出现心力衰竭、心肌缺血等疾病,心电图未见异常的情况下,若给心脏施加易位电刺激一段时间,如心室起搏在恢复为正常窦性节律后心电图T波仍与起搏时QRS波同向及起搏停止后T波记住了起搏时QRS波形态,且这种记忆维持一段时间后才会消失。由于T波的记忆现象会影响心室复极和动作电位的不应期,有诱发或抑制心律失常发生的作用,且由它引起的T波形态的改变,与许多病理状态下,如心肌缺血时T波的形态相似,容易产生混淆等特点,使心脏记忆的研究越来越受到人们的关注。本文重点介绍了心脏记忆现象及其产生的电生理离子通道机制,并总结了当前的主要研究结果。     

Spatial Variations in Shear Stress in a 3-D Bifurcation Model at Low Reynolds Numbers

Real-time wall shear stress is difficult to monitor precisely because it varies in space and time. Microelectromechanical systems sensor provides high spatial resolution to resolve variations in shear stress in a 3-D bifurcation model for small-scaled hemodynamics. At low Reynolds numbers from 1.34 to 6.7 skin friction coefficients (C_f) varied circumferentially by a factor of two or more within the bifurcation. At a Reynolds number of 6.7, the C_f value at the lateral wall of the bifurcation along the 270^∘ plane was 7.1, corresponding to a shear stress value of 0.0061 dyn/cm². Along the 180^∘ plane, C_f was 13 or 0.0079 dyn/cm², and at the medial wall along the 90^∘ plane, C_f was 10.3 or 0.0091 dyn/cm². The experimental skin friction coefficients correlated with values derived from the Navier–Stokes solutions.     

Locomotor Responses and Neuron Excitability in Conditions of Haloperidol Blockade of Dopamine in Invertebrates and Vertebrates

Levels of movement activity were used to identify two groups of rats: those with high- and low-activity levels. Blockade of dopamine receptors with haloperidol led to suppression of locomotor activity in both groups of rats; in common snails, haloperidol decreased the rate of locomotion. The excitability of spinal centers in rats decreased 5 min after single i.v. injections, with gradual recovery seen by 30 min. Chronic administration of haloperidol suppressed post-tetanic potentiation of the H response in the gastrocnemius muscle of spinal rats. Prolonged use of haloperidol induced significant hyperpolarization of the membrane potential of command neurons in common snails and increased the action potential generation threshold. Selective pharmacological exclusion of the brain dopamine system was found to lead to decreases in the excitability of defined neurons in snails and the spinal motor centers in rats, also producing impairments in locomotor responses in these animals. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 90, No. 11, pp. 1381–1392, November, 2004.