FHN-ML电耦合神经元的发放模式和分岔分析

以FitzHugh-Nagumo(FHN)和Morris-Leca(rML)神经元模型为基础,通过两个神经元的电耦合,构建一个FHNML模型。基于FHN-ML模型,研究外界刺激和时滞对FHN-ML模型发放模式的影响,并对该模型的簇放电类型进行分类。结果表明FHN-ML模型中ML神经元发放模式对交流频率ω和钾离子平衡电位V_k改变非常敏感,可以得到不同的新型簇发放模式。随着时滞的增加,神经元放电先后经历混沌状态和周期簇放电,并且存在明显的加周期分岔现象。若应用快慢动力学分岔分析,将ML神经元中的慢变调节电流I作为分支参数,FHN-ML模型具有两种类型簇放电模式及其动力学性质。     

僧帽细胞电位发放的模型分析

本文构造从感觉神经元、僧帽细胞到大脑皮层神经元,并反馈到颗粒细胞的嗅觉神经系统模型.数值分析模型结构中各个神经元的电位发放,特别是嗅小球内的细胞电位变化,结果显示僧帽细胞的发放对感觉神经元的刺激变化较大,僧帽细胞对皮层细胞的相图出现各种模式,从而模型刻画了嗅觉系统中僧帽细胞的信息传递特性.     

一类前包钦格复合体单房室模型的动力学分析

目的:呼吸节律的产生部位和原理一直是神经生物学研究领域中的热门课题。近年来的研究表明,延髓中一个被称为前包钦格复合体(Pre-B觟tzinger complex,PBC)的区域在哺乳动物呼吸节律的产生中起着关键作用。方法:本文通过对一类前包钦格复合体神经元的单房室模型的研究,使用Matlab软件对非线性微分方程进行神经元单房室模型的构建,结合龙格库塔方法,从非线性动力学角度对模型的不同参数的一定范围的变化进行数值分析,考察其蕴含的动力学特性。结果:通过改变单房室模型的不同电生理参数,如离子平衡电位、电容、电导等,得到模型中的全发放、簇发放或者混沌状态,尤其是通过同时调整持续钠电导和依赖钙离子的内质网通道蛋白浓度,可得到明显的加周期和倍周期分岔现象。结论:结合膜电位发放图和峰峰间距图对模型的非线性动力学特性进行分析,并由模型数值分析结果探讨其信号传递和节律编码的规律,为呼吸节律的调控机制提供线索,也为进一步揭示呼吸节律的产生机理提供了重要的参考价值。     

视皮层中神经元的同步发放现象黄江涛1

在Hindmarsh-Rose(HR)单神经元模型的基础上,结合视皮层的神经网络模型,研究分析视皮层中各神经元的发放模式.数值仿真显示:视皮层网络结构的各层中,神经元的发放具有同步现象;当双极细胞的外界刺激改变时,神经元出现簇发放和峰发放两类模式;随着外界刺激强度的增强,电位发放的峰峰间距(ISI)显示分岔现象.     

视皮层中神经元的同步发放现象

在Hindmarsh—Rose（HR）单神经元模型的基础上，结合视皮层的神经网络模型，研究分析视皮层中各神经元的发放模式。数值仿真显示：视皮层网络结构的各层中，神经元的发放具有同步现象；当双极细胞的外界刺激改变时，神经元出现簇发放和峰发放两类模式；随着外界刺激强度的增强，电位发放的峰峰间距（ISI）显示分岔现象。     

一种基于最大Lyapunov指数的平衡站立能力评价方法

为了科学评价人体站立平衡能力,本文基于混沌系统非线性分析理论,提出了一种新的评价方法。该方法利用运动平台对受试者足底施加前后方向正弦式运动刺激,采用三个加速度传感器固定于受试者肩、髋、膝,采集人体平衡调节的动态数据。通过重构系统的相空间,计算得到受试者不同体段动态数据的最大Lyapunov指数(LLE),用LLE的差值平方和(SSDLLE)作为平衡能力的评价指标。最后用该方法计算了20位受试者的平衡指标,并与传统评价方法的结果进行对比,结果表明SSDLLE较为符合受试者的平衡表现,可以在一定程度上用于评测人体的平衡能力。此外,结果还表明人体各个关节的协调能力决定了平衡能力的优劣;各体段的混沌特性的差异与个体的站立平衡能力是存在相关性的。     

基于有限元分析的脊髓表面电位分布研究

有限元分析可以通过实验条件仿真研究人体及动物体器官组织中的结构、内部场强等变化情况。本文应用有限元分析软件分析与求解脊髓表面电位,研究躯体运动控制和感觉处理中诱发的脊髓中间神经元兴奋在脊髓神经中的传播特性。建立了大鼠脊髓内电信号源三维模型,利用电信号在脊髓内的传导特性,分析和计算了脊髓内部兴奋中间神经元发放出来的电信号源沿脊髓横径方向、背腹方向变化对脊髓表面电位分布的影响,得到了脊髓表面场电位分布曲线,发现脊髓表面电位分布基本呈现单调特性,且个别记录点的电位值小于附近记录点电位。     

甲壳类动物胃肠神经系统的数值分析

目的数值分析甲壳类动物胃肠神经系统神经元的电位发放。方法利用抑制神经系统的WLC(Winner less Competition)模型计算得到胃研磨和幽门神经系统的节律变化,数值说明龙虾胃研磨内的两侧牙齿和中间牙齿的运动出现切断食物、挤压食物和研磨食物的状态;结果幽门节律出现神经元AB(anterior burster)、PD(pyloric dilatator)和VD(ventricular dilator)之间的同步共振;胃研磨神经系统和幽门神经系统之间显示神经元LPG(lateral posterior gastricneuron)对神经元VD的发放传递等。结论数值结果再现了龙虾胃肠神经系统的实验现象。     

神经元功能网络的度量及性能分析

网络的度量是复杂网络理论在神经元集群信息处理机制解析中的重要研究内容之一。针对神经元功能网络的定量度量问题,系统分析了聚类系数、全局效率、特征路径长度及传递性等度量指标与网络拓扑连接变化的定量描述关系。基于锋电位发放序列构建了神经元功能网络,仿真研究表明,构建的网络可以有效表征神经元之间的连接关系。利用鸽子弓状皮质尾外侧区(NCL)实测数据,研究了神经元功能网络对鸽子运动行为的编码特性。研究表明,NCL区神经元功能网络可以有效编码鸽子的运动行为,而且四种度量指标在鸽子左转、直行和右转等不同行为时具有显著差异。研究结果表明本文的神经元功能网络构建方法可行,对于解析大脑神经信息处理机制具有较高的应用价值。     

BKCa通道对小鼠杏仁核锥体神经元兴奋性的影响

目的:观察大电导钙依赖性钾通道(large conductance calcium-activated potassium channels,BKCa)对小鼠外侧杏仁核锥体细胞神经元兴奋性的影响。方法:采用全细胞脑片膜片钳技术,记录小鼠杏仁核锥体神经元动作电位频率和幅度的变化。结果:在电流钳全细胞记录模式下输入一定强度的正电流诱导神经元发放动作电位,观察到灌流BKCa通道阻断剂iberiotoxin(IBTX100nmol/L)可显著增加动作电位发放频率,并缩短首个动作电位出现潜伏期;相反,BKCa通道激动剂NS1619(10μmol/L)可显著降低动作电位发放频率,并延长首个动作电位出现潜伏期。此外,BKCa通道参与单个动作电位后超极化电位(after hyperpolarizing potential,AHP)的形成。在电极内液中加入快速型钙离子螯合剂BAPTA(10mmol/L)可取消IBTX和NS1619对动作电位的影响。结论:BKCa通道对杏仁核锥体神经元的兴奋性具有重要的调节作用。     

Dual sensory-motor function for a molluskan statocyst network

In mollusks, statocyst receptor cells (SRCs) interact with each other forming a neural network; their activity is determined by both the animal's orientation in the gravitational field and multimodal inputs. These two facts suggest that the function of the statocysts is not limited to sensing the animal's orientation. We studied the role of the statocysts in the organization of search motion during hunting behavior in the marine mollusk, Clione limacina. When hunting, Clione swims along a complex trajectory including numerous twists and turns confined within a definite space. Search-like behavior could be evoked pharmacologically by physostigmine; application of physostigmine to the isolated CNS produced "fictive search behavior" monitored by recordings from wing and tail nerves. Both in behavioral and in vitro experiments, we found that the statocysts are necessary for search behavior. The motor program typical of searching could not be produced after removing the statocysts. Simultaneous recordings from single SRCs and motor nerves showed that there was a correlation between the SRCs activity and search episodes. This correlation occurred even though the preparation was fixed and, therefore the sensory stimulus was constant. The excitation of individual SRCs could in some cases precede the beginning of search episodes. A biologically based model showed that, theoretically, the hunting search motor program could be generated by the statocyst receptor network due to its intrinsic dynamics. The results presented support for the idea that the statocysts are actively involved in the production of the motor program underlying search movements during hunting behavior.     

Neuronal mechanisms for the control of body orientation in clione II. Modifications in the activity of postural control system

The marine mollusk Clione limacina, when swimming, can stabilize different body orientations in the gravitational field. The stabilization is based on the reflexes initiated by activation of the statocyst receptor cells and mediated by the cerebro-pedal interneurons that produce excitation of the motoneurons of the effector organs; tail and wings. Here we describe changes in the reflex pathways underlying different modes of postural activity; the maintenance of the head-up orientation at low temperature, the maintenance of the head-down orientation at higher temperature, and a complete inactivation of the postural mechanisms during defense reaction. Experiments were performed on the CNS-statocyst preparation. Spike discharges in the axons of different types of neurons were recorded extracellularly while the preparation was rotated in space through 360 degrees in different planes. We characterized the spatial zones of activity of the tail and wing motoneurons and the CPB3 interneurons mediating the effects of statocyst receptor cells on the tail motoneurons. This was done at different temperatures (10 and 20 degrees C). The "fictive" defense reaction was evoked by electrical stimulation of the head nerve. At 10 degrees C, a tilt of the preparation evoked activation in the tail motoneurons and wing retractor motoneurons contralateral to the tilt and in the wing locomotor motoneurons ipsilateral to the tilt. At 20 degrees C, the responses in the tail motoneurons and in the wing retractor motoneurons occurred reversed; these neurons were now activated with the ipsilateral tilt. In the wing locomotor motoneurons the responses at 20 degrees C were suppressed. During the defense reaction, gravitational responses in all neuron types were suppressed. Changes in the chains of tail reflexes most likely occurred at the level of connections from the statocyst receptor cells to the CPB3 interneurons. The changes in gravitational reflexes revealed in the present study are sufficient to explain the corresponding modifications of the postural behavior in Clione.     

Asymmetrical effect of GABA on the postural orientation in Clione

The marine mollusk Clione limacina, when swimming, normally stabilizes the vertical body orientation by means of the gravitational tail reflexes. Horizontal swimming or swimming along inclined ascending trajectories is observed rarely. Here we report that GABA injection into intact Clione resulted in a change of the stabilized orientation and swimming with a tilt of approximately 45 degrees to the left. The analysis of modifications in the postural network underlying this effect was done with in vitro experiments. The CNS was isolated together with the statocysts. Spike discharges in the axons of two groups of motoneurons responsible for the left and right tail flexion, as well as in the axons of CPB3 interneurons mediating signals from the statocyst receptors to the motoneurons, were recorded extracellularly when the preparation was rotated in space. Normally the tail motoneurons of the left and right groups were activated with the contralateral tilt of the preparation. Under the effect of GABA, the gravitational responses in the right group of motoneurons and in the corresponding interneurons were dramatically reduced while the responses in the left group remained unchanged. The most likely site of the inhibitory GABA action is the interneurons mediating signals from the statocysts to the right group of tail motoneurons. The GABA-induced asymmetry of the left and right gravitational tail reflexes, observed in the in vitro experiments, is consistent with a change of the stabilized orientation caused by GABA in the intact Clione.     

Statocyst hair cell activation of identified interneurons and foot contraction motor neurons in Hermissenda

Pavlovian conditioning of Hermissenda produces both light-elicited inhibition of normal positive phototactic behavior and conditioned stimulus (CS)-elicited foot-shortening. Rotation, the unconditioned stimulus (US) elicits foot-shortening and reduced forward ciliary locomotion. The neural circuit supporting ciliary locomotion and its modulation by light is known in some detail. However, the neural circuits responsible for rotation-elicited foot-shortening and reduced forward ciliary locomotion are not known. Here we describe components of the neural circuit in Hermissenda that produce anterior foot contraction and ciliary activation mediated by statocyst hair cells. We have characterized in semi-intact preparations newly identified pedal ventral contraction motor neurons (VCMNs) and interneurons (I(b)). Type I(b) interneurons receive polysynaptic input from statocyst hair cells and project directly to VCMNs and cilia-activating motor neurons. Depolarization of VCMNs with extrinsic current in normal artificial seawater (ASW) and high-divalent cation ASW, and under conditions where central synaptic transmission was suppressed with 5 mM Ni(2+) ASW, elicited a contraction of the ipsilateral anterior foot measured from videotape recordings. Mechanical displacement of the statocyst or depolarization of identified statocyst hair cells with extrinsic current elicited spikes and complex excitatory postsynaptic potentials (EPSPs) in type I(b) interneurons and complex EPSPs and spikes recorded in VCMNs. Type I(b) interneurons are electrically coupled and project to VCMNs and VP1 cilia-activating motor neurons located in the contralateral pedal ganglia. The results indicate that statocyst hair-cell-mediated anterior foot contraction and graviceptive ciliary locomotion involve different interneuronal circuit components from the circuit previously identified as supporting light modulated ciliary locomotion.     

Sensory regulation of network components underlying ciliary locomotion in Hermissenda

Ciliary locomotion in the nudibranch mollusk Hermissenda is modulated by the visual and graviceptive systems. Components of the neural network mediating ciliary locomotion have been identified including aggregates of polysensory interneurons that receive monosynaptic input from identified photoreceptors and efferent neurons that activate cilia. Illumination produces an inhibition of type I(i) (off-cell) spike activity, excitation of type I(e) (on-cell) spike activity, decreased spike activity in type III(i) inhibitory interneurons, and increased spike activity of ciliary efferent neurons. Here we show that pairs of type I(i) interneurons and pairs of type I(e) interneurons are electrically coupled. Neither electrical coupling or synaptic connections were observed between I(e) and I(i) interneurons. Coupling is effective in synchronizing dark-adapted spontaneous firing between pairs of I(e) and pairs of I(i) interneurons. Out-of-phase burst activity, occasionally observed in dark-adapted and light-adapted pairs of I(e) and I(i) interneurons, suggests that they receive synaptic input from a common presynaptic source or sources. Rhythmic activity is typically not a characteristic of dark-adapted, light-adapted, or light-evoked firing of type I interneurons. However, burst activity in I(e) and I(i) interneurons may be elicited by electrical stimulation of pedal nerves or generated at the offset of light. Our results indicate that type I interneurons can support the generation of both rhythmic activity and changes in tonic firing depending on sensory input. This suggests that the neural network supporting ciliary locomotion may be multifunctional. However, consistent with the nonmuscular and nonrhythmic characteristics of visually modulated ciliary locomotion, type I interneurons exhibit changes in tonic activity evoked by illumination.     

Serotonin-induced spike narrowing in a locomotor pattern generator permits increases in cycle frequency during accelerations

During serotonin-induced swim acceleration in the pteropod mollusk Clione limacina, interneurons of the central pattern generator (CPG) exhibit significant action potential narrowing. Spike narrowing is apparently necessary for increases in cycle frequency during swim acceleration because, in the absence of narrowing, the combined duration of the spike and the inhibitory postsynaptic potential (IPSP) of a single cycle is greater than the available cycle duration. Spike narrowing could negatively influence synaptic efficacy in all interneuron connections, including reciprocal inhibitory connections between the two groups of antagonistic CPG interneurons as well as the interneuron-to-motoneuron connections. Thus compensatory mechanisms must exist to produce the overall excitatory behavioral change of swim acceleration. Such mechanisms include 1) a baseline depolarization of interneurons, which brings them closer to spike threshold, 2) enhancement of their postinhibitory rebound, and 3) direct modulation of swim motoneurons and muscles, all through inputs from serotonergic modulatory neurons.     

Neural mechanisms underlying co-activation of functionally antagonistic motoneurons during a Clione feeding behavior

The ability of some neural networks to produce multiple motor patterns required during different behaviors is a well-documented phenomenon. We describe here a dramatic transition from coordinated inhibition between two functionally antagonistic groups of motoneurons to their co-activation in the feeding neural network of the predatory mollusk Clione limacina. To seize its prey, Clione uses specialized oral appendages, called buccal cones, which are controlled by two groups of motoneurons: cerebral A (Cr-A) neurons controlling buccal cone protraction and cerebral B (Cr-B) neurons controlling buccal cone retraction. When Cr-A neurons are active, Cr-B neurons usually receive strong inhibitory inputs that terminate their firing, which leads to the full protraction and elongation of the buccal cones. We have found, however, that the Cr-A and Cr-B motoneurons sometimes burst simultaneously without any traces of inhibition in the Cr-B motoneurons. This transformation of the neural network activity from inhibitory interactions to co-activation presumably occurs during the late "extraction" period of the feeding behavior when buccal cones become partially retracted and rhythmically active. The transition from the inhibitory interaction to co-activation is controlled by the activity of a single pair of cerebral interneurons (Cr-Aint interneurons), which are electrically coupled to the Cr-A neurons and monosynaptically inhibit Cr-B neurons. Normally, the Cr-Aint interneurons are active along with Cr-A motoneurons and inhibit Cr-B motoneurons. During a period of co-activation, however, these interneurons do not produce spikes, thus allowing Cr-A motoneuron activation without inhibition of the Cr-B motoneurons.     

Neuronal mechanisms for the control of body orientation in Clione I. Spatial zones of activity of different neuron groups.

The marine mollusk Clione limacina, when swimming, can stabilize different body orientations in the gravitational field. Here we describe one of the modes of operation of the postural network in Clione-maintenance of the vertical, head-up orientation. Experiments were performed on the CNS-statocyst preparation. Spike discharges in the axons of different types of neurons were recorded extracellularly when the preparation was rotated in space through 360 degrees in different planes. We characterized the spatial zones of activity of the tail and wing motor neurons as well as of the CPB3 interneurons mediating the effects of statocyst receptor cells on the tail motor neurons. It was found that the activity of the tail motor neurons increased with deviation of the preparation from the normal, rostral-side-up orientation. Their zones of activity were very wide ( approximately 180 degrees ). According to the zone position, three distinct groups of tail motor neuron (T1-T3) could be distinguished. The T1 group had a center of the zone near the ventral-side-up orientation, whereas the zones of T2 and T3 had their centers near the left-side-up and the right-side-up positions, respectively. By comparing the zone of activity with the direction of tail bending elicited by each of the groups, one can conclude that gravitational reflexes mediated by the T1, T2, and T3 groups will evoke turning of the animal toward the head-up orientation. Two identified wing motor neurons, 1A and 2A, causing the wing beating, were involved in gravitational reactions. They were activated with the downward inclination of the ipsilateral side. Opposite reactions were observed in the motor neurons responsible for the wing retraction. A presumed motor effect of these reactions is an increase of oscillations in the wing that is directed downward and turning of Clione toward the head-up orientation. Among the CPB3 interneurons, at least four groups could be distinguished. In three of them (IN1, IN2, and IN3), the zones of activity were similar to those of the three groups (T1, T2, and T3) of the tail motor neurons. The group IN4 had the center of its zone in the dorsal-side-up position; a corresponding group was not found among the tail motor neurons. In lesion experiments, it was found that gravitational input mediated by a single CPB3 interneuron produced activation of its target tail motor neurons in their normal zones, but the strength of response was reduced considerably. This finding suggests that several interneurons with similar spatial zones converge on individual tail motor neurons. In conclusion, because of a novel method, activity of the neuronal network responsible for the postural control in Clione was characterized in the terms of gravitational responses in different neuron groups comprising the network.     

Coordinated excitatory effect of GABAergic interneurons on three feeding motor programs in the mollusk Clione limacina

Coordination between different motor centers is essential for the orderly production of all complex behaviors. Understanding the mechanisms of such coordination during feeding behavior in the carnivorous mollusk Clione limacina is the main goal of the current study. A bilaterally symmetrical interneuron identified in the cerebral ganglia and designated Cr-BM neuron produced coordinated activation of neural networks controlling three main feeding structures: prey capture appendages called buccal cones, chitinous hooks used for prey extraction from the shell, and the toothed radula. The Cr-BM neuron produced strong excitatory inputs to motoneurons controlling buccal cone protraction. It also induced a prominent activation of the neural networks controlling radula and hook rhythmic movements. In addition to the overall activation, Cr-BM neuron synaptic inputs to individual motoneurons coordinated their activity in a phase-dependent manner. The Cr-BM neuron produced depolarizing inputs to the radula protractor and hook retractor motoneurons, which are active in one phase, and hyperpolarizing inputs to the radula retractor and hook protractor motoneurons, which are active in the opposite phase. The Cr-BM neuron used GABA as its neurotransmitter. It was found to be GABA-immunoreactive in the double-labeling experiments. Exogenous GABA mimicked the effects produced by Cr-BM neuron on the postsynaptic neurons. The GABA antagonists bicuculline and picrotoxin blocked Cr-BM neuron-induced PSPs. The prominent coordinating effect produced by the Cr-BM neuron on the neural networks controlling three major elements of the feeding behavior in Clione suggests that this interneuron is an important part of the higher-order system for the feeding behavior.     

The eyeless mutant Mexican salamander (Ambystoma mexicanum): evidence for an imbalanced anteroposterior morphogenetic system

Prospective anterolateral neural fold was grafted from normal axolotls into the posterior neural fold region (statocyst area) of eyeless mutant hosts. These unilateral anteroposterior grafts stimulated bilateral eye formation in the eyeless mutant at a rate of 79%. Replacing the statocyst area of mutants with the statocyst area from normals stimulated bilateral eye formation in 49% of the cases. Grafting of prospective anterolateral neural fold between normals and mutants or excising the statocyst region of mutants, had no effect. The results are interpreted on the basis of a hypothetical anteroposterior morphogenetic system that might be out of balance in the mutant.