Adaptation to visual stimulation modifies the burst firing property of V1 neurons

The mean firing rate of visual cortical neurons is reduced after prolonged visual stimulation, but the underlying process by which this occurs as well as the biological significance of this phenomenon remains unknown. Computational neuroscience studies indicate that high-frequency bursts in stimulus-driven responses can be transmitted across synapses more reliably than isolated spikes, and thus may carry accurate stimulus-related information. Our research examined whether or not adaptation affects the burst firing property of visual cortical neurons by examining changes in the burst firing changes of V1 neurons during adaptation to the preferred visual stimulus. The results show that adaptation to prolonged visual stimulation significantly decreased burst frequency (bursts/s) and burst length (spikes/burst), but increased burst duration and the interspike interval within bursts. These results suggest that the adaptation of V1 neurons to visual stimulation may result in a decrease of feedforward response gain but an increase of functional activities from lateral and/or feedback connections, which could lead to a reduction in the effectiveness of adapted neurons in transmitting information to its driven neurons.     

Dynamic excitation states and firing patterns are controlled by sodium channel kinetics in myenteric neurons: a simulation study

Enteric neurons located in the gastro-intestinal tract are of particular importance to control digestive functions such as motility and secretion. In our recent publication, we showed that mouse myenteric neurons exhibit 2 types of tetrodotoxin-resistant Na⁺ currents: a fast inactivating Na⁺ current produced by Nav1.5 channels, present in nearly all myenteric neurons, and a persistent Na⁺ current attributed to Nav1.9 channels, restricted to the intrinsic primary afferent neurons (IPANs). By combination of experimental recording and computer simulation we found that Nav1.5 contributed to the upstroke velocity of action potentials (APs), whereas Nav1.9 opposed AP repolarization. Here, we detailed the Na⁺, Ca²⁺ and K⁺ currents used in our computational model of IPAN. We refined the prototype cell to reproduce the sustained firing pattern recorded in situ. As shown in experimental conditions we demonstrated that Nav1.9 channels critically determine the up-state life-time and thus, are essential to sustain tonic firing.     

睡眠稳态的电生理机制

大脑需要稳态系统来维持神经元的正常活动。睡眠不足会影响到有机体的生理功能,因此清醒时不断累积的睡眠压力会迫使哺乳动物进入睡眠状态,长时间清醒（睡眠剥夺）则会延长或加深随后的睡眠,这一现象被称为睡眠稳态（sleep homeostasis）。探明睡眠稳态的电生理机制有利于改善睡眠,治疗相关疾病,但目前仍存在许多问题。鉴于此,本文围绕睡眠稳态的电生理机制,首先关注睡眠稳态公认的电生理标志物——慢波活动,接下来介绍神经元放电率的相关研究,最后从脑区差异、睡眠阶段、学习记忆和物种差异几个方面进行展望。     

神经递质释放机制的实验研究-即发态突触小泡假说

突触小泡（ＳｙｎａｐｔｉｃＶｅｓｉｃｌｅ）在神经递质释放过程中起关键性作用。采用膜片钳技术对突触前后细胞同步钳位研究了爪蟾胚胎神经元突触递质释放的过程,提出了如下小泡释放的假说：锚定在突触前膜的小泡中包含两类小泡：锚定态小泡和即发态小泡（即发态小泡定义为钙离子依赖性即时释放的小泡）。后者在动作电位到达时立即释放,而处于锚定态的小泡只有转换为钙离子依赖性释放的即发态时才能进入递质释放程序     

Estimation of population firing rates and current source densities from laminar electrode recordings

This model study investigates the validity of methods used to interpret linear (laminar) multielectrode recordings. In computer experiments extracellular potentials from a synaptically activated population of about 1,000 pyramidal neurons are calculated using biologically realistic compartmental neuron models combined with electrostatic forward modeling. The somas of the pyramidal neurons are located in a 0.4 mm high and wide columnar cylinder, mimicking a stimulus-evoked layer-5 population in a neocortical column. Current-source density (CSD) analysis of the low-frequency part (<500 Hz) of the calculated potentials (local field potentials, LFP) based on the ‘inverse’ CSD method is, in contrast to the ‘standard’ CSD method, seen to give excellent estimates of the true underlying CSD. The high-frequency part (>750 Hz) of the potentials (multi-unit activity, MUA) is found to scale approximately as the population firing rate to the power 3/4 and to give excellent estimates of the underlying population firing rate for trial-averaged data. The MUA signal is found to decay much more sharply outside the columnar populations than the LFP.     

NeuroXidence: reliable and efficient analysis of an excess or deficiency of joint-spike events

We present a non-parametric and computationally efficient method named NeuroXidence that detects coordinated firing of two or more neurons and tests whether the observed level of coordinated firing is significantly different from that expected by chance. The method considers the full auto-structure of the data, including the changes in the rate responses and the history dependencies in the spiking activity. Also, the method accounts for trial-by-trial variability in the dataset, such as the variability of the rate responses and their latencies. NeuroXidence can be applied to short data windows lasting only tens of milliseconds, which enables the tracking of transient neuronal states correlated to information processing. We demonstrate, on both simulated data and single-unit activity recorded in cat visual cortex, that NeuroXidence discriminates reliably between significant and spurious events that occur by chance.     

混沌放电的可兴奋性细胞对外界刺激反应敏感的动力学机制

在大鼠损伤背根节神经元受到去甲肾上腺(NE)、四乙基胺(TEA)和高浓度钙等剌激的实验中,观察到非周期放电的神经元明显地比周期放电的神经元对外界刺激的反应敏感程度高。现有的结果表明许多非周期放电的神经元实际上表现为确定性的混沌运动,比如混沌尖峰放电、混沌簇放电以及整数倍放电等。以修正的胰腺B细胞Chay模型为例,通过对其分岔结构的分析和对构成混沌吸引子的基本骨架的不稳定周期轨道的计算,揭示了分岔、激变和混沌运动对参数敏感依赖性是该现象产生的动力学机制。同时指出以往使用平均发放率来刻划可兴奋性细胞放电活动存在的缺陷,提出了一种新的利用周期轨道信息的刻划方法。     

基于生理生态过程的大麦顶端发育和物候期模拟模型检验

为测试研究I 模型BarleyGrow,采用4个生态区(南京、扬州、武汉、昆明)、10个大麦品种在不同播期下的顶端发育和物候期资料,对BarleyGrow、YDmodel和SUCROS模型进行对比检验和评价.利用遗传-模拟退火算法确定各品种的遗传参数,提高了应用程序求算参数的精度.从模型的整体预测效果来看,BarleyGrow对不同地区、不同播期、不同品种的各顶端发育和物候期预测准确而稳定,均方差RMSE在1.06～7.94d之间,而YDmodel为6.26～13.35d,SUCROS为11.22～20.28d.各参试品种对BarleyGrow中灌浆期基点温度、生理春化时间、临界日长、最短苗穗期4参数反应敏感.经改进的生理发育时间(PDT)模拟模型(BarleyGrow)对中国广大地区不同温光条件下的大麦顶端发育和物候发育均具有较好的预测效果,尤其对药隔期、二裂期、毛状期、抽穗期、灌浆期、成熟期的模拟精度高而稳定,表现出较强的机理性以及较好的预测性.     

高频刺激丘脑底核对帕金森病大鼠模型纹状体神经元放电的影响

目的:观察高频刺激丘脑底核(STN)对帕金森病(PD)大鼠模型纹状体 (STR)神经元自发放电的影响.方法:应用6-羟基多巴胺(6-OHDA)制备偏侧PD大鼠模型,丘脑底核区插入刺激电极进行高频刺激,采用细胞外单位记录的方法观察STR神经元自发放电频率的改变.结果:正常大鼠刺激后STR神经元反应主要以兴奋型反应为主, PD大鼠STR神经元反应主要以兴奋抑制型为主,且随着刺激时间的延长,抑制持续时间逐渐增加,持续时间与刺激时间密切相关(r=0.94).结论:刺激STN可使PD大鼠纹状体的异常放电得到改善,提示高频电刺激STN可作为一种有效的治疗PD的方法.     

神经节细胞群体同步放电模式编码的感受野特性

应用多电极同步记录技术,对牛蛙视网膜神经节细胞在伪随机棋盘格刺激下的放电活动进行胞外记录。依据记录到的神经节细胞放电情况,利用一种数据压缩算法,通过最大化压缩放电序列的信息熵,对多个神经节细胞进行群体划分,得到同步放电神经节细胞群体。利用基于动作电位的刺激平均法(spike triggered average,STA),分别计算出每个同步放电神经节细胞群体内单个神经节细胞放电活动所编码的感受野(单细胞感受野),以及群体内所有神经节细胞同步放电活动所编码的感受野(群体感受野)。计算结果显示,对于所有神经节细胞群体,约80%神经节细胞群体的群体感受野面积小于群体内所有单细胞感受野面积的平均值,约60%神经节细胞群体的群体感受野面积小于群体内任意单细胞感受野面积。在棋盘格刺激下,神经节细胞放电活动会发生对比度适应。进一步以群体感受野面积小于群体内任意单细胞感受野面积的神经节细胞群体为研究对象,考察群体感受野在对比度适应过程中的动态变化,结果显示,85%神经节细胞群体的群体感受野面积在适应后期变小。