Slow Gamma Activity of Local Field Potentials (LFP) in the Freely Moving Rat Relates to Movement

Quantitative assessment of local field potentials by means of Fast Fourier Transformation (FFT) results in the so-called power density spectrum. Within this spectrum particular frequency ranges are defined in order to relate these to behavior. Frequencies above 35 Hz are generally labeled as gamma oscillations, especially as low gamma (40 - 55 Hz) or high gamma (70 - 100 Hz). In order to learn more about this feature, we implanted a set of 4 bipolar concentric steel electrodes in frontal cortex, hippocampus, striatum and midbrain reticular formation of 10 rats. After recovery, field potentials were recorded and wirelessly transmitted to our computer for frequency analysis. At the same time, motion was registered during the whole experimental period of 5.75 hours. Results revealed that low gamma activity only emerged when the animal moved—at least his head. FFT of the data showed—besides other frequencies—a slow gamma activity peaking around 47 Hz pre-dominantly within the striatum, less in frontal cortex and reticular formation and nearly none in the hippocampus. Spectral analysis was performed for single epochs of 4 seconds and all 15 minutes intervals. Correlation analysis of these intervals was done to motion data. All rats showed a highly significant correlation between gamma activity and movement. We therefore conclude from these experiments that this slow gamma activity of the field potentials is not only related to movement, but possibly part of the general neuronal coding of movement.

LSDA-APF:A Local Obstacle Avoidance Algorithm for Unmanned Surface Vehicles Based on 5G Communication Environment

In view of the complex marine environment of navigation,especially in the case of multiple static and dynamic obstacles,the traditional obstacle avoidance algorithms applied to unmanned surface vehicles(USV)are prone to fall into the trap of local optimization.Therefore,this paper proposes an improved artificial potential field(APF)algorithm,which uses 5G communication technology to communicate between the USV and the control center.The algorithm introduces the USV discrimination mechanism to avoid the USV falling into local optimization when the USV encounter different obstacles in different scenarios.Considering the various scenarios between the USV and other dynamic obstacles such as vessels in the process of performing tasks,the algorithm introduces the concept of dynamic artificial potential field.For the multiple obstacles encountered in the process of USV sailing,based on the International Regulations for Preventing Collisions at Sea(COLREGS),the USV determines whether the next step will fall into local optimization through the discriminationmechanism.The local potential field of the USV will dynamically adjust,and the reverse virtual gravitational potential field will be added to prevent it from falling into the local optimization and avoid collisions.The objective function and cost function are designed at the same time,so that the USV can smoothly switch between the global path and the local obstacle avoidance.The simulation results show that the improved APF algorithm proposed in this paper can successfully avoid various obstacles in the complex marine environment,and take navigation time and economic cost into account.

Mechanistic roles of the subthalamic nucleus and internal globus pallidus:evidence from local field potentials and deep brain stimulation

Deep brain stimulation (DBS) has become an effective therapeutic option for neurological and psychiatric disorders such as Parkinson’s disease (PD), dystonia, and obsessive-compulsive disorder. The subthalamic nucleus (STN) and internal globus pallidus (GPi) are by far the most commonly used targets for DBS in the treatment of PD. However, STN/GPi stimulation sometimes causes side effects, including motor fluctuations, cognitive declines, and worse emotional experience, which affect patients’ postoperative quality of life. Recent invasive electrophysiological studies are driven by the desire to better understand the mechanisms of therapeutic actions and side effects of STN/GPi stimulation. These studies investigated the function of the STN and GPi in motor, cognitive and affective processes by recording single- neuron firing patterns during the surgery or local field potentials after the surgery. Here we review the relevant studies to provide an integrative picture of the functional roles of the STN and GPi within the basal ganglia loops for motor, cognition, and emotion. Previous studies suggested that STN and GPi gamma oscillations encode the strength and speed of voluntary movements (execution), whereas beta oscillations reflect the effort and demand of potential movements (preparation). In the cognitive domain, oscillatory beta activity in the STN is involved when people have to stop an inappropriate action or to suppress salient but task-irrelevant information, whereas theta/delta activity is associated with the adjustment of decision thresholds and cost-benefit trade-off. In the affective domain, STN activity in the alpha band may represent the valence and arousal of emotional information.

Local field potentials,spiking activity,and receptive fields in human visual cortex

The concept of receptive field(RF) is central to sensory neuroscience. Neuronal RF properties have been substantially studied in animals,while those in humans remain nearly unexplored. Here, we measured neuronal RFs with intracranial local field potentials(LFPs) and spiking activity in human visual cortex(V1/V2/V3). We recorded LFPs via macro-contacts and discovered that RF sizes estimated from lowfrequency activity(LFA, 0.5–30 Hz) were larger than those estimated from low-gamma activity(LGA, 30–60 Hz) and high-gamma activity(HGA, 60–150 Hz). We then took a rare opportunity to record LFPs and spiking activity via microwires in V1 simultaneously. We found that RF sizes and temporal profiles measured from LGA and HGA closely matched those from spiking activity. In sum, this study reveals that spiking activity of neurons in human visual cortex could be well approximated by LGA and HGA in RF estimation and temporal profile measurement, implying the pivotal functions of LGA and HGA in early visual information processing.

Hippocampal ischemia causes deficits in local field potential and synaptic plasticity

The long-term enhancement in glutamate receptor mediated excitatory responses has been observed in stroke model. This pathological form of plasticity, termed post-ischemic long-term potentiation （i-LTP）, points to functional reorganization after stroke. Little is known, however, about whether and how this i-LTP would affect subsequent induction of synaptic plasticity. Here, we first directly confirmed that i-LTP was induced in the endothelin-l-induced ischemia model as in other in vitro models. We also demonstrated increased expression of NR2B, CaMKII and p-CaMKII, which are reminiscent of i-LTP. We further induced LTP of field excitatory post- synaptic potentials （fEPSPs） on CA1 hippocampal neurons in peri-infarct regions of the endothelin-l-induced mini-stroke model. We found that LTP of fEPSPs, induced by high-frequency stimulation, displayed a progressive impairment at 12 and 24 hours after ischemia. Moreover, using in vivo multi-channel recording, we found that the local field potential, which represents electrical property of cell ensembles in more restricted regions, was also dam- pened at these two time points. These results suggest that i-LTP elevates the induction threshold of subsequent synap- tic plasticity. Our data helps to deepen the knowledge of meta-synaptic regulation of plasticity after focal ischemia.

The role of local field potential coupling in epileptic synchronization

This review hopes to clearly explain the following viewpoints： （1） Neuronal synchronization underlies brain functioning, and it seems possible that blocking excessive synchronization in an epileptic neural network could reduce or even control seizures. （2） Local field potential coupling is a very common phenomenon during synchronization in networks. Removal of neurons or neuronal networks that are coupled can significantly alter the extracellular field potential. Interventions of coupling mediated by local field potentials could result in desynchronization of epileptic seizures. （3） The synchronized electrical activity generated by neurons is sensitive to changes in the size of the extracellular space, which affects the efficiency of field potential transmission and the threshold of cell excitability. （4） Manipulations of the field potential fluctuations could help block synchronization at seizure onset.

Local minima-free design of artificial coordinating fields

In order to overcome the drawbacks of conventional artificial potential fields (APF) based methods for the motion planning problems of mobile robots in dynamic uncertain environments, an artificial coordinating fields (ACF) based method has been proposed recently. This paper deals with the reachability problem of the ACF, that is, how to design and choose the parameters of the ACF and how the environment should be such that the robot can reach its goal without being trapped in local minima. Some sufficient conditions for these purposes are developed theoretically. Theoretical analyses show that, the ACF can effectively remove local minima in dynamic uncertain environments with V-shape or U-shape obstacles, and guide the mobile robot to reach its goal with some necessary environment constraints and based on the methods provided in this paper to properly choose the parameters of the ACF. Comparisons between the ACF and APF, and simulations are provided to illustrate the advantages of the ACF.

Virtual local target method for avoiding local minimum in potential field based robot navigation

A novel robot navigation algorithm with global path generation capability is presented. Local minimum is a most intractable but is an encountered frequently problem in potential field based robot navigation.Through appointing appropriately some virtual local targets on the journey, it can be solved effectively. The key concept employed in this algorithm are the rules that govern when and how to appoint these virtual local targets. When the robot finds itself in danger of local minimum, a virtual local target is appointed to replace the global goal temporarily according to the rules. After the virtual target is reached, the robot continues on its journey by heading towards the global goal. The algorithm prevents the robot from running into local minima anymore. Simulation results showed that it is very effective in complex obstacle environments.

Effect of propofol on local field potential in rat prefrontal cortex during working memory task

Propofol may produce memory impairment during anesthesia procedure. Local field potentials (LFPs) are used with increasing frequency in recent years to link neural activity to perception and cognition. In this study, effect of propofol on LFPs in rat’s prefrontal cortex during working memory task was evaluated. Young (approximately 3 month) male Sprague-Dawley rats were divided into two group: propofol rats and control rats. Propofol rats received propofol at 0.9 mg/Kg·min intravenously for 2 h. After 12 h, LFPs of all rats were measured simultaneously from multiple electrodes placed in prefrontal cortex while rats were performing a working memory task in Y-maze. LFPs instantaneous phase were obtained by applying Hilbert transform, and cross-correlation coherence of LFPs was calculated. The results indicate that propofol decreased the correct rate and crosscorrelation coherence of LFPs on the first two days (p 0.05). Our results suggest that propofol can impair cross-correlation coherence of LFPs in the first two days, but not long time.

Effect of focused ultrasound stimulation at different ultrasonic power levels on the local field potential power spectrum

Local field potential(LFP) signals of the rat hippocampus were recorded under noninvasive focused ultrasound stimulation(FUS) with different ultrasonic powers. The LFP mean absolute power was calculated with the Welch algorithm at the delta, theta, alpha, beta, and gamma frequency bands. The experimental results demonstrate that the LFP mean absolute power at different frequency bands increases as the ultrasound power increases.

经颅磁声电刺激对健康与帕金森病大鼠神经回路中beta振荡的影响

背景:经颅磁声电刺激是一种基于磁声耦合电效应的无创、高精度脑神经聚焦刺激方法,可调节神经节律振荡活动,从而影响大脑的运动、认知等功能。目的:探究经颅磁声电刺激对健康与帕金森病大鼠神经回路中beta振荡的影响。方法:①动物实验:采用随机数字表法将24只Wistar大鼠随机分为4组,每组6只:正常对照组不进行任何干预;正常刺激组大脑前额叶皮质接受经颅磁声电刺激(空间峰值脉冲平均强度为13.33 W/cm^(2),基波频率为0.4 MHz,基波周期数为1000,脉冲重复频率为200 Hz);模型对照组、模型刺激组通过腹腔注射1-甲基-4-苯基-1,2,3,6-四氢吡啶建立帕金森病模型,造模成功后,模型对照组大脑前额叶皮质接受经颅磁声电假刺激,模型刺激组大脑前额叶皮质接受经颅磁声电刺激,每天刺激时长2.0 min,刺激结束停留8-10 min后,采集大鼠执行T迷宫过程中局部场电位信号并同时记录行为学正确率,对比分析各组局部场电位信号能量的时频分布情况和行为差异,当大鼠正确率连续3 d高于80%后停止刺激实验和T迷宫实验。②建模仿真实验:构建经颅磁声电刺激下皮质-基底神经节回路模型,分别改变超声发射周期(5,10,20 ms)、超声发射占空比(30%,50%,90%)和感应电流密度(20,50,100μA/cm^(2)),比较不同刺激参数下健康与帕金森病大鼠beta振荡的功率谱密度值。结果与结论:①动物实验:正常对照组大鼠的空间学习能力强于模型对照组(P<0.001),正常刺激组大鼠的空间学习能力强于正常对照组(P<0.05),模型刺激组大鼠的空间学习能力强于模型对照组(P<0.01);正常对照组beta振荡能量分布较为集中,正常刺激组较正常对照组beta振荡信号能量有所降低,模型对照组与模型刺激组beta振荡能量广泛分布且能量值显著高于正常对照组、正常刺激组,并且模型刺激组beta振荡信号能量明显低于模型对照组;②建模仿真实验:不加刺激时,健康大鼠beta频段功率谱密度峰值(30 dB)显著低于帕金森病大鼠(55 dB);施加经颅磁声电刺激后,两组大鼠beta频段功率谱密度值普遍降低;beta频段功率谱密度峰值与超声发射周期呈正相关、与感应电流密度呈负相关,当超声发射占空比为50%时功率谱密度峰值最低;③结果表明:经颅磁声电刺激可抑制健康与帕金森病大鼠的beta振荡,进而改善大鼠的运动功能与决策认知功能。

基于改进人工势场法的通用航空路径规划

通用航空飞机在飞行过程除了要面对障碍物和天气系统的威胁,同时也受到飞行空域的限制,往往飞机只能在一块固定的空域或狭小的飞行走廊内飞行,一旦飞出限制空域,则有可能引发飞行冲突,甚至发生严重的安全事故。针对这些问题,在人工势场法斥力势场函数中添加航空器和目标点之间的相对距离函数,首先解决传统人工势场法存在的目标不可达问题和局部极小点问题,然后在算法中加入航路边界斥力影响因子,使飞机避障后在边界斥力的作用下重回航路中心。经过MATLAB仿真验证,试验结果表明,改进后的人工势场法能够实现主动避障和飞机航迹的规划。

腺苷A1受体拮抗剂的长期干预对阿尔茨海默病模型小鼠认知功能的影响

目的探讨腺苷A1受体拮抗剂DPCPX的长期干预对阿尔茨海默病(Alzheimer’sdisease,AD)模型小鼠认知功能相关电生理指标、行为学表现及病理标志物的影响。方法使用7月龄C57BL/6J及APP/PS1小鼠,随机分为C57-对照组、C57-DPCPX组、APP/PS1-对照组及APP/PS1-DPCPX组,分别采用DPCPX(1mg/kg·d)或对照溶剂连续腹腔注射21d。采用Plexon系统记录小鼠海马CA1区局部场电位,MATLAB软件评估海马认知功能相关电生理指标——尖波涟漪(sharpwaveripples,SWRs)的特征,Morris水迷宫实验评估小鼠的空间记忆能力,免疫荧光染色检测海马内Aβ斑块沉积。结果分析4组小鼠认知功能相关电生理指标(SWRs)、行为学表现(Morris水迷宫)及脑组织Aβ检测结果发现:①在SWRs的平均数量及平均持续时间上,C57-对照组与C57-DPCPX组之间,APP/PS1-对照组与APP/PS1-DPCPX组之间差异均无统计学意义(均P>0.05),仅C57-对照组显著多于APP/PS1-对照组(P=0.0019,P=0.0202)。②Morris水迷宫实验中,在学习阶段的逃避潜伏期上,C57-对照组与C57-DPCPX组之间,APP/PS1-对照组与APP/PS1-DPCPX组之间差异均无统计学意义(均P>0.05),仅C57-对照组与APP/PS1-对照组相比显著缩短(P<0.05)。在探索阶段,在穿越平台次数及目标象限停留时间占比上,C57-对照组与C57-DPCPX组之间,APP/PS1-对照组与APP/PS1-DPCPX组之间差异均无统计学意义(均P>0.05),仅C57-对照组显著多于APP/PS1-对照组(P=0.0024,P=0.0415)。③在Aβ斑块的数量及面积上,APP/PS1-对照组与APP/PS1-DPCPX组相比差异均无统计学意义(均P>0.05)。结论腺苷A1受体拮抗剂DPCPX的长期干预不能显著改善AD模型小鼠的认知功能,提示对于AD这一具有复杂发病机制的疾病,仅针对单一靶点的干预很难达到显著改善认知功能的作用。

2,5-二甲氧基-4-甲基苯丙胺对大鼠眶额叶皮质低γ和高频振荡的影响

目的 探究经典致幻剂2,5-二甲氧基-4-甲基苯丙胺(DOM)致精神障碍的潜在电生理机制。方法 对成年雄性SD大鼠进行眶额叶皮质(OFC)微丝电极阵列植入手术,术后恢复1周,采用自身对照按以下给药顺序依次ip给药:DOM(0.5,1.5和3.0 mg·kg^(-1)),DOM 3.0 mg·kg^(-1)+5-羟色胺2A(5-HT_(2A))受体拮抗剂凯坦色林1.0 mg·kg^(-1),DOM 3.0 mg·kg^(-1)+5-HT_(2C)受体拮抗剂SB242084 3.0 mg·kg^(-1),凯坦色林1.0 mg·kg^(-1),SB242084 3.0 mg·kg^(-1)。每次药物处理前ip给予生理盐水作为对照组。每次药物处理间隔洗脱期1周。用Plexon在体多通道记录系统记录大鼠OFC脑区场电位,分析给药前后大鼠场电位变化。结果 与对照组相比,DOM(0.5,1.5和3.0 mg·kg^(-1))能够增加OFC脑区高频振荡(HFO)功率(P<0.05),降低低γ振荡功率(P<0.05,P<0.01);凯坦色林1.0 mg·kg^(-1)能够拮抗DOM引起的低γ(P<0.01)和HFO(P<0.05)功率的变化,SB242084 3.0 mg·kg^(-1)无拮抗作用。结论 DOM引起的幻觉等精神神经系统障碍可能与5-HT_(2A)受体介导的OFC脑区低γ振荡功率降低和HFO功率增加有关。

基于视野和速度引导的无人机集群避障算法

在未来的多无人机(unmanned aerial vehicle,UAV)空中作战中,无人机集群在未知空域中安全飞行是集群研究中的重要内容。针对无人机集群避障以及集群形态保持问题,提出了一种基于视野和速度引导(visual field and velocity guidance,VFVG)的集群避撞算法。基于视野法设计集群自适应通讯拓扑机制,结合远吸近斥势力原则及一致性方法,在保持集群形态的同时,加速了集群无人机个体间的避障信息的传递。在此基础上,提出将极限环与人工势场法相结合构造避障速度引导项,解决了集群遇障分群困难、避障徘徊停滞等问题。引入避障时间指标,验证了算法的避障效率。仿真结果表明,该方法能够使多无人机以良好的集群形态安全快速平稳地通过复杂障碍区域,有效提高了集群避障成功率和避障效率。

2,5-二甲氧基-4-碘苯丙胺对自由活动小鼠次级视觉皮质V2区γ振荡的作用

目的研究5-羟色胺2A受体(5-HT2AR)激动剂2,5-二甲氧基-4-碘苯丙胺(DOI)对自由活动小鼠次级视觉皮质V2区场电位的影响。方法将C57BL/6J小鼠手术埋置皮质脑电(ECOG)电极,恢复7 d后ip给予1%DMSO(溶剂),记录次级视觉皮质V2区局部场电位(LFP)30 min;而后ip给予DOI 2.0 mg·kg^(-1),记录该区LFP 30 min;最后ip给予5-HT2AR拮抗剂氟利色林0.3 mg·kg^(-1),记录该区LFP 30 min。将数据导入Neuro Explorer软件进行频谱分析,用GraphPad Prism 8.0.2软件分析给药前后γ振荡和θ振荡功率谱密度变化,用Matlab软件分析θ振荡和γ振荡相位振幅耦合。结果与给予溶剂相比,给予DOI 2.0 mg·kg^(-1)可显著增高次级视觉皮质V2区γ振荡(30~80 Hz)功率(P<0.05)和θ振荡(4~7 Hz)功率(P<0.05),显著降低θ振荡和γ振荡相位振幅耦合调制指数(P<0.01);氟利色林可逆转DOI引起的次级视觉皮质V2区γ振荡和θ振荡功率的增高(P<0.05)。结论DOI的致幻作用可能与其增高小鼠次级视觉皮质V2区γ振荡和θ振荡功率及降低θ振荡和γ振荡相位振幅耦合有关。

动态环境下自主机器人的双机制切向避障

针对机器人工作环境的动态随机性,提出面向双机制切向避障的改进人工势场法.针对传统人工势场法的局部极小值陷阱问题,提出静态避障机制,在规划开始前对地图进行预处理,预测局部极小值点并将障碍物分成连通与非连通障碍物,结合切向避障实现静态切向避障.以静态避障机制为基础,针对动态障碍物,提出动态避障机制,通过实时调整碰撞风险系数并选择系数最大的障碍物进行避障角补偿,实现动态切向避障.通过状态决策统筹静态、动态切向避障机制与全局路径规划,实现混合规划与设计.设计仿真和全向移动平台,对所提方法进行验证测试.结果表明,所提方法在不同环境复杂下均有效解决了传统人工势场法的局部极小值陷阱问题,实现了动态环境下快速自主避障.对比3种方法避开不同类型障碍物的平均耗时,所提方法比动态窗口法(DWA)提升55%,比时间弹性带法(TEB)提升40%;对比3种方法导航不同复杂度地图的平均耗时,所提方法比DWA提升39%,比TEB提升22%.

Cortico-striatal gamma oscillations are modulated by dopamine D3 receptors in dyskinetic rats

Long-term levodopa administration can lead to the development of levodopa-induced dyskinesia.Gamma oscillations are a widely recognized hallmark of abnormal neural electrical activity in levodopa-induced dyskinesia.Currently,studies have reported increased oscillation power in cases of levodopa-induced dyskinesia.However,little is known about how the other electrophysiological parameters of gamma oscillations are altered in levodopa-induced dyskinesia.Furthermore,the role of the dopamine D3 receptor,which is implicated in levodopa-induced dyskinesia,in movement disorder-related changes in neural oscillations is unclear.We found that the cortico-striatal functional connectivity of beta oscillations was enhanced in a model of Parkinson’s disease.Furthermore,levodopa application enhanced cortical gamma oscillations in cortico-striatal projections and cortical gamma aperiodic components,as well as bidirectional primary motor cortex(M1)↔dorsolateral striatum gamma flow.Administration of PD128907(a selective dopamine D3 receptor agonist)induced dyskinesia and excessive gamma oscillations with a bidirectional M1↔dorsolateral striatum flow.However,administration of PG01037(a selective dopamine D3 receptor antagonist)attenuated dyskinesia,suppressed gamma oscillations and cortical gamma aperiodic components,and decreased gamma causality in the M1→dorsolateral striatum direction.These findings suggest that the dopamine D3 receptor plays a role in dyskinesia-related oscillatory activity,and that it has potential as a therapeutic target for levodopa-induced dyskinesia.

基于APF-LSTM-DDPG算法的移动机器人局部路径规划

针对深度强化学习算法存在训练时间长、收敛速度慢的问题,将深度确定性策略梯度(deep deterministic policy gradient,DDPG)算法和人工势场(artifical potential field,APF)法相融合,引入长短期记忆(long short-term memory,LSTM)神经网络结构,提出了APF-LSTM-DDPG算法。首先在DDPG算法中添加LSTM,通过记忆单元和遗忘单元将奖励较高的样本优先学习,使模型更快地收敛;其次引入人工势场法,设计相应势场函数,解决环境奖励稀疏的缺点,加速模型收敛进程;然后通过人工势场法修正算法的动作选择,缩短路径长度;最后在机器人仿真平台(robot operating system,ROS)中搭建不同障碍物环境对算法进行了仿真验证。仿真结果表明,APF-LSTM-DDPG算法在搭建的仿真环境中训练时平均奖励能够更快地稳定,提高了算法的成功率并减少了规划路径中的冗余。

基于spike-LFP同步的神经元朝向选择性分析

局部场电位(local field potential,LFP)与神经元发放的锋电位(spike)之间的同步关系揭示了重要的神经编码信息。为了研究不同对比度的光栅刺激下猕猴视皮层V1区和V4区神经元的朝向选择性,本文将锋电位触发的相关矩阵同步方法应用于在猕猴视皮层V1区和V4区记录的微电极信号,发现spike与gamma频段LFP之间的同步与光栅朝向之间存在较强的相关性,反映了视觉刺激的基本特征信息。另外,神经元spike的发放速率虽然会受到光栅朝向的影响,但是在不同对比度下发放速率并无明显区别,而spike-LFP同步会随着对比度的增加而增加,能够反映出同一朝向下对比度的变化。本文还利用圆方差来量化spike-LFP同步的朝向调谐曲线,发现对比度越大,V1区和V4区神经元的朝向选择性越强,V1区神经元比V4区神经元具有更强的朝向选择性。总之,spike-LFP同步能够更深入地揭示视皮层神经元的朝向调谐特性,为研究朝向选择性的形成机制提供新的方向。