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参考文献 1
Marsden C D.Parkinson′s disease.Journal of Neurology,Neurosurgery & Psychiatry,1994,57(6):672~ 681
参考文献 2
Mount M P,Lira A,Grimes D,et al.Involvement of in-terferon-gamma in microglial-mediated loss of dopaminer-gic neurons.Journal of Neuroscience,2007,27(12):3328 ~ 3337
参考文献 3
Nambu A,Tachibana Y,Chiken S.Cause of parkinsonian symptoms:firing rate,firing pattern or dynamic activity changes?Basal Ganglia,2015,5(1):1~ 6
参考文献 4
DeLong M R.Primate models of movement disorders of basal ganglia origin.Trends Neurosciences,1990,13(7),281~ 285
参考文献 5
陈晓光,周奋,刘真,等.苍白球内侧部摧毁术治疗帕金森病概率功能图谱再研究.立体定向和功能神经外科杂志,2011,24(4):246 ~ 248(Chen X G,Zhou F,Liu Z,et al.Re-study on the probability functional map of parkinson′s disease treated by medial pallidotomy.Journal of Stereotactic and Functional Neurosurgery,2011,24(4):246~ 248(in Chinese))
参考文献 6
贾洪军.基于基底核模型的DBS作用机制研究[硕士学位论文].天津:天津大学,2012(Jia H J.Study on the mechanism of DBS based on basal nucleus model[Master Thesis].Tianjin:Tianjin University,2012(in Chinese))
参考文献 7
Worth P F.How to treat Parkinson′s disease in 2013.Clinical Medicine,2013,13(1):93~ 96
参考文献 8
Montgomery E B,Gale J T.Mechanisms of action of deep brain stimulation(DBS).Neuroscience and Biobehavioral Reviews,2008,32(3):388~ 407
参考文献 9
Holgado A J N,Terry J,Bogacz R.Conditions for the generation of beta band activity in Parkinson′s disease.Bmc Neuroscience,2009,10(Suppl.1):1~ 2
参考文献 10
Nambu A,Tachibana Y.Mechanism of parkinsonian neu-ronal oscillations in the primate basal ganglia:some con-siderations based on our recent work.Frontiers in Systems Neuroscience,2014,8:74
参考文献 11
Pavlides A,Hogan S J,Bogacz R.Computational models describing possible mechanisms for generation of excessive beta oscillations in Parkinson′s Disease.Plos Computa-tional Biology,2015,11(12):e1004609
参考文献 12
Yan H,Wang J.Quantification of motor network dynamics in Parkinson′s disease by means of landscape and flux theory.Plos One,2017,12(3):e0174364
参考文献 13
Hu B,Chen B,Chi H.Controlling absence seizures by tuning activation level of the thalamus and striatum.Chaos Solitons & Fractals,2017,95:65~ 76
参考文献 14
Dayan P,Abbott L F.Theoretical neuroscience:computa-tional and mathematical modeling of neural systems.Mas-sachusetts:The MIT Press,2005
参考文献 15
McCarthy M M,Moore-Kochlacs C,Gu X,et al.Striatal origin of the pathologic beta oscillations in Parkinson′ s disease.Proceedings of the National Academy of Sciences,2011,108(28):11620~ 11625
参考文献 16
张巧俊,蔺雪梅,刘健,等.单侧黑质纹状体通路损毁诱发大鼠伏核神经元放电频率增加.西安交通大学学报(医学版),2008,29(6):609 ~ 612(Zhang Q J,Lin X M,Liu J,et al.Increased firing frequency of nucleus ac-cumbens neurons in rats induced by unilateral striatum nigra pathway lesion.Journal of Xi′an Jiaotong University(Medical Edition),2008,29(6):609 ~ 612(in Chi-nese))
参考文献 17
王贵元,杨卓琴.非线性时滞奇异系统的严格实用稳定性研究.动力学与控制学报,2018,16(4):317 ~ 323(Wang G Y,Yang Z Q.Strict practical stability of nonlin-ear singular systems with time delay.Journal of Dynamics and Control,2018,16(4):317~ 323(in Chinese))
参考文献 18
赵松,杨卓琴.四阶血细胞生成系统的双参数分岔分析.动力学与控制学报,2017,15(5):472 ~ 475(Zhao S,Yang Z Q.Two-parameter bifurcation analysis of fourth or-der hematopoiesis.Journal of Dynamics and Control,2017,15(5):472~ 475(in Chinese))
目录contents

    摘要

    探究大脑基底神经节中丘脑底核和苍白球神经核团振荡动力学的起源对理解帕金森病的发病机理起到重要作用.本文建立了较为完整的关于帕金森病的神经网络模型,该模型含有兴奋和抑制神经元的大脑皮质、由纹状体、丘脑底核、苍白球内侧和外侧构成的基底神经节以及丘脑.首先,通过对模型进行数值模拟, 所得的动力学结果与丘脑底核和苍白球振荡相关的生物实验结果一致.其次,探讨了与丘脑底核和苍白球神经核团相关的突触连接强度对他们振荡动力学的影响.我们的结果显示,丘脑底核同时受到纹状体较强的促进作用和苍白球外侧较弱的抑制作用时它的振荡消失.而当苍白球同时受到丘脑底核较强的促进作用和纹状体对它的抑制作用时,苍白球的振荡增强.希望本文的研究结果对帕金森病的治疗有一定的指导作用.

    Abstract

    Exploring the origin of oscillation dynamics of subthalamic nucleus and globus pallidus in basal gan- glia plays an important role in understanding the pathogenesis of Parkinson′s disease.In this paper,a more com- plete neural network model for Parkinson′s disease is established.The model contains the cortex with excitatory and inhibitory neurons,basal ganglia composed of striatum,subthalamic nucleus,external and internal segment of globus pallidus and thalamus.First,the dynamic results obtained through numerical simulation of the model are consistent with the biological experimental results related to the oscillations in the subthalamic nucleus and the globus pallidus.Secondly,the effects of synaptic connection weights associated with subthalamic nucleus and glo- bus pallidus on their oscillation dynamics were discussed.Our results show that the oscillation in the subthalamic nucleus will disappear for stronger excitatory connection weights from the striatum and weaker inhibitory connec- tion weights from external segment of globus pallidus.Also,oscillation in the globus pallidus will appear for both stronger excitatory and inhibitory connection weights from the subthalamic nucleus the striatum,respectively.It is hoped that the results of this study will play a guiding role in the treatment of Parkinson′s disease.

    Keywords

    Parkinson′sdiseaseneuralnetworkbasalgangliaoscillationdynamics

  • 0 引言

  • 帕金森病(Parkinson’s disease,PD)是常见的神经退行性疾病,其病状包括震颤、肌肉僵直、运动减少等运动症状[1].这些运动症状起源于大脑黑质致密部内多巴胺能神经元的异常死亡[2],并影响到整个皮质(cortex,Ctx)、基底神经节( basal ganglia, BG)和丘脑( thalamus,TH)环路(BGCT) 的神经元活动,尤其是基底神经节中的丘脑底核(Subthalam-ic nucleus,STN) 和苍白球(Globus pallidus,GP) 神经核团出现异常同步振荡[3] .因此,需要更多的研究来探索STN和GP的振荡起源来理解帕金森病的发病机理.

  • 许多模型探究了BGCT回路中产生振荡的起源问题[4-8].一些研究认为帕金森病的振荡行为起因于STN与苍白球外侧( External segment of the globus pallidus,GPe) 间的抑制和兴奋环路( STN-GPe) [9].但是,Tachibana等人的实验结果显示Ctx对STN和GP的振荡也有较大影响[10] ,Pavlides等人构造了Ctx-STN-GPe环路并拟合了此实验结果[11],其中Ctx中包含兴奋和抑制神经元.此外,HanYan等人建立了Ctx-BG-TH模型[12] ,其中,基底神经节中的纹状体( Striatum,Str) 中包含了D1 和D2 类神经元,并利用能量面的方法分析了多巴胺对Ctx和TH活动的影响.因此,有必要将Ctx中的兴奋和抑制神经元以及Str中的D1 和D2 类神经元考虑到Ctx-BG-TH模型中来模拟实验结果,并分析BG中STN和GP振荡的机理.

  • 本文结合文献[11][12]中的模型而构造了更加完整的Ctx-BG-TH模型.首先,验证了模型的数值结果与Tachibana等人的实验结果一致,然后探讨了BG中与STN和GP相关的权重对其振荡的影响.最后给出结论.

  • 1 模型与方程

  • 为模拟Tachibana等人的实验结果,我们构造了图1 的BGCT模型.模型包括Ctx、BG和TH以及他们间的相互作用.Ctx包含兴奋性椎体神经元(excitatory pyramidal neurons,E)和抑制性椎体神经元( inhibitory pyramidal neurons,I) [10,12],E向I投射兴奋信号.文中假设E对自身有一个正反馈且I受到常数输入C的抑制.此外,E还向BG中的STN和Str中D1( Striatum D1,D1) 和D2( Striatum D2, D2)神经元输入兴奋信号.进一步STN把兴奋信号传入苍白球内侧(Internal segment of the globus pal-lidus,GPi)和GPe.黑质纹状体的多巴胺分别激活和抑制D1和D2神经元,进而将抑制信号分别传给GPi和GPe [3,13],可见Str与STN形成了对立关系.此外,GPe对STN传递抑制信号,形成了GPe-STN负反馈回路; GPe同时也抑制GPi,GPi作为BG的输出部位对TH传递了抑制信号,使得Ctx接收到来自TH的兴奋性信号减弱.

  • 图1 皮质-基底神经节-丘脑网络

  • Fig.1 Network of Ctx-BG-TH

  • 图1 所示的BGCT网络由方程组(1)-(8)描述,方程的建立参考文献[14],为了简化,我们忽略了神经元间时滞的作用.下角标i=1,‧‧‧,8 分别表示神经核团I、E、D1 、D2 、GPi、GPe、STN和TH,其中f i 表示第i个神经核团的放电率,τi 表示第i个神经核团的膜时间常数, ij表示神经核团i和j之间的连接强度,′表示对时间的一阶导数.

  • τ1f1'=G1(w21f2-C)-f1
    (1)
  • τ2f2'=G2(-w12f1+w22f2+w82f8)-f2
    (2)
  • τ3f3'=G3(w23f2)-f3
    (3)
  • τ4f4'=G4(w24f2)-f4
    (4)
  • τ5f5'=G5(-w35f3-w65f6+w75f7)-f5
    (5)
  • τ6f6'=G6(-w46f4+w76f7)-f6
    (6)
  • τ7f7'=G7(w27f2-w62f6)-f7
    (7)
  • τ8f8'=G8(-w58f5)-f8
    (8)
  • Gi(in)是关于突触输入in的激活函数[6],满足下式:

  • Gi(in)=Mi1+(Mi-BiBiexp)(-4inBi)
    (9)
  • 其中,Bi 和Mi 分别表示第i个神经核团的基础放电率和最大放电率

  • 为了模拟实验结果,所有参数均在其合理范围内选取值,τi=10ms,Bi=15spk/s和Mi=240spk/s, w35=3, 76=6,其他wij =5.C=150spk/s.除特别说明以外,参数均取以上的值

  • 2 结果与分析

  • 2.1 对Tachibana实验的模拟

  • 在本节,通过改变BGCT环路中的连接权重来模拟Tachibana实验中STN和GPe的活动[10].

  • 首先,实验分别验证了Ctx和GPe与STN的连接强度对STN振荡的影响.实验中先向STN中注射谷氨酸受体拮抗剂,使其不能接收Ctx的兴奋信号,则STN平均放电率减小且振荡消失.我们令方程中w27=0,图2(a)描述了STN放电率的时间历程,与实验结果一致.另外,实验中向GPe注射 γ 氨基丁酸受体激动剂,抑制其活动,进而减少对STN的抑制作用,则STN的平均放电率增加,振荡消失.我们令w67 =0,图2(b)中STN放电率的时间历程图与实验结果一致.

  • 图2 STN放电率的时间历程图

  • Fig.2 Time series of STN firing rate

  • 其次,验证了Str和STN与GP间的连接权值对GP振荡的影响.本文中,为了统一刻画STN对GPe和GPi的激活作用,令w75=5α, 76=6α,α 刻画了STN对GP作用强度.实验中对STN注射 γ 氨基丁酸受体激动剂,进而阻断STN对GP的兴奋信号,使得GPi和GPe的平均速率均下降.当 α=0 时,STN对GP的作用阻断,得到图3(a1)和(a2)的GPi和GPe放电速率的时间历程图,与实验结果一致.另外,在GPe/GPi中注射 γ 氨基丁酸受体拮抗剂,阻断了GP接收抑制信号,则GPi/GPe的平均放电率增加,GPi的振荡加强,GPe的振荡变化较小.同样,我们令w35=3β, 46=5β,β 可以刻画Str对GP的抑制强度.当 β=0, 65=0 时,阻断了GP的所有抑制信号,得到GPi和GPe放电速率的时间历程图(图3( b1)和( b2)),与实验结果一致.此外,实验表明阻断Str对GP的输入会使得GP的振荡消失[15,16],我们令 β=0,得到图3( c1)和( c2)的GP放电速率时间历程图,与实验结果一致.

  • 图3 GP放电率的时间历程图

  • Fig.3 Time series of GP firing rate

  • 以上通过调节Ctx和GPe对STN的连接权重w27和w67以及刻画STN和Str对GP的连接权重的参数 α 和 β,使得模型的数值结果与实验结果一致.为了更详细地了解这些连接权重对其振荡的影响, 下面给出这些参数对STN和GP振幅的影响.

  • 2.2 STN连接权重对STN振荡的影响

  • 本节分析了Ctx和GPe与STN的连接权重w27 和w67对STN放电速率最大值和最小值的影响,进而得到对STN振荡的影响.图4 给出了STN放电率关于参数w27的变化情况,当参数在区域B内变化时(0.046<w27 <5.01),STN出现振荡,而对于区域A(w27 <0.046)和区域C(w27 >5.01)内的参数,STN的振荡消失,在区域A内的放电速率较小,而在区域C内放电速率较大.

  • 类似地,图5 给出了w67对STN放电率的影响, 当参数在区域B内(4.54<w67<6)),STN产生振荡, 在区域A内(w67 <4.54),STN的振荡消失.因此Ctx与STN间较大的连接权值和GPe与STN间较小的连接权重使STN振荡消失.

  • 图4 w27对STN放电率的影响, 其中“ ×”表示放电率的最大和最小值Fig.4 The effect of w27 on STN firing rate, “ ×” is maximum and minmum of STN firing rate

  • 图5 w67对STN放电率的影响.其中“ ×”表示放电率的最大和最小值Fig.5 The effect of w67 on STN firing rate, “ ×” is maximum and minmum of STN firing rate

  • 为了更全面地探讨w27和w67对STN振荡的影响,图6 给出了STN振幅与w27和w67的关系.整个参数平面分为三部分,区域A和C内的参数使STN的振荡消失,而其他区域使STN出现振荡.较大的w27和较小的w67更易使得STN的振荡消失.

  • 图6 w27和w67对STN振幅的影响

  • Fig.6 The effect of w27 and w67 on amplitude of STN firing rate

  • 2.3 GP连接权重对GP振荡的影响

  • GP受STN和Str的调控作用,α 和 β 分别反映了STN和Str连接GP的突触强度,由于GPi和GPe的放电率不完全相同,我们用他们放电率的平均值反映GP的放电率.然后分别探讨了 α、β 对GP放电率最大值和最小值的影响(图7 和图8).

  • 从图7 可以看出,区域A、C和E内的 α 使得GP达到稳态,振荡消失,在区域A内,GP放电速率很小,而在区域C和E内,GP放电速率较大.当 α 在区域B和D内,GP产生振荡,振幅在区域B内较小而区域D内较大.根据图8,当 β 在区域B时,GP产生振荡,而当 β 位于区域A和C内,GP振荡消失.

  • 图7 α 对GP放电率的影响, 其中“ ×”表示放电率的最大和最小值

  • Fig.7 The effect of α on GP firing rate, “ ×” is maximum and minmum of GP firing rate

  • 图8 β 对GP放电率的影响, 其中“ ×”表示放电率的最大和最小值

  • Fig.8 The effect of β on GP firing rate, “ ×” is maximum and minmum of STN firing rate

  • 类似的,图9 给出参数 α 和 β 对GP放电率振幅的影响,可以看出参数区域分为五部分,当参数在区域A、B和C内变化时,GP振荡消失,而在此区域外,GP出现振荡,区域B和C之间的振荡幅度较小,而在区域A和B间振幅较大,可以看出当STN和Ctx对GP的作用同时增强时,更容易使得GP发生振荡,与实验结果一致[8].

  • 图9 α,β 对GP振幅的影响

  • Fig.9 The effect of the amplitude of GP firing rate

  • 3 结论

  • 本文构造了一个较完整的BGCT模型,并模拟出实验结果.重点探讨了Ctx对STN兴奋作用强度和GPe对STN抑制作用强度对STN放电速率振荡的影响,可以看出Ctx对STN较强的促进作用和GPe对STN较小的抑制作用使得STN的振荡消失.此外,讨论了STN对GP的促进作用强度以及Str对GP的抑制作用强度对GP放电率振荡的影响, 可以看出,当他们的作用同时增强时,更容易使得GP发生高幅振荡.当然,有必要进一步利用理论和数值模拟方法[17,18]探讨网络中其他连接强度以及神经元间的时滞等其他生物条件对基底神经节振荡的影响.

  • 参考文献

    • [1] Marsden C D.Parkinson′s disease.Journal of Neurology,Neurosurgery & Psychiatry,1994,57(6):672~ 681

    • [2] Mount M P,Lira A,Grimes D,et al.Involvement of in-terferon-gamma in microglial-mediated loss of dopaminer-gic neurons.Journal of Neuroscience,2007,27(12):3328 ~ 3337

    • [3] Nambu A,Tachibana Y,Chiken S.Cause of parkinsonian symptoms:firing rate,firing pattern or dynamic activity changes?Basal Ganglia,2015,5(1):1~ 6

    • [4] DeLong M R.Primate models of movement disorders of basal ganglia origin.Trends Neurosciences,1990,13(7),281~ 285

    • [5] 陈晓光,周奋,刘真,等.苍白球内侧部摧毁术治疗帕金森病概率功能图谱再研究.立体定向和功能神经外科杂志,2011,24(4):246 ~ 248(Chen X G,Zhou F,Liu Z,et al.Re-study on the probability functional map of parkinson′s disease treated by medial pallidotomy.Journal of Stereotactic and Functional Neurosurgery,2011,24(4):246~ 248(in Chinese))

    • [6] 贾洪军.基于基底核模型的DBS作用机制研究[硕士学位论文].天津:天津大学,2012(Jia H J.Study on the mechanism of DBS based on basal nucleus model[Master Thesis].Tianjin:Tianjin University,2012(in Chinese))

    • [7] Worth P F.How to treat Parkinson′s disease in 2013.Clinical Medicine,2013,13(1):93~ 96

    • [8] Montgomery E B,Gale J T.Mechanisms of action of deep brain stimulation(DBS).Neuroscience and Biobehavioral Reviews,2008,32(3):388~ 407

    • [9] Holgado A J N,Terry J,Bogacz R.Conditions for the generation of beta band activity in Parkinson′s disease.Bmc Neuroscience,2009,10(Suppl.1):1~ 2

    • [10] Nambu A,Tachibana Y.Mechanism of parkinsonian neu-ronal oscillations in the primate basal ganglia:some con-siderations based on our recent work.Frontiers in Systems Neuroscience,2014,8:74

    • [11] Pavlides A,Hogan S J,Bogacz R.Computational models describing possible mechanisms for generation of excessive beta oscillations in Parkinson′s Disease.Plos Computa-tional Biology,2015,11(12):e1004609

    • [12] Yan H,Wang J.Quantification of motor network dynamics in Parkinson′s disease by means of landscape and flux theory.Plos One,2017,12(3):e0174364

    • [13] Hu B,Chen B,Chi H.Controlling absence seizures by tuning activation level of the thalamus and striatum.Chaos Solitons & Fractals,2017,95:65~ 76

    • [14] Dayan P,Abbott L F.Theoretical neuroscience:computa-tional and mathematical modeling of neural systems.Mas-sachusetts:The MIT Press,2005

    • [15] McCarthy M M,Moore-Kochlacs C,Gu X,et al.Striatal origin of the pathologic beta oscillations in Parkinson′ s disease.Proceedings of the National Academy of Sciences,2011,108(28):11620~ 11625

    • [16] 张巧俊,蔺雪梅,刘健,等.单侧黑质纹状体通路损毁诱发大鼠伏核神经元放电频率增加.西安交通大学学报(医学版),2008,29(6):609 ~ 612(Zhang Q J,Lin X M,Liu J,et al.Increased firing frequency of nucleus ac-cumbens neurons in rats induced by unilateral striatum nigra pathway lesion.Journal of Xi′an Jiaotong University(Medical Edition),2008,29(6):609 ~ 612(in Chi-nese))

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