Bazhenov M, Timofeev I, Steriade M, Sejnowski T J
Howard Hughes Medical Institute, The Salk Institute, Computational Neurobiology Laboratory, La Jolla, California 92037, USA.
J Neurosci. 1998 Aug 15;18(16):6444-65. doi: 10.1523/JNEUROSCI.18-16-06444.1998.
Repetitive stimulation of the dorsal thalamus at 7-14 Hz produces an increasing number of spikes at an increasing frequency in neocortical neurons during the first few stimuli. Possible mechanisms underlying these cortical augmenting responses were analyzed with a computer model that included populations of thalamocortical cells, thalamic reticular neurons, up to two layers of cortical pyramidal cells, and cortical inhibitory interneurons. Repetitive thalamic stimulation produced a low-threshold intrathalamic augmentation in the model based on the deinactivation of the low-threshold Ca2+ current in thalamocortical cells, which in turn induced cortical augmenting responses. In the cortical model, augmenting responses were more powerful in the "input" layer compared with those in the "output" layer. Cortical stimulation of the network model produced augmenting responses in cortical neurons in distant cortical areas through corticothalamocortical loops and low-threshold intrathalamic augmentation. Thalamic stimulation was more effective in eliciting augmenting responses than cortical stimulation. Intracortical inhibition had an important influence on the genesis of augmenting responses in cortical neurons: A shift in the balance between intracortical excitation and inhibition toward excitation transformed an augmenting responses to long-lasting paroxysmal discharge. The predictions of the model were compared with in vivo recordings from neurons in cortical area 4 and thalamic ventrolateral nucleus of anesthetized cats. The known intrinsic properties of thalamic cells and thalamocortical interconnections can account for the basic properties of cortical augmenting responses.
在最初几次刺激期间，以7 - 14赫兹的频率重复刺激背侧丘脑，会使新皮层神经元产生的动作电位数量增加，频率也不断上升。我们使用一个计算机模型分析了这些皮层增强反应背后可能的机制，该模型包含丘脑皮质细胞群、丘脑网状神经元、多达两层的皮层锥体细胞以及皮层抑制性中间神经元。重复丘脑刺激在模型中产生了基于丘脑皮质细胞低阈值Ca2+电流去失活的低阈值丘脑内增强，这反过来又诱导了皮层增强反应。在皮层模型中，“输入”层的增强反应比“输出”层更强烈。对网络模型的皮层刺激通过皮质 - 丘脑 - 皮质环路和低阈值丘脑内增强，在远处皮层区域的皮层神经元中产生增强反应。丘脑刺激在引发增强反应方面比皮层刺激更有效。皮层内抑制对皮层神经元增强反应的产生有重要影响：皮层内兴奋与抑制之间的平衡向兴奋方向转变会将增强反应转变为持久的阵发性放电。将该模型的预测结果与麻醉猫的皮层4区和丘脑腹外侧核神经元的体内记录进行了比较。丘脑细胞的已知内在特性和丘脑 - 皮质相互连接可以解释皮层增强反应的基本特性。
