Babadi Baktash
School of Cognitive Sciences (SCS), Institute for Studies in Theoretical Physics and Mathematics (IPM), Niavaran Square, Tehran, PO Box 19395-5746, Iran.
J Comput Neurosci. 2005 Mar-Apr;18(2):229-43. doi: 10.1007/s10827-005-6560-5.
In recent years, accumulating evidence indicates that thalamic bursts are present during wakefulness and participate in information transmission as an effective relay mode with distinctive properties from the tonic activity. Thalamic bursts originate from activation of the low threshold calcium cannels via a local feedback inhibition, exerted by the thalamic reticular neurons upon the relay neurons. This article, examines if this simple mechanism is sufficient to explain the distinctive properties of thalamic bursting as an effective relay mode. A minimal model of thalamic circuit composed of a retinal spike train, a relay neuron and a reticular neuron is simulated to generate the tonic and burst firing modes. The integrate-and-fire-or-burst model is used to simulate the neurons. After discriminating the burst events with criteria based on inter-spike-intervals, statistical indices show that the bursts of the minimal model are stereotypic events. The relation between the rate of bursts and the parameters of the input spike train demonstrates marked nonlinearities. Burst response is shown to be selective to spike-silence-spike sequences in the input spike train. Moreover, burst events represent the input more reliably than the tonic spike in a considerable range of the parameters of the model. In conclusion, many of the distinctive properties of thalamic bursts such as stereotypy, nonlinear dependence on the sensory stimulus, feature selectivity and reliability are reproducible in the minimal model. Furthermore, the minimal model predicts that while the bursts are more frequent in the spike train of the off-center X relay neurons (corresponding to off-center X retinal ganglion cells), they are more reliable when generated by the on-center ones (corresponding to on-center X ganglion cells).
近年来，越来越多的证据表明，丘脑爆发在清醒状态下存在，并作为一种与紧张性活动具有不同特性的有效中继模式参与信息传递。丘脑爆发起源于低阈值钙通道的激活，这是通过丘脑网状神经元对中继神经元施加的局部反馈抑制实现的。本文探讨了这种简单机制是否足以解释丘脑爆发作为一种有效中继模式的独特特性。模拟了一个由视网膜尖峰序列、一个中继神经元和一个网状神经元组成的丘脑回路最小模型，以产生紧张性和爆发性放电模式。使用积分-发放-爆发模型来模拟神经元。在用基于峰峰间期的标准区分爆发事件后，统计指标表明最小模型的爆发是刻板事件。爆发频率与输入尖峰序列参数之间的关系显示出明显的非线性。爆发响应被证明对输入尖峰序列中的峰-静息-峰序列具有选择性。此外，在模型的相当一部分参数范围内，爆发事件比紧张性尖峰更可靠地代表输入。总之，丘脑爆发的许多独特特性，如刻板性、对感觉刺激的非线性依赖、特征选择性和可靠性，在最小模型中是可重现的。此外，最小模型预测，虽然爆发在偏心X中继神经元（对应于偏心X视网膜神经节细胞）的尖峰序列中更频繁，但由中心on型神经元（对应于中心on型神经节细胞）产生时更可靠。
