Spike and burst coding in thalamocortical relay cells.
Spike and burst coding in thalamocortical relay cells.
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DOI：
10.1371/journal.pcbi.1005960
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发表时间：
2018-03
影响因子：
4.3
通讯作者：
Wadman WJ
中科院分区：
文献类型：
--
作者：
Zeldenrust F;Chameau P;Wadman WJ
哺乳动物丘脑皮质中继（TCR）神经元在强直性尖峰和爆发状态之间转换其放电活动。在一项结合实验和计算的研究中，我们研究了输出尖峰序列中单个尖峰和脉冲所代表的输入信号的特征，以及这种编码如何受到神经元膜电压状态的影响。将相同的冻结高斯噪声电流迹注射到大鼠脑切片的TCR神经元和验证的三室TCR模型细胞中。通过计算相干性和阻抗，分析了得到的膜电压走线和尖峰列。反向相关技术给出了事件触发平均（ETA）和事件触发协方差（ETC）。这表明，特征选择性在事件发生之前很久就开始了（长达300毫秒），并显示出峰值（对波动的选择性）和爆发（对整合的选择性）之间的明显区别。对模型单元进行了微调，以模拟实验精度范围内的冻结噪声引发的尖峰和突发响应，特别是对于混合模式。计算了信号中各类事件以及整个信号所携带的信息量。脉冲锁相并以比单尖峰更低的频率传输信息。在去极化过程中，神经元平滑地从以爆发为主的状态过渡到对高频波动更为敏感的尖峰状态。然后，该模型用于阐明无法通过实验评估的特性，特别是两个重要的亚阈值电压依赖电流的作用：低阈值激活钙电流（IT）和环核苷酸调制的h电流（Ih）。这些电流的eta及其潜在的激活/失活状态不仅解释了放电状态的依赖关系，而且解释了两种电流长期协调的动态作用。最后，该模型用于研究更现实的“高导状态”，其中波动是由（突触）电导变化而不是电流注入引起的。在“标准”条件下，由于t型钙电流的高度失活，爆发很难启动。强和/或精确定时的抑制电流能够消除这种失活。大脑中的神经元对（感官）刺激作出反应，产生被称为“尖峰”或“动作电位”的电脉冲。尖峰以不同的时间模式组织，例如“爆发”，它们以高频率出现，然后是一段时间的沉默。爆发在神经系统中无处不在：它们发生在大脑的不同部位和不同的物种中。已经指出了产生它们的不同机制。为什么神经系统在交流中使用脉冲，或者脉冲代表什么类型的信息，在很大程度上仍然未知。在这里，我们观察了丘脑皮质中继（TCR）细胞的破裂，这些神经元在早期感觉处理和高阶结构（皮层）之间形成桥梁。由于激活了两种不同的亚阈值离子电流：t型钙电流和h型钙电流，这些细胞产生了脉冲放电。我们通过实验和计算研究了输入中的哪些特征使TCR细胞响应脉冲，哪些特征具有单尖峰。脉冲是对低频缓慢增加的输入的响应；单次尖峰是对快速波动的反应。此外，爆发是罕见的，信息量很大，这与之前的假设一致，即爆发可以在神经系统中起到“叫醒电话”的作用。
Mammalian thalamocortical relay (TCR) neurons switch their firing activity between a tonic spiking and a bursting regime. In a combined experimental and computational study, we investigated the features in the input signal that single spikes and bursts in the output spike train represent and how this code is influenced by the membrane voltage state of the neuron. Identical frozen Gaussian noise current traces were injected into TCR neurons in rat brain slices as well as in a validated three-compartment TCR model cell. The resulting membrane voltage traces and spike trains were analyzed by calculating the coherence and impedance. Reverse correlation techniques gave the Event-Triggered Average (ETA) and the Event-Triggered Covariance (ETC). This demonstrated that the feature selectivity started relatively long before the events (up to 300 ms) and showed a clear distinction between spikes (selective for fluctuations) and bursts (selective for integration). The model cell was fine-tuned to mimic the frozen noise initiated spike and burst responses to within experimental accuracy, especially for the mixed mode regimes. The information content carried by the various types of events in the signal as well as by the whole signal was calculated. Bursts phase-lock to and transfer information at lower frequencies than single spikes. On depolarization the neuron transits smoothly from the predominantly bursting regime to a spiking regime, in which it is more sensitive to high-frequency fluctuations. The model was then used to elucidate properties that could not be assessed experimentally, in particular the role of two important subthreshold voltage-dependent currents: the low threshold activated calcium current (IT) and the cyclic nucleotide modulated h current (Ih). The ETAs of those currents and their underlying activation/inactivation states not only explained the state dependence of the firing regime but also the long-lasting concerted dynamic action of the two currents. Finally, the model was used to investigate the more realistic “high-conductance state”, where fluctuations are caused by (synaptic) conductance changes instead of current injection. Under “standard” conditions bursts are difficult to initiate, given the high degree of inactivation of the T-type calcium current. Strong and/or precisely timed inhibitory currents were able to remove this inactivation. Neurons in the brain respond to (sensory) stimuli by generating electrical pulses called ‘spikes’ or ‘action potentials’. Spikes are organized in different temporal patterns, such as ‘bursts’ in which they occur at a high frequency followed by a period of silence. Bursts are ubiquitous in the nervous system: they occur in different parts of the brain and in different species. Different mechanisms that generate them have been pointed out. Why the nervous system uses bursts in its communication, or what type of information is represented by bursts, remains largely unknown. Here, we looked at bursting in thalamocortical relay (TCR) cells, neurons that form a bridge between early sensory processing and higher-order structures (cortex). These cells fire bursts as a result of the activation of two distinct subthreshold ionic currents: the T-type calcium current and the h-type current. We investigated experimentally and computationally what features in the input makes TCR cells respond with bursts, and what features with single spikes. Bursts are a response to low-frequency slowly increasing input; single spikes are a response to faster fluctuations. Moreover, bursts are rare and highly informative, in line with an earlier hypothesis that bursts could play a ‘wake-up call’ role in the nervous system.
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影响因子：
4.3
作者：
Eyherabide HG;Rokem A;Herz AV;Samengo I
通讯作者：
Samengo I
影响因子：
3.4
作者：
DESTEXHE, A;BABLOYANTZ, A;SEJNOWSKI, TJ
通讯作者：
SEJNOWSKI, TJ
影响因子：
2.5
作者：
Destexhe, A;Bal, T;Sejnowski, TJ
通讯作者：
Sejnowski, TJ
影响因子：
2.9
作者：
Arcas, BAY;Fairhall, AL;Bialek, W
通讯作者：
Bialek, W
影响因子：
5.3
作者：
Destexhe, A;Neubig, M;Huguenard, J
通讯作者：
Huguenard, J