Spike-rate coding and spike-time coding are affected oppositely by different adaptation mechanisms.
Spike-rate coding and spike-time coding are affected oppositely by different adaptation mechanisms.
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DOI：
10.1523/jneurosci.1792-08.2008
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发表时间：
2008-12-10
期刊：
影响因子：
--
通讯作者：
Sejnowski TJ
中科院分区：
文献类型：
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作者：
Prescott SA;Sejnowski TJ
峰电位频率适应在长时间刺激期间会导致峰电位减少，但适应对神经编码的全面影响要复杂得多，特别是如果考虑到介导适应的生物物理机制的多样性以及神经信息可被编码的不同方式。在此，我们表明，根据神经编码策略以及负责适应的生物物理机制，适应具有相反的效应。在有噪声的条件下，钙激活的钾离子电流（IAHP）通过使缓慢或恒定输入所引发的峰电位序列规则化，以牺牲峰电位时间编码为代价改善了有效的峰电位频率编码；噪声功率在高频时增加，但在低频时降低，这与改善低频信号编码的噪声整形是一致的。相比之下，电压激活的M型钾离子电流（IM）通过阻止神经元对缓慢输入重复产生峰电位，从而使其能够针对快速输入产生孤立的、时间精准的峰电位，以牺牲峰电位频率编码为代价改善了峰电位时间编码。利用动力系统分析，我们展示了IAHP如何将高频噪声对峰电位间期的扰动降至最低，而IM如何将重复峰电位对峰电位时间准确性的破坏降至最低。这种二分的结果与IAHP和IM不同的激活要求直接相关，这反过来又决定了这些电流是对峰电位还是膜电位介导负反馈。因此，基于它们不同的激活特性，IAHP实现了改善低频信号峰电位频率编码的噪声整形，而IM实现了改善高频信号峰电位时间编码的高通滤波。
Spike frequency adaptation causes reduced spiking during prolonged stimulation, but the full impact of adaptation on neural coding is far more complex, especially if one takes into account the diversity of biophysical mechanisms mediating adaptation and the different ways in which neural information can be encoded. Here, we show that adaptation has opposite effects depending on the neural coding strategy and the biophysical mechanism responsible for adaptation. Under noisy conditions, calcium-activated K+ current (IAHP) improved efficient spike-rate coding at the expense of spike-time coding by regularizing the spike train elicited by slow or constant inputs; noise power was increased at high frequencies but reduced at low frequencies, consistent with noise shaping that improves coding of low frequency signals. In contrast, voltage-activated M-type K+ current (IM) improved spike-time coding at the expense of spike-rate coding by stopping the neuron from spiking repetitively to slow inputs so that it could generate isolated, well-timed spikes in response to fast inputs. Using dynamical systems analysis, we demonstrate how IAHP minimizes perturbation of the interspike interval caused by high frequency noise, whereas IM minimizes disruption of spike timing accuracy caused by repetitive spiking. The dichotomous outcomes are related directly to the distinct activation requirements for IAHP and IM, which in turn dictate whether those currents mediate negative feedback onto spiking or membrane potential. Thus, based on their distinct activation properties, IAHP implements noise shaping that improves spike-rate coding of low frequency signals whereas IM implements high-pass filtering that improves spike-time coding of high frequency signals.