Sensitivity to perturbations in vivo implies high noise and suggests rate coding in cortex.
Sensitivity to perturbations in vivo implies high noise and suggests rate coding in cortex.
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作者：
众所周知，神经活动表现出变异性，即相同的感官刺激产生不同的反应，但很难确定这种变异性意味着什么。它是噪音，还是携带着重要的信息--例如，关于有机体的内部状态？我们从下而上解决这个问题，通过询问皮质网络活动的小扰动是否被放大。基于在大鼠桶皮质的体内全细胞记录，我们发现，一个神经元中的一个单一的额外的尖峰组成的扰动产生约28个额外的尖峰在其突触后的目标，我们表明，使用同时的细胞内和细胞外的记录，一个单一的尖峰产生一个可检测的增加在本地网络的放电率。理论分析表明，这种放大导致膜电位的内在的、不依赖于刺激的变化，其量级为±2.2 - 4.5 mV，这些变化是纯噪声，因此根本不携带任何信息。因此，要让大脑执行可靠的计算，它必须使用速率代码，或者产生非常大的快速去极化事件，例如synfire链理论提出的事件-但在我们的体内记录中，我们发现这样的事件非常罕见。我们的研究结果与大脑皮层可能主要使用速率编码的观点一致。
It is well known that neural activity exhibits variability, in the sense that identical sensory stimuli produce different responses, but it has been difficult to determine what this variability means. Is it noise, or does it carry important information – about, for example, the internal state of the organism? We address this issue from the bottom up, by asking whether small perturbations to activity in cortical networks are amplified. Based on in vivo whole-cell recordings in rat barrel cortex, we find that a perturbation consisting of a single extra spike in one neuron produces ~28 additional spikes in its postsynaptic targets, and we show, using simultaneous intra- and extra-cellular recordings, that a single spike produces a detectable increase in firing rate in the local network. Theoretical analysis indicates that this amplification leads to intrinsic, stimulus-independent variations in membrane potential on the order of ±2.2 - 4.5 mV – variations that are pure noise, and so carry no information at all. Therefore, for the brain to perform reliable computations, it must either use a rate code, or generate very large, fast depolarizing events, such as those proposed by the theory of synfire chains – yet in our in vivo recordings, we found that such events were very rare. Our findings are consistent with the idea that cortex is likely to use primarily a rate code.
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DOI：
10.1073/pnas.0712231105
发表时间：
2008-03-04
影响因子：
11.1
作者：
Izhikevich, Eugene M.;Edelman, Gerald M.
通讯作者：
Edelman, Gerald M.
影响因子：
16.2
作者：
Mainen, ZF;Joerges, J;Sejnowski, TJ
通讯作者：
Sejnowski, TJ
影响因子：
1.2
作者：
Herrmann, A;Gerstner, W
通讯作者：
Gerstner, W
影响因子：
2.5
作者：
Latham, PE;Richmond, BJ;Nirenberg, S
通讯作者：
Nirenberg, S
影响因子：
5.5
作者：
Holmgren, C;Harkany, T;Zilberter, Y
通讯作者：
Zilberter, Y