Improved spike inference accuracy by estimating the peak amplitude of unitary [Ca2+] transients in weakly GCaMP6f-expressing hippocampal pyramidal cells
Improved spike inference accuracy by estimating the peak amplitude of unitary [Ca2+] transients in weakly GCaMP6f-expressing hippocampal pyramidal cells
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DOI：
10.1113/jp277681
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发表时间：
2019-06-01
影响因子：
5.5
通讯作者：
Nusser, Zoltan
中科院分区：
文献类型：
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作者：
Eltes, Timea;Szoboszlay, Miklos;Nusser, Zoltan
要点单一的单动作电位诱发的[Ca~(2+)]瞬变的幅度与GCaMP6f的表达呈负相关，但在表达水平相似的海马锥体细胞中表现出很大的差异性。荧光信号的总和是频率相关的、超线性的，并且还表现出显著的细胞到细胞的变异性。脉冲推断误差的主要来源是峰值幅度的变异性，而不是衰减或超线性。我们开发了两种方法来估计单一[Ca~(2+)]瞬变的峰值幅度，并表明在弱表达GCaMP6f的细胞中，使用这些单一幅度估计对MLSpike进行的尖峰干扰导致类似5%的错误率。使用遗传编码的钙离子指示器研究行为动物的神经元活动受到来自荧光示踪剂的尖峰电流推断的不准确性的阻碍。在这里，我们将双光子[Ca~(2+)]成像与细胞附着记录相结合，随后对GCaMP6f的表达水平进行事后测定，以探索它如何影响小鼠海马锥体细胞(PC)体细胞[Ca~(2+)]瞬变的幅度、动力学和时间总和。单一[Ca~(2+)]瞬变的幅度(由单个动作电位诱发)与GCaMP6f的表达呈负相关，但即使在表达水平类似低的PC之间也显示出很大的变异性。荧光信号的总和是频率相关的、超线性的，并且还表现出显著的细胞到细胞的变异性。我们进行了基于数据的实验模拟，发现使用MLSpike的棘波推断错误率强烈依赖于单一峰值幅度和GCaMP6f表达水平。我们提供了简单的方法来估计单个弱表达GCaMP6f的PC中的单一[Ca~(2+)]瞬变，使用该方法，我们获得了类似于5%的尖峰推断错误率。
Key pointsThe amplitude of unitary, single action potential-evoked [Ca2+] transients negatively correlates with GCaMP6f expression, but displays large variability among hippocampal pyramidal cells with similarly low expression levels. The summation of fluorescence signals is frequency-dependent, supralinear and also shows remarkable cell-to-cell variability. The main source of spike inference error is variability in the peak amplitude, and not in the decay or supralinearity. We developed two procedures to estimate the peak amplitudes of unitary [Ca2+] transients and show that spike inference performed with MLspike using these unitary amplitude estimates in weakly GCaMP6f-expressing cells results in error rates of similar to 5%. Investigating neuronal activity using genetically encoded Ca2+ indicators in behaving animals is hampered by inaccuracies in spike inference from fluorescent tracers. Here we combine two-photon [Ca2+] imaging with cell-attached recordings, followed by post hoc determination of the expression level of GCaMP6f, to explore how it affects the amplitude, kinetics and temporal summation of somatic [Ca2+] transients in mouse hippocampal pyramidal cells (PCs). The amplitude of unitary [Ca2+] transients (evoked by a single action potential) negatively correlates with GCaMP6f expression, but displays large variability even among PCs with similarly low expression levels. The summation of fluorescence signals is frequency-dependent, supralinear and also shows remarkable cell-to-cell variability. We performed experimental data-based simulations and found that spike inference error rates using MLspike depend strongly on unitary peak amplitudes and GCaMP6f expression levels. We provide simple methods for estimating the unitary [Ca2+] transients in individual weakly GCaMP6f-expressing PCs, with which we achieve spike inference error rates of similar to 5%.