Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom.
Biophys J. 2013 Mar 5;104(5):1006-17. doi: 10.1016/j.bpj.2013.01.015.
Postsynaptic Ca(2+) transients triggered by neurotransmission at excitatory synapses are a key signaling step for the induction of synaptic plasticity and are typically recorded in tissue slices using two-photon fluorescence imaging with Ca(2+)-sensitive dyes. The signals generated are small with very low peak signal/noise ratios (pSNRs) that make detailed analysis problematic. Here, we implement a wavelet-based de-noising algorithm (PURE-LET) to enhance signal/noise ratio for Ca(2+) fluorescence transients evoked by single synaptic events under physiological conditions. Using simulated Ca(2+) transients with defined noise levels, we analyzed the ability of the PURE-LET algorithm to retrieve the underlying signal. Fitting single Ca(2+) transients with an exponential rise and decay model revealed a distortion of τ(rise) but improved accuracy and reliability of τ(decay) and peak amplitude after PURE-LET de-noising compared to raw signals. The PURE-LET de-noising algorithm also provided a ∼30-dB gain in pSNR compared to ∼16-dB pSNR gain after an optimized binomial filter. The higher pSNR provided by PURE-LET de-noising increased discrimination accuracy between successes and failures of synaptic transmission as measured by the occurrence of synaptic Ca(2+) transients by ∼20% relative to an optimized binomial filter. Furthermore, in comparison to binomial filter, no optimization of PURE-LET de-noising was required for reducing arbitrary bias. In conclusion, the de-noising of fluorescent Ca(2+) transients using PURE-LET enhances detection and characterization of Ca(2+) responses at central excitatory synapses.
突触后 Ca(2+) 瞬变是由兴奋性突触传递引发的关键信号步骤，用于诱导突触可塑性，通常在组织切片中使用双光子荧光成像和 Ca(2+) 敏感染料进行记录。产生的信号很小，峰值信噪比 (pSNR) 非常低，这使得详细分析变得困难。在这里，我们实施了一种基于小波的去噪算法 (PURE-LET)，以增强生理条件下单个突触事件引发的 Ca(2+) 荧光瞬变的信号/噪声比。使用具有定义噪声水平的模拟 Ca(2+) 瞬变，我们分析了 PURE-LET 算法恢复潜在信号的能力。用指数上升和下降模型拟合单个 Ca(2+) 瞬变，与原始信号相比，PURE-LET 去噪后 τ(rise)的拟合失真，但 τ(decay)和峰值幅度的拟合准确性和可靠性得到提高。与优化的二项式滤波器相比，PURE-LET 去噪算法还提供了约 30dB 的 pSNR 增益。与优化的二项式滤波器相比，PURE-LET 去噪提供的更高 pSNR 使突触传递成功和失败之间的区分准确性提高了约 20%，这是通过测量突触 Ca(2+) 瞬变的发生来衡量的。此外，与二项式滤波器相比，PURE-LET 去噪不需要进行任意偏置的优化。总之，使用 PURE-LET 对荧光 Ca(2+) 瞬变进行去噪可增强中枢兴奋性突触的 Ca(2+) 反应的检测和特征描述。
