Department of Neuroscience, University College London, UK.
Neuroimage. 2010 Mar;50(1):99-111. doi: 10.1016/j.neuroimage.2009.12.010. Epub 2009 Dec 11.
Brief radiant laser pulses can be used to activate cutaneous Adelta and C nociceptors selectively and elicit a number of transient brain responses in the ongoing EEG (N1, N2 and P2 waves of laser-evoked brain potentials, LEPs). Despite its physiological and clinical relevance, the early-latency N1 wave of LEPs is often difficult to measure reliably, because of its small signal-to-noise ratio (SNR), thus producing unavoidable biases in the interpretation of the results. Here, we aimed to develop a method to enhance the SNR of the N1 wave and measure its peak latency and amplitude in both average and single-trial waveforms. We obtained four main findings. First, we suggest that the N1 wave can be better detected using a central-frontal montage (Cc-Fz), as compared to the recommended temporal-frontal montage (Tc-Fz). Second, we show that the N1 wave is optimally detected when the neural activities underlying the N2 wave, which interfere with the scalp expression of the N1 wave, are preliminary isolated and removed using independent component analysis (ICA). Third, we show that after these N2-related activities are removed, the SNR of the N1 wave can be further enhanced using a novel approach based on wavelet filtering. Fourth, we provide quantitative evidence that a multiple linear regression approach can be applied to these filtered waveforms to obtain an automatic, reliable and unbiased estimate of the peak latency and amplitude of the N1 wave, both in average and single-trial waveforms.
简短的放射状激光脉冲可以选择性地激活皮肤的 Adelta 和 C 伤害感受器，并在持续的脑电图（激光诱发脑电位的 N1、N2 和 P2 波，LEP）中引起许多瞬态脑反应。尽管它具有生理和临床相关性，但 LEP 的早期潜伏期 N1 波由于其信噪比（SNR）较小，因此通常难以可靠地测量，从而对结果的解释产生不可避免的偏差。在这里，我们旨在开发一种方法来提高 N1 波的 SNR，并测量其在平均和单次试验波形中的峰值潜伏期和幅度。我们得出了四个主要发现。首先，我们建议使用中央-额导联（Cc-Fz）比推荐的颞-额导联（Tc-Fz）更好地检测 N1 波。其次，我们表明，当使用独立成分分析（ICA）初步分离和去除干扰 N1 波头皮表达的 N2 波下的神经活动时，可以最佳地检测到 N1 波。第三，我们表明，在去除这些与 N2 相关的活动后，可以使用基于小波滤波的新方法进一步提高 N1 波的 SNR。第四，我们提供定量证据表明，可以将多元线性回归方法应用于这些滤波后的波形，以获得 N1 波的峰值潜伏期和幅度的自动、可靠和无偏估计值，无论是在平均还是单次试验波形中。
