多通道局部场电位时变频谱的同步模式及其对行为事件的编码

Time-Varying Spectrum Synchronous Pattern and Behavior-Event Encoding by Multi-Channel Local Field Potentials

用时变相干(time-varying coherence)频谱方法分析多通道局部场电位(local field potentials,LFPs)随时间变化的同步模式及其对行为事件的编码。实验数据为行为事件前后3秒的28通道LFPs。分别计算每个通道LFP的功率谱密度(power spectral density,PSD)及多通道LFPs各个特征频段的PSD,选取PSD分布集中的θ频段为LFPs的特征频段;应用离散二进小波变换获取LFPs的θ频段分量;从28通道LFPs中选取PSD最大的通道作为参考通道。选取计算窗口为50ms,从初始点开始计算每个窗口中每个通道LFP及其θ分量对参考通道的频谱相干分析。移动窗口步长为25ms,获取多通道LFPs及其θ分量的时变频谱相干动态分布。研究结果显示,θ频段分量的PSD占LFPs总功率的71.95%,表明θ分量是实验中多通道LFPs同步的特征频段;多通道LFPs的θ分量频谱相干值随时间变化,行为事件点前后1s的相干值具有显著差别(P<0.05),表明多通道LFPs的θ频段时变频谱相干有效地编码了这一行为事件。

This study developed time-varying spectrum coherence to analyze time-dependent synchronization pattern and coding to event among multi-channel local field potentials （LFPs）. Experiment data were 28-channel LFPs related to the event ± 3 s. Power spectral density （PSD） on each channel LFP and every characteristic frequency band of multi-channel LFPs was performed for spectrum power respectively. Characteristic bandwidth as theta-band power was acquired by selecting PSD distributed intensively. And then discrete dyadic wavelet transformation was applied for separating theta-band LFPs. After choosing the reference channel LFP which had the largest PSD value, spectrum coherence was calculated in each window between each channel LFP and reference channel LFP with 50 ms multi-taper window sliding from the beginning. Time-varying spectrum coherence dynamic distribution was available between each channel LFP and reference channel LFP with 25 ms overlapping, and the theta band component LFP as well. The results show that the PSD on theta band component LFP occupied for 71.95% in total power of LFPs, indicating theta-band is the characteristic band of multi-channel LFPs in this paper. Spectrum coherence of theta-band LFPs was time-dependent and increased at the onset of the event ± 1 s significantly （P〈0.05）, indicating the time-varying coherence on characteristic bandwidth of multi-channel LFPs encodes the event effectively.