A Study Of Coding Stimulus Via Phase Synchronization Pattern Of Multi-channel Local Field Potentials And Its θ Component

[Objective]One of the important interaction modes in brain is oscillatory activity at different levels of neuronal activity.Neuronal oscillations can encode outside information (stimulus) by expressing and transferring the information(stimulus).Local field potentials(LFPs) represent a running average of all of the dendritic activities surrounding the implanted electrode and display the "signature" oscillatory properties of intergrated neuronal activity.The major focus of the current study is how the phase synchronization pattern of 16-channel LFPs in cognitive cortex of experiment animal encodes the positive stimulus.This study can provide evidence for exploring phase synchronization oscillatory pattern of multi-channel LFPs.[Methods]1.Experimental recordings:The electrophysiological activity was collected by Institute of Brain Science in Fudan University;2.Original recordings preprocessing:The 16-channel LFPs were obtained by band-passing the original electrophysiological activity signal(0.5～300Hz). 14-channel LFPs were left after zero-mean preprocessing and eliminating two-channel bad recordings;3.Instantaneous phase extraction of 14-channel LFPs:The method of instantaneous phase extraction was the commonly used Hilbert transform;4.Obtaining different rhythm wavelet components:Wavelet components in different rhythms were decomposed by wavelet transform;5.Selecting a reference channel:The reference channel is of the fastest average firing rate in all channels;6.Sliding window and step parameter:The length of sliding widow is 50ms and step is 25ms;7.The synchronous phase activity of 14-channel LFPs and different rhythm wavelet components:These were obtained by calculating cross-correlation measure between the reference channel and other channels.[Results]This study has investigated how the synchronous phase activity of 14-channel LFPs and different rhythms wavelet components encodes the stimulus.The following data are results: 1.Positive stimulus condition:①before and after stimulus point:the phase synchronization pattern of 14-channel LFPs has statistical significance(P<0.05).mean of LFPs phase synchronization: before:0.1974±0.0975 after:0.4090±0.1660②before and after stimulus point:the phase synchronization pattern ofθband has significant difference(P<0.001),the phase synchronization pattern of other bands of 14-channel LFPs have no statistical significance(P>0.05).mean of LFPs phase synchronization ofδ,θ,α,β,γband:θrhythm:before:0.2760±0.1913 after:0.7454±0.32462.Negative stimulus condition:①before and after stimulus point:the phase synchronization pattern of 14-channel LFPs has no statistical significance(P>0.05).mean of LFPs phase synchronization: before:0.3528±0.0828 after:0.3085±0.1540②before and after stimulus point:all the phase synchronization pattern of different rhythm wavelet components of 14-channel LFPs have no statistical significance(P>0.05).mean of LFPs phase synchronization ofδ,θ,α,β,γband:θrhythm:before:0.4198±0.1573 after:0.3783±0.1715[Conclusions]This study has investigated how the phase synchronization pattern of 14-channel LFPs and different rhythm wavelet components encodes the stimulus.The results show that:(1) The phase synchronization pattern of 14-channel LFPs and different rhythm wavelet components under negative stimulus condition has no statistical significance;(2) The phase synchronization degree of 14-channel LFPs and itsθband wavelet component increased significantly after positive stimulus and has statistical significance;(3) The phase synchronization pattern of other rhythm wavelet components of 14-channel LFPs after positive stimulus have no statistical significance.So the phase synchronization oscillation pattern of 14-channel LFPs, especiallyθwavelet component can encode the positive stimulus.