A Study Of Coding Stimulus Via PCA Eigenvalue Of Multichannel LFPs

[Objective]We performed PCA method to multichannel local field potentials(LFPs),aims to make research on coding the pattern of LFPs synchronization under positive stimulus and negative stimulus.[Methods](1) PCA of LFPs synchronization:This thesis carries on synchronization pattern analysis on 14-channel LFPs under positive stimulus and a negative stimulus,by application of PCA method of correlation matrix,using the max eigenvalueλ₁ as a index.Select bin width as 50ms,with 25ms step-in,calculate the Pearson correlation of each channels,construct these correlation coefficients to a correlation matrix,then calculate the eigenvalues of matrix.Select Daubechies db4 wavelet as wavelet basis function,and the length of dissolution L was decided as 8 according to the sampling frequency of LFPs.Then the scope of the disillusion frequency are:fifth length is to 30-60Hz,which corresponding to main frequency scope of y frequency band,and eigth length is to 4-8Hz,which corresponding to 0 frequency band.(2) PCA of LFPs phase synchronization:To make phase synchronization pattern analysis on the 14-channel LFPs,Hilbert transform was applied to count the phase position of each channel of LFPs,then take the same steps as as(1) does to work out the max eigenvalueλ₁ of correlation matrix of LFPs phase on three frequency bands. The results ofλ₁ are showed as dynamic map and histogram.The research data applied on this thesis were provided by Institute of Neurobiology,Fudan University,Shanghai,China,including two groups,one group is 16-channel LFPs under negative stimulus,the other group is 16-channel LFPs under positive stimulus,each group includes 10 experiments data.Preprocess 16-channel LFPs and get well recorded 14-channel LFPs.[Results](1) The relult of LFPs synchronization: ①λ₁ is(0.56±0.13) after positive stimulus and(0.42±0.10) before the positive stimulus(P<0.05).Under negative stimulus,λ₁ is(0.42±0.09) after stimulus and (0.41±0.10) before it.â‘¡Onθfrequency band,λ₁ is(0.64±0.18) after positive stimulus and(0.41±0.12) before positive stimulus(P<0.01).Under negative stimulus,λ₁ is(0.40±0.12) after stimulus and(0.39±0.12) before it.â‘¢On y frequency band,λ₁ is(0.60±0.13) in after conditional stimulus and (0.43±0.10) before stimulus(P<0.05).Under negative stimulus,λ₁ is (0.48±0.09) after stimulus and(0.46±0.10) before it.(2) The relult of LFPs phase synchronization:①λ₁ is(0.39±0.09) after positive stimulus and(0.27±0.08) before positive stimulus(P<0.05).Under negative stimulus,λ₁ is(0.31±0.08) after stimulus and (0.29±0.09) before it.â‘¡Onθfrequency band,λ₁ is(0.50±0.17) after positive stimulus and(0.30±0.11) before stimulus(P<0.01).Under negative stimulus,λ₁ is(0.30±0.11) after stimulus and(0.29±0.11) before it.â‘¢Onγfrequency band,λ₁ is(0.48±0.11) after positive stimulus and(0.35±0.08) before positive stimulus(P<0.05).Under negative stimulus,λ₁ is(0.36±0.08) after stimulus and(0.35±0.09) before it.[Conclusions]It is found through analysis of PCA of LFPs synchronization and LFPs phase synchronization thatλ₁ can representative the coding of LFPs to the positive stimulus, and that synchrony of LFPs after positive stimulus is obvious higher than that of LFPs before positive stimulus.Under negative stimulus,there is not much difference betweenλ₁ of after stimulus and that of before stimulus(P>0.05).While under positive stimulus,λ₁ of after stimulus is much higher than that of before stimulus(P<0.05).