Research About Response Characteristics Of Local Field Potential Based On Hilbert-Huang Transform

The primary visual cortex is the first station of visual processing mechanism in cerebral cortex, and it is significance to in-depth analysis of response characteristics of signals for study visual processing mechanism in primary visual cortex. Most of the researches were based on the activity potential (spike) and local filed potential (LFP) recorded from primary visual cortex. However spike is susceptible to noise interference when it was detected, which resulting in missed and false detection, and the subsequent analysis was affected seriously. Therefore, research of response characteristics based on LFP was gradually studied by researchers. Studied have shown that visual stimulation was encoded by LFP, however, no coherent conclusion exists about which frequency ranges exhibit feature tuning. Extracting of response ranges of LFP has far-reaching significance to study visual processing mechanism.Addressing this, the response characteristic frequency bands of LFP which is non-stationary signal were extracted based on Hilbert-Huang Transform (HHT) in this paper, and response tuning characteristics underlying the stimuli of spatial frequency and orientation were researched, and wavelet transform was compared. The main contents are as follows:1. Signal acquisition and signal analysis. Spike and LFP signal were collected and recorded from anaesthetic Long Evans rat, and the characteristics of LFP and analysis methods used commonly were expounded, which laid the foundation for the study of tuning characteristics of LFP.2. Response characteristics of local field potential based on wavelet transform was researched. We studied the response characteristics for spatial frequency and orientation according to the Gamma band of LFP which extracted by wavelet decomposition, and the spike recorded from the same electrode was compared. The results showed that the Gamma band reflected different response to different visual stimuli, and it was consistent with spike. However, wavelet transform depends on the choice of the wavelet function which is the difficulties and disadvantages of wavelet transform analysis. 3. Response characteristics of local field potential based on Hilbert-Huang transform was researched. In contrast to previous studies, which often reported correlates of visual processing only in a limited frequency range of LFP, here the entire frequency range of LFP were studied by HHT in visual processing. The response characteristics for spatial frequency and orientation were studied based on the intrinsic mode functions of LFP which decomposed by HHT. The results showed that the second intrinsic mode function reflected response to visual stimuli compared with the other intrinsic mode functions, and it was consistent with spike. The method avoids the trouble of the wavelet transform which requires a proper wavelet basis, and a more accurate response characteristic was obtained, providing an effective means for feature extraction and the follow-up study of LFP, and it has a high value of promotion.4. The tuning characteristics of LFP underlying the stimuli of spatial frequency and orientation based on wavelet transform and HHT was compared. The results showed that the average tuning index obtained from HHT is higher than wavelet transform. Therefore, extracting response band of LFP based on HHT is more advantages.