Orientation Selectivity Analysis Of Macaque Based On Gamma-band Local Field Potential

Orientation selectivity plays an important role in the process of visual neural coding.Neurons in V1 and V4 of the visual cortex show a certain orientation selectivity,but the formation mechanism of orientation selectivity is not clear.Local field potential(LFP)is the low-frequency part of the neural signal in the area near the electrode tip,and it has relatively rich neural information.In this paper,the implanted microelectrode array is used to collect the LFP in V1 and V4 of the macaque visual cortex,and the related features of Gamma-band LFP are analyzed under different orientation stimuli.It is of great significance to explore the formation mechanism of neuronal orientation selectivity.First of all,the phase randomized and thresholded wavelet bicoherence is used to analyze the quadratic phase coupling(QPC)of Gamma-band LFP in the V1 and V4 under sinusoidal grating stimulation,and the total bicoherence(Total Bic)is used to quantify the overall QPC of the Gamma-band LFP.It is found that there is a strong correlation between Total Bic and the grating orientations.In addition,The Gamma-band LFP in V1 modulates the QPC in V4.Taken together,the QPC can reflect the characteristics of visual stimulation in different orientations,and describes the interaction of Gamma-band LFP between different brain regions.Secondly,the Hilbert-huang spectral entropy and energy spectral entropy of the Gamma-band LFP in V1 and V4 under different orientation gratings are calculated,and it is found that they would change regularly with the changes in grating orientation.The circular statistic is used to quantify the orientation tuning curves of the Hilbert-huang spectral entropy,energy spectral entropy and the spike firing rate.The results show that Hilbert-huang spectral entropy and energy spectral entropy are more sensitive to grating stimulation.In order to dig deeper into the performance of these three methods in the analysis of orientation selectivity,the relative variation coefficients of the Hilbert-huang spectral entropy,energy spectral entropy and spike firing rate under different signal-to-noise ratios are calculated.It is found that the Hilbert-huang spectral entropy has better noise immunity.Finally,the coherence,the phase locking value and the global synchronization are used to analyze the synchronization of Gamma-band LFP between V1 and V4 under sinusoidal grating stimulation.It is found that the grating has modulation effect on synchronization between V1 and V4 and the overall synchronization in V1 and V4.Through calculating its orientation tuning indexes,it is found that the coherence can better characterize the synchronization between V1 and V4 than the phase locking value.Compared with the global frequency domain synchronization,the global phase synchronization can better characterize the overall synchronization in V1 and V4.