Code for Quantitative and Qualitative Analysis of Phase Shift of Recorded Local Field Potential

Assess phase shift of local field potential (LFP) visually and quantitatively in degrees.

This code allows the user to assess phase shift of local field potential (LFP) in two ways. It depicts the intensity of the LFP recorded by channels 4, 8, 12, 16, 20, 24, 28, and 32 on a colormap - allowing the viewer to visually assess phase shift based upon the gradual longitudinal transposition of the crests and troughs of the waveform as represented by high and low intensity colors on the colormap. It then quantitatively assess phase shift between channels 1 and 32 by first down-sampling the raw LFP to 2034.505Hz and utilizing a second-order Butterworth filter and then a zero-phase digital filter in the forward and reverse directions in order to smooth the data and negate any changes to phase offset as a result of applying that filter. Then the absolute difference of the angular phase of the signal is quantified between the signals recorded from channel 1 and channel 32 at the same time point, for each time point. These absolute differences are summed and averaged - yielding the mean phase offset between the filtered LFP recorded from channel 1 and 32 over the course of the recording session.