Figure 3.

Phase resetting correction of LFPs. Steady LFP activity recorded 0.5 s after the 10 ms stimulus switched off look similar (A) and can be better overlapped by an appropriate circular shifting (B) that removes the waveform phase shift due to phase resetting induced by the same light stimulus arriving at different phases during the ongoing rhythm. (C) Without phase shifting to correct for the phase resetting, the correlations between the waveforms of different trials with respect to an arbitrarily selected “reference” trial are relatively small at an average of 0.0143 ± 0.055 (red trace). A significant improvement in pair correlation between trials occurs after appropriately shifting the waveforms to maximize the correlation coefficient (blue trace) with an average correlation of 0.5854 ± 0.1383. (D) Similar to correlation, the root-mean-square error between a trial and the corresponding “reference” trial significantly decreases. The rms error decreases form 13.4 ± 2.9 for correlation between trials without phase resetting correction (red line), to 8.5 ± 2.1 after phase-shifting all trials to correct for phase resetting (blue line), to 6.9 ± 1.8 for phase-shifted dendrogram-based correlation (green solid circles).