The presence of a clearly modulated STA suggests that systematic phase relationships with spike times exist. Two example LFP traces with simultaneously recorded putative FSI spikes are shown in Figure 12A, and suggest a relationship between the phase of gamma oscillations and spike times. To quantify this effect, histograms over the phase of each spike relative to gamma-50 and gamma-80 were computed for each cell, and the preferred firing phase extracted by circular mean. (Example shown in Figure 12B; while this method of assessing phase preference, based on the length of the mean vector, does not deal with multimodal phase distributions, where e.g., two opposing modes of equal magnitude could cancel each other out; however, inspection of individual phase preference curves revealed no such patterns.) For both gamma-50 and gamma-80, the majority of FSIs showed a small but significant phase preference (Rayleigh's r, p < 0.001, corrected for multiple comparisons; 32/53 for gamma-50, 36/53 for gamma-80). Over all FSIs, the distributions of mean phase angles were significantly non-uniform (Rayleigh's r, p = 0.0093 and 0.0039 for gamma-50 and gamma-80 respectively,
