Under natural visual stimulation (movies) in anesthetized monkeys, for band-passed LFPs in a given frequency range (y axis, in 4-Hz-wide nonoverlapping intervals), the LFP phase at any fixed time during the movie fluctuates from trial to trial, and this phase (un)reliability of V1 LFPs was assessed by the circular variance across trials (defined between 0 (total reliability) and 1 (total unreliability). It is plotted as function of the spike rate in the corresponding window, since the reliable phase values must be observed during periods of firing in order to be useful for phase-of-spiking stimulus coding. Phase coding is reliable if the circular variance is small; this is the case only at low frequencies (a few hertz). Reproduced with permission from [693].