a,b, Two vIRt units with “slow” rhythmic activity patterns. Top: breathing trace. Middle: Vibrissa angle and midpoint traces. Bottom: raster plot of spiking events (protraction phases shown in beige). c, Top: vibrissa trace and raster plot for a retraction unit. Bottom: Time-frequency spectrum of that spiking activity. The transition to rhythmic bursting appears as a high power frequency band, corresponding to whisking frequency. d, Same as c, for a “slow” oscillation unit. Here the transition to whisking shows a low frequency band, similar to vibrissa midpoint variations or breathing rhythm. e, Left: Time-frequency spiking spectrum for a retraction unit, averaged over all whisking bouts. Right: Inter-spike interval histograms for that retraction unit. Red, overall ISI. Blue, ISI during long whisking bouts. The ISI distribution becomes bimodal, with a strong peak at short interval corresponding to bursts. f, same as e, for a “slow” oscillation unit.