Fig 3. Memory performance improvement and phase-amplitude timing: SO phase at spindle peak was correlated with memory improvement in zolpidem and placebo conditions suggesting a general mechanism of memory formation.

This relationship was not observed in sodium oxybate, which showed the worst performance. Phase value of each subject corresponds to the average value over all spindle/SO complexes in that subject. (a): All conditions, (b): zolpidem, (c): placebo (d): sodium oxybate.