Averaged oscillatory responses to words presented during N2 and SWS in the time–frequency spectrum recorded at all frontal channels (F3, F4, Fz, F7, and F8) for memory-independent and memory-dependent processes. (A) Oscillatory power changes to all words presented during N2 and SWS show characteristic increases in the delta, theta, and alpha bands, followed by increases in the spindle and beta bands. (B) Oscillatory responses to all words presented in N2. (C) Oscillatory responses to all words presented during SWS. (D) Difference between the neural responses of all words in N2 and SWS. Responses in all different frequency bands were more pronounced after word presentations during N2 than in SWS (see the text for significant clusters). (E) For memory-dependent oscillatory processes, we did not observe any significant cluster when comparing oscillatory responses for all remembered words irrespective of the sleep stages when words were presented. (F) Similarly, there was no difference between the oscillatory responses of all remembered and nonremembered words during N2. (G) Also, there was no significant difference between the neural responses of all remembered and nonremembered words during SWS. (H) Consistently, we could not detect any significant increase or decrease between memory-dependent oscillatory processes after reactivation in N2 versus SWS.
