Fig. 4.

Ripple-triggered replay. a Grand average of ripples and ripple-triggered raw EEG traces in the hippocampus. Time 0 indicates the onset of ripple events. b Examples of individual ripple events in four patients (highpass filtered at 5 Hz for display purposes). The blue line marks the duration of ripple events. c Analysis of replay during ripple events and peri-ripple periods: schematic overview. Top: Example of intracranial EEG activity from the hippocampus (highpass filtered at 40 Hz). Below: time windows used to extract activity during peri-ripple periods and ripple events. d Time resolved replay of gamma activity locked to ripples during nREM sleep and waking state for later remembered and forgotten remote items. Ripple time 0 corresponds to ripple events and ripple time before and after 0 correspond to peri-ripple period. The early and the late cluster correspond to the stimulus-specific clusters in Fig. 2a. e Ripple-triggered replay of early and late encoding activity differentially affects memory: Interaction between replay levels of remembered and forgotten items and gamma band activity from the early (100–500 ms) and the late (500–1200 ms) encoding clusters. f Direct comparisons of replay levels during ripple events between later remembered and later forgotten remote items. Each colorful dot indicates one participant. Same colors indicate data from the same participant. Error bars, standard error of the mean; *p < 0.05 (paired t test); **p < 0.01 (2 × 2 repeated measures ANOVA); X, p = 0.071 (paired t test); time windows showing higher replay levels for remembered vs. forgotten items during ripple events are indicated by gray background