EEG spindle density, slow-oscillation density and slow oscillation-associated theta activity during non-REM sleep are related to pattern separation performance. a, b, Correlation between PatSep performance and spindle density (a; n = 12) and slow oscillation density (b; n = 13) during non-REM sleep (SWS and S2, recordings from C3/C4). c, Correlation between PatSep performance and phase-locked theta (4–8 Hz) power (at C3) during slow oscillation (i.e., in a −0.5 to 0.25 s window around the negative slow oscillation peak; n = 12). Slow oscillations were identified in non-REM sleep (SWS and S2). d, Averaged time–frequency plot of EEG wavelet power during slow oscillations (at C3) in a ±1.5 s time window around the negative slow oscillation peak (0 s) for a 2–24 Hz frequency band (n = 12).