Fig. 2.

Cortico-cortical and hippocampo-cortical ripples couple and co-occur during waking and NREM. (A) Cross-correlograms of ripples between all possible cortical sites reveals strong ripple coupling (occurring within 500 ms of each other without necessarily overlapping) between nearly all sites during NREM (n = 4,487/4,550 significant channel pairs) and waking (n = 4,478/4,550; post-FDR P < 0.05, randomization test). Dashed lines show 99% confidence interval of the null distribution (200 shuffles per channel pair). (B) Same as A except cross-correlograms of hippocampal ripples relative to cortical ripples (NREM: n = 133/461; waking: n = 401/461). (C) Conditional co-occurrence probabilities of cortico-cortical and hippocampo-cortical ripples overlapping for at least 25 ms (i.e., probability of a ripple in a particular channel given a ripple in another particular channel) are greater during waking than NREM (****post-FDR P < 0.0001, two-sided paired t test). (D) Observed over chance cortical ripple co-occurrence (logarithmic scale) increases with the number of sites corippling. (E) Cortical ripple co-occurrence probabilities during NREM are stable with increasing intervening fiber tract distance (linear mixed effects with patient as random effect). Dashed line indicates chance. When two channels were in the same parcel the fiber tract distance was defined as 0. (F) Same as E except for waking. Fit is linear least-squares regression. Error shows SEM.