001). Nonetheless, relative gamma phase was more correlated with distance between place field peaks than the relative spike timing (Figure 8E; bootstrap resampling; Spearman ρ = gamma > time p < 0.05). Thus, as we observed for awake SWRs, gamma oscillations during Selleckchem Doxorubicin quiescent SWRs coherently modulates the hippocampal circuit and could act as an internal clock to synchronize the replay of stored memories. Finally we asked whether the strength of gamma synchrony during quiescent SWRs in the rest

session was correlated with the presence of replay. In contrast to our results for awake SWRs, we found no significant relationship between the increase in gamma synchrony during quiescent SWRs and the presence of significant replay (permutation test; significant > nonsignificant SWRs; coherence, p > 0.2; phase

locking, p > 0.2). This may be a result of the smaller increases in gamma synchrony during quiescent SWRs www.selleckchem.com/products/i-bet151-gsk1210151a.html and the overall lower fidelity of quiescent replay. We examined SWRs in awake and quiescent states and found a prominent and consistent increase in slow gamma power. During SWRs, gamma oscillations in CA3 and CA1 became more coherent both within and across hemispheres, indicating a transient synchronization of the entire dorsal hippocampal network. CA3 and CA1 neurons were phase locked to a common gamma rhythm during SWRs and gamma phase was a good descriptor of pairwise reactivation. Further, during awake SWRs, higher levels of gamma synchrony between CA3 and CA1 were associated with high fidelity replay of past experience. These results

suggest that gamma oscillations maintain the temporal organization of spiking during the reactivation of stored memories in the hippocampal network. Our results also revealed differences between awake and quiescent SWRs that may be related to the lower fidelity of replay seen during quiescence (Karlsson and Frank, 2009; Dupret et al., 2010). There were smaller increases in gamma synchrony during quiescent SWRs, a difference that could be largely attributed to the higher baseline levels of synchrony. Further, as compared to awake SWRs, spiking was less modulated by gamma oscillations during quiescent SWRs and we found no clear relationship between gamma Metalloexopeptidase synchrony and the fidelity of quiescent replay. These findings indicate that transitions from relatively uncoupled to highly coupled network states could be important for high fidelity memory replay. Our results are consistent with previous studies of slow gamma oscillations occurring outside of SWRs. Theoretical work has shown that gamma rhythms are well suited to synchronize networks with relatively low conduction delays (Kopell et al., 2000). Gamma rhythms have also been shown to improve information transmission in cortical networks (Sohal et al., 2009), consistent with our observation that gamma synchrony correlates with the presence of significant awake replay.