35%, n = 104 events) were theta independent. In contrast to the prefrontal NG, the phase coupling between hippocampal theta and gamma is absent at this age (Figure S3Bii). As for the adult Hipp (Buzsáki et al., 1992 and Le Van Quyen et al., 2008), the low amplitude (∼25 μV) neonatal ripples appeared in conjunction

with SPWs, are restricted to the Str pyr, and are tightly coupled to MUA discharge (Figure S3C). Similar to neocortical areas, hippocampal activity switched from discontinuous bursts to continuous theta rhythms during early postnatal development (n = 6 pups) (Figure S3D; selleck chemicals llc Table S3). However, this transition occurred 1–2 days earlier in the Hipp than in the PFC (Figure S4) and may reflect the differences in the maturation of cytoarchitecture and connectivity (Angevine, 1975). Several approaches OTX015 price were used to characterize the interactions between prefrontal and hippocampal activity during the first two postnatal weeks. First, we examined the temporal correspondence of discontinuous oscillations

across the PFC and CA1 area of the intermediate Hipp in simultaneous recordings from both areas. The majority of hippocampal theta bursts occurred within a narrow time window (<3 s) with SB or NG in the Cg (87.7%, n = 203 events from 6 pups) or PL (93.6%, n = 296 events from 9 pups) (Figure 4A), their onset either preceding (Cg: 20.7% of events, delay 0.5 ± 0.006 s, PL: 13.9% of events, delay 1 ± 0.14 s), succeeding (Cg: 3.9% of events, delay 0.14 ± 0.05 s, PL: 3.4% of events, delay 0.63 ± 0.24 s) or matching Calpain (Cg: 63.1% of events, PL: 73.4% of events) the onset of prefrontal events. Second, the temporal synchrony between hippocampal and prefrontal activity was assessed by spectral coherence analysis (Figures 4B and S5A). Due to the predominance of distinct activity patterns with different spatial organization in the Cg and PL, we separately analyzed the cingulate-hippocampal and the prelimbic-hippocampal synchronization. Coherence coefficients for simultaneously occurring oscillations in the Cg and Hipp (0.52 ± 0.02, n = 59 events from 6 pups) as well as

in the PL and Hipp (0.53 ± 0.02, n = 90 events from 9 pups) were relatively high. To decide whether the strong prefrontal-hippocampal coupling was restricted to simultaneously occurring oscillatory events, the coherence analysis was performed also for oscillations at shuffled time windows. The resulting coherence coefficients (Cg: 0.39 ± 0.02, n = 59 events from 6 pups, PL: 0.47 ± 0.002, n = 90 events from 9 pups) were significantly lower than for original time windows of oscillatory activity. To verify that this high level of coherence was a genuine feature of the prefrontal-hippocampal interactions, we additionally assessed the synchronization between the Hipp and V1 as well as between different neocortical areas. The level of coherence for oscillatory events in the CA1 area and V1 was significantly (p < 0.01) lower (0.37 ± 0.

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