The majority of cingulate SB appeared widely synchronized, whereas the relative low occurrence of NG precluded a consistent analysis of their coupling over the Cg. In the PL, most of SB (720 out
of 1200) were also widely synchronized, while the majority of prelimbic NG (768 out of 1472) synchronized the upper layers and the cortical plate (CP) (Figure 3D). The distinct spatial organization, current generators, and synchronization patterns of SB and selleckchem NG argue for different oscillatory entrainment of cingulate and prelimbic networks during neonatal development. This distinction persisted also at prejuvenile age, since the amplitude and main frequency of continuous theta-gamma rhythms in P10–14 rats (n = 19) differed significantly between the Cg and PL. Moreover, the power of superimposed gamma episodes was significantly (p < 0.001) higher in the PL (2737 ± 109 μV2/Hz, n = 19 pups) than in the Cg (2646 ± 110 μV2/Hz). The distinct properties of discontinuous versus continuous prefrontal oscillations suggest that the networks entrained for their generation are subject of intense
refinement and reorganization during postnatal development. In the light of the recently demonstrated function of hippocampal theta to temporally coordinate the prefrontal activity at adulthood (Siapas et al., 2005 and Sirota et al., 2008) the question arises, when during development the hippocampal control Vemurafenib mw over the PFC emerges. The premise for addressing this question was to characterize in neonatal and prejuvenile rats (n = 33) the activity of the CA1 area of the intermediate Hipp, which at adulthood is known to densely project to the PFC (Hoover and Vertes, Casein kinase 1 2007). Already at birth prominent sharp-waves (SPWs) (Table S3; Figure S3A), which reversed across the pyramidal layer (Str pyr) and were accompanied by strong MUA discharge (13.07 ± 3.51 Hz, n = 10 pups), were present in the CA1 area. From P1
on, discontinuous oscillations with main frequency in theta band (7.03 ± 0.15 Hz, n = 398 events from 15 pups) were additionally present (Table S3; Figure S3B). They represent the dominant pattern of slow oscillatory activity in the neonatal Hipp. Since their mechanisms of generation are still unknown and might differ from those of the adult theta rhythms, we defined these events as hippocampal theta bursts. About one-third of the theta bursts (136 out of 398 events) were accompanied by SPWs. Their duration and maximal amplitude were significantly (p < 0.001) higher than of the theta bursts without superimposed SPWs (Table S3). As previously reported (Palva et al., 2000 and Lahtinen et al., 2002), gamma oscillations and ripples developed toward the end of the first postnatal week and appeared superimposed on theta bursts and SPWs, respectively.