, 2001) and has characteristically distinct gene profiles (Thomps

, 2001) and has characteristically distinct gene profiles (Thompson et al., 2008; Dong et al., 2009). In return, the septal and temporal segments of the hippocampus broadcast to different streams of structures (Amaral and Lavenex, 2007; Cenquizca and Swanson, 2007). In contrast to its afferent and efferent connections, the internal organization of the hippocampus suggests that the widespread neocortical representations are integrated (cf., Bannerman et al., 2003; Bast et al., 2009; Kjelstrup et al., 2002; Moser et al., 2008; Small, 2002; Royer et al., 2010) by the

extensive recurrent collateral system of CA3 pyramidal neurons (Ishizuka et al., 1990; Li et al., 1994). The physiological mechanisms of communication between click here the hippocampus and the

neocortex are not well understood. Neuronal recording studies from the septal and more temporal segments of the hippocampus are controversial and range from emphasizing the unity of hippocampal Vorinostat supplier operations (O’Keefe and Nadel, 1978; Bullock et al., 1990; Jung et al., 1994; Kjelstrup et al., 2008; Lubenov and Siapas, 2009; Maurer et al., 2005) to more localized and specialized computations (Hampson et al., 1999; Royer et al., 2010; Segal et al., 2010; Wiener, 1996). A fundamental mode of hippocampal operations is reflected by theta oscillations during explorative behavior and REM sleep (4–10 Hz; cf., Buzsáki, 2002). In a recent elegant study Lubenov and Siapas (2009) have observed that the phase of theta waves advances systematically in the dorsal hippocampus (Lubenov and Siapas, 2009) and hypothesized a full cycle (i.e., 360°) phase shift between the septal and temporal poles. The implication of a full-cycle phase shift of theta waves is that outputs from not the two poles of the hippocampus would affect their joint targets in a temporally synchronous manner, while the intermediate parts would remain temporally segregated from either pole.

To examine the spatial organization of theta patterns, we recorded LFP and neuronal discharge activity in the subiculofimbrial (transverse) axis and from the entire length of the septotemporal (longitudinal) axis of the hippocampal CA1 pyramidal layer during behavioral exploration and REM sleep. LFP and unit activity were recorded during REM sleep in the home cage and during navigation (RUN sessions) either while the rat was chasing small fragments of randomly dispersed froot loops on an open field and/or running for a water reward in an 11-compartment zig-zag maze (Royer et al., 2010). Since the phase of theta oscillation in the CA1 region varies along the somatodendritic (depth), subicular-CA3 (transverse), and septotemporal (dorsoventral or longitudinal) axes (Buzsáki, 2002; Lubenov and Siapas, 2009; Patel et al., 2008, Soc. Neurosci., abstract, 435.

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