Figure 1 A. Snapshots in time (every 10 ms) of a spatially filtered optical recording for a hippocampal-entorhinal slice during theta oscillation. The amplitude of the signal is color-coded: increases in relative fluorescence in yellow and red (depolarization), reduction in relative fluorescence in green and blue (hyperpolarization). One cycle of the oscillation is shown; see B for the indication of the interval and the timing of each snapshot (time of snapshots indicated by the vertical lines). The maximum of the oscillatory wave (a depolarization) is first detected in the EC and subsequently in the Sub and the DG. After the DG it is then observed the CA3 and CA1 region. B. Amplitude tracings of four optical channels, situated in the entorhinal cortex (red), subiculum (blue), CA3 (black) and CA1 (magenta) during theta oscillation (the location of these channels is indicated in C). Zero time is the maximum amplitude in EC. C. Picture of the hippocampal-entorhinal cortex slice. The red hexagonal is the outline of the photodiode array; the outline of the hippocampus and the entorhinal cortex is represented in black. The blue, red, magenta and black dots represent the optical channels represented in the tracings B. (Cappaert et al., Hippocampus, 2009)

Figure 2. Retrosplenial and hippocampal–parahippocampal connectome of the rat. The connectome consists of 14 large, color-coded boxes, which represent the sub-regions of the hippocampal formation, parahippocampal region, and retrosplenial cortex (van Strien et al., Nature Reveiws Neuroscience, 2009; Sugar et al., Frontiers in Neuroinformatics, 2011). Go to www.temproral-lobe.com to download the interactive pdf of the connectome.