The fluctuation of neuronal membrane potential around the mean without generating APs is known as SMO. This oscillation has a power spectrum with peaks at regionally specific resonant frequency bands, for instance olivary neurons ∼5 Hz (Devor and Yarom, 2002a), entorhinal cortical neurons 4–7 Hz (Giocomo et al., 2007), and cortical neurons ∼40 Hz (Llinas et al., 1991; Silva et al., 1991). The most likely sources of such oscillations are specific intrinsic conductances (White et al., 1998; Dickson et al., 2000; Fransen et al., 2004). However, the coherency of SMOs across neurons depends on electrotonic interactions between neurons (Devor and Yarom, 2002b). A number of mechanisms, including gap junctions, electrotonic synapses, ephaptic conductivity, and glial transfer (Yeh et al., 1996), have been proposed to mediate SMOs between neurons. These mechanisms allow the SMO to propagate in a radial spread or traveling waves, depending on the network architecture. Moreover, near-synchronized activity of interneurons impinging on different parts of principal cells may also sculpt such oscillations (Buzsaki and Chrobak, 1995).