It also merits emphasis that the relationship between synaptic activity and the LFP is complex due to several factors. One is the membrane capacitance that slows down the dynamics of membrane potential (Cole, 1968) and creates a nonlinearity between membrane potential and transmembrane current (Martin, 1976). Dynamic changes in ionic conductance states also contribute to the nonlinearity (Borg-Graham et al., 1998). In contrast, transmembrane currents create extracellular current sinks/sources, and these are directly related to the extracellular potential by Poisson's equation, as incorporated into the CSD method (Freeman and Stone, 1969;Mitzdorf, 1985). In typical (densely packed) cases, the relative strength and symmetry of activation in two adjacent generator substrates determines which is better represented over the surrounding volume of tissue [e.g., (Givre et al., 1995;Tenke et al., 1993)].
