Simultaneous Extracellular and Intracellular Recordings of Spontaneous Rhythmic Activities. Upper panel shows the extracellular local field potential – Spontaneous Rhythmic Field Potentials (SRFPs) are clearly visible. The illustrated extracellular recording is from the CA3 apical dendritic region so that SRFP deflections are negative (downward). The bottom panel shows the simultaneous intracellular recording from a CA3 pyramidal neuron. The circled regions are examples of SRFP episodes. The injected current value for the intracellular trace is 0.16 nA.