Fig. 1.

Neural code organized by theta and gamma oscillations. (A) Simultaneous extracellular (top) and intracellular (bottom) recordings from the hippocampus. Intracellular gamma is due to IPSPs, the amplitude of which is modulated by the phase of theta. From Fig. 4C of (Penttonen et al., 1998). (B) Schematic of the theta-gamma code. The ovals at top represent states of the same network during two gamma cycles (active cells are black and constitute the ensemble that codes for a particular item). Different ensembles are active in different gamma cycles.