Different network states and corresponding unit activity can be analyzed in the in vitro model.

A: Schematics of recording conditions. Tetrode recordings are performed in the pyramidal cell layers of CA3 and CA1. During sharp wave-ripple oscillations (SPW-R), field potentials are generated by the recurrent network of CA3 (green) and transmitted via the Schaffer collaterals to selectively activate cell assemblies in CA1 (red). Examples of field potential waveforms are shown in the respective colors. B: Example traces of field potentials recorded in CA1 during SPW-R (left panel) and gamma oscillations (right panel). Raw field potential (upper trace) and the high pass filtered (0.5–10 kHz) potential in the four tetrode channels (lower traces). Filtering reveals high-frequency multiunit activity on SPW-R and gamma cycles. Firing of two individual units extracted by waveform analysis is highlighted in orange and blue. Time points of firing relative to the field potential are visualized by vertical ‘ticks’. The middle panel illustrates the detection criterion for unit events: horizontal histograms of all data points show largely normal distribution around zero. Events are detected if they exceed 4.5 times the standard deviation as indicated by the dashed red line. C: Wavelet spectrograms of the example traces from B. Sharp waves are superimposed by high-frequency ripple oscillations (∼200 Hz, left panel). The carbachol-induced gamma state consists of a continuous oscillation at ∼30 Hz.