Fig 2. Electrode position and the hippocampal local field potential (LFP).

(A) Typical electrode position in the dorsal hippocampus. The arrows indicate the tips of the twisted electrode, which were marked electrically after the completion of behavioral experiment. (B) Typical hippocampal LFP data around the lever press. The LFP data in four trials are shown on a longer and shorter time scale in upper and lower traces, respectively. The times before the first lever press are indicated as negative values. Horizontal lines under each LFP trace indicate the lever presses. The rat took a food from the robot after the final lever off, indicated by arrowheads in the upper traces. (C) Typical power spectral density of the hippocampal LFP during a session, plotted in arbitrary units.