Fig. 2. Electrosensory coding by field potentials and primary afferent unit activity. (A) Change in area of the negative peak of the field potential equivalent to the sensory response (FPSR) plotted as a function of the peak-to-peak amplitude of the local electric organ discharge (LEOD), when a metal plate (black circles) or plastic plate (red diamonds) were placed parallel to the fish in the region of the electric organ, at increasing distances lateral to the fish's body. Zero represents the control value, in the absence of any object. (B) Area of the negative peak of the FPSR as a function of its latency at half-amplitude. (C) Raster plot of the activity of a single afferent fiber while a metal object was moved along the side of the fish. The vertical lines indicate the mean latencies of spike timing in the absence of any object (two spikes only). (D) Interval between the first and the second spikes as a function of the latency of the first spike after the motor command. Points of different colors correspond to data from different primary afferent units recorded in the same fish.