Fig. 1. (A) Schema of experimental paradigm, showing the object (a metal plate), the receptive field on the skin surface (gray circle) and the position of the electrode pair used to record the local electric organ discharge (LEOD). (B) Photomicrograph of the electrosensory lobe (ELL) in cross section, showing the position of the microelectrode recording field potentials in the granular layer. (C) Comparison of LEODs recorded at the receptive surface and field potentials recorded in the ELL for the control situation without any external object and in the presence of a variety of objects of different conductivity but similar in volume and form, aligned with the center of the receptive field. Left column: LEOD recorded at the receptive field center (green). Middle column: field potentials recorded in the ELL in the presence of a reafferent sensory input (red) and in the absence of reafferent sensory input (black). To obtain the latter traces, the output of the electric organ was shunted with a metal plate close to the tail: in this case reafferent sensory input is absent and the field potential corresponds to the effect of the corollary discharge alone. Right column: the field potential equivalent to the sensory response (FPSR; blue) calculated as the difference between the recordings with and without reafferent input (red minus black traces in middle column). Field potentials are averages of 10 traces.