Fig. 7. Positioning the shunting electrodes farther away from the side of the fish reduces the current shunted during an electric organ discharge (EOD) but leaves the distribution of responsiveness across phases constant. (A) Recording of EOD current shunted during prolonged switch closure when the shunt electrodes were placed at three lateral displacements, successively farther away from the fish cage (0, 1 or 2 cm). Each point of the waveforms predicts the magnitude of EOD current that is shunted when the electronic switch is closed during an interval that centers at this point. An example of the head—tail EODs, recorded simultaneously, is shown below as a phase reference. (B) Response probabilities obtained as the switch was closed for 100 µs either during one of the extrema V₂, V₃ or V₄, or 4 ms after onset of the EOD (Control). For each of the three distances, 100 responses were recorded at each of the four stimulus conditions (total of 1200 tests on fish 6). The baseline response probability (due to spontaneous rate fluctuations) is given by the dotted horizontal line (pooled from 100 recordings without switch closure at each distance). There was no significant difference between baseline and controls. At all distances, responsiveness in V₄ is significantly higher than in V₃ (P<0.001) and higher in V₃ than in V₂ (P<0.05). All response levels are significantly above baseline except for those at distances 1 and 2 cm in phase V₂. Decrease in responsiveness with distance is significant in V₄ (0-1 cm: P<0.01) and V₃ (0-2 cm: P<0.05).

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