Fig. 8. Experiments in which electric organ discharge (EOD) current was shunted for 100 µs at various phases of the EOD. The horizontal width and position of the bars indicate the timing of switch closure relative to the head—tail EOD (red trace). The height of each bar indicates the experimentally determined response probability when the switch was closed during the indicated period of the EOD. The dotted horizontal line gives the baseline responsiveness (due to spontaneous fluctuations in discharge rate) determined from 100 recordings without switch closure. Responsiveness in the controls was not above baseline, but switch closure within the EOD led to sigificantly higher than baseline responsiveness (at least P<0.01). Responsiveness in V₄ was significantly higher (P<0.001) than in V₃ but differed not significantly from that determined in the phase after V₄. A total of 1070 tests (100 in each condition, except for phase V₄ and for controls after the EOD, in which 200 and 270 tests, respectively, were conducted). Data from fish 6. Electrode positions as indicated in Fig. 5.