(A) Representative mean evoked potentials (n = 10 traces) from the EL of P. tenuicauda (black), ELa of P. microphthalmus (blue), and ELa of B. niger (red) in response to single-cycle bipolar sinusoidal pulses with durations of 0.5ms (left) and 0.1 ms (right), which correspond to peak power frequencies of 1.7 and 8.4 kHz, respectively. Frequency tuning curves of the midbrain exterolateral nucleus (EL) in P. tenuicauda (B), and the anterior (ELa) and posterior (ELp) subnuclei of EL in P. microphthalmus (C and D, respectively) and B. niger (E and F, respectively). Evoked potentials in P. tenuicauda were obtained throughout EL, in locations varying from more anterior to more posterior, as in (i) and (ii) in Figure 1A. Frequency tuning curves were obtained at three intensities: 73.6 (full lines), 23.4 (dashed lines), and 7.4 (dotted lines) mV/cm. We measured the peak-to-peak amplitude of the evoked potential at each frequency and intensity, and normalized them to the maximum value for each fish and each nucleus separately. Gray boxes represent the frequencies between the peak power frequency (ppf) of the conspecific EOD and one octave below the ppf. Each symbol in (B), (C), (D), (E), and (F) represent the mean normalized amplitude and the error bars represent the S.E.M.