Fig. 4.

Dependence of JAR and LTFE magnitude on stimulus parameters. a, Mean changes in EOD frequency during JAR and after stimulus period (LTFE) in different groups of fish and in response to different stimulus durations at 1 mV/cm stimulus amplitude. The values were determined by measuring the elevation from baseline to stable frequency during JAR and after stimulus offset (Fig. 2). The JAR for the 2-min-long presentation was not included, because the JAR magnitude here is more similar to the initial first minutes of the JAR during the long presentations, which is usually higher than the stable frequency during these presentations and does not reflect overall magnitude of the JAR (Fig. 2b). The mean JAR for the long presentations (30 and 180 min) is not affected by the stimulus duration (30 min, n = 10; 180 min,n = 9; p > 0.5). Mean LTFE is significantly higher for the long presentations than for the 2-min-long presentation (2 min, n = 21; all comparisons,p < 0.05), but the increase in mean LTFE between 30 and 180 min stimulated groups is not significant (p > 0.3). b, Mean JAR and LTFE for different stimulus amplitudes in different groups of fish at 3 hr stimulus length for the long presentation. The JAR becomes significantly larger with increasing stimulus amplitude (1 mV/cm,n = 9; 15 mV/cm, n = 9; 100 mV/cm, n = 5; p < 0.05, all groups significantly different from each other). In correspondence, mean LTFE increases (1 mV/cm, n = 9; 15 mV/cm,n = 9; 100 mV/cm, n = 6;p < 0.05, 1 mV/cm group not significantly different from 15 mV/cm group). Note that, for 100 mV/cm, mean LTFE is almost as high as the JAR (Fig. 2b). a,b, The resting EOD frequency before onset of all stimulus experiments was fairly stable, with an average baseline frequency change of −0.36 ± 0.15 Hz, measured for 3 hr before stimulus onset (n = 31). The 180 min group ina is the same than 1 mV/cm group inb.