Fig. 3. The responsiveness of the fast electrosensory pathway decreases with the intensity of the conditioning stimuli. To assess the effect of activation of the fast electrosensory pathway on its responsiveness, the amplitude of the response of the magnocellularis nucleus to an artificial test stimulus of intensity 2x the threshold was studied as a function of the amplitude of an artificial conditioning stimulus, and the delay between conditioning and test stimuli, in a curarized fish. The amplitude of the test response (as a percentage of its maximal response) is plotted as a function of the delay between conditioning and test stimuli for eight conditioning stimulus intensities (0–10x threshold).