Three's a crowd? PredictingEigenmannia's responses to multiple jamming

Abstract

We have studied Jamming Avoidance Responses (JARs) ofEigenmannia in the presence of more than one interfering signal. Experiments were performed on intact as well as curarized specimens, whose silenced electric organ discharge (EOD) was replaced by a sine wave,S1 of frequency,F1. Sine waves,S2 andS3, with respective frequencies,F2 andF3, mimicked EODs of two potential neighbors. Much as in the case of a single interfering signal,S2 (Heiligenberg and Bastian, 1980), the presentation of two interfering signals,S2 andS3, results in modulations of phase,H(t), and amplitude, ¦S¦(t), of the animal's contaminated EOD or its substitute,S1, and these modulations drive the JAR. The plots ofH and ¦S¦, as variables in a two-dimensional state-plane, yield graphs in the manner of Lissajous Figures whose shape depends upon the relative intensities, ¦S2¦/¦S1¦ and ¦S3¦/¦S1¦, and the differences in frequencies,ΔF2=F2−F1 andΔF3=F3-F1, of the two stimuli,S2 andS3 (Figs. 1 to 5). On the basis of such graphs, JARs to multiple stimuli can be predicted (Figs. 5 to 7) by a line integration algorithm (Fig. 9) originally developed for the single stimulus case (Heiligenberg and Bastian, 1980). This model, which should predict JARs to any number of interfering stimuli, assumes that the effect of an entire graph is the integral of incremental contributions by line segments which constitute this graph, with the effect of a single line segment depending upon its location and orientation within the state-plane. As a consequence of this mechanism, the animal most strongly avoids the frequency vicinity of the strongest and thus most detrimental stimulus without the necessity of identifying intensities and frequencies of any stimuli in the jamming regime.