Representation of sinusoid ‘‘ramps’’ and ‘‘damps’’ in auditory‐nerve fibers of the goldfish

Earlier, behavioral data was presented showing that goldfish perceive repeated, asymmetrically shaped 400‐Hz tone bursts (ramps and damps) qualitatively as humans do: Ramps are more tonelike than damps [R. Fay and R. Patterson, 2941 (A) (1994)]. Ramps have slow rise and relatively fast fall envelopes. Damps are ramps played backward. Single auditory‐nerve fibers were recorded in response to the same ramp and damp stimuli used in the behavioral studies. Spike times were recorded for two presentations of six, 3‐s stimuli: Ramps with 25‐, 35‐, and 45‐ms rise times and 5‐ms fall times, and these stimuli played backward (damps), presented at several levels. Tuning was described using REVCOR analysis and by spike count functions of frequency at several levels. Responsiveness was defined using the coefficient of synchronization (R) over the carrier period, the number of spikes evoked (N), and the statistic Z where Z=R2N. For most fibers, R, N, and Z were greater for ramps than for the corresponding damps. This n...