Biosonar Performance and Processing in FM Bats

摘要

Identification of the excitatory FM-sweep frequency for a representative IC neuron by reverse correlation (REVCOR) analysis, a method that searches over the time-interval prior to each spike to find any common element in all the stimuli that precedes responses. Graphs show the frequency which drives responses to simulated sonar pulses (A) or echoes (B) for fixed FM sweep-widths with different durations and thus different sweep rates. In each plot, the shaded FM sweeps with different slopes appear to rotate about a common point in time-frequency space at about 27-28 kHz and a fixed time of about 15-16 ms prior to the neuron's spikes. This is a unique point because the response is just one spike per sound. The point identifies the location along the sweep that delivers excitation to the cell and registers the cell's characteristic latency (its 'delay-tap' value). This point also specifies the time and frequency dimensions of a new time-frequency representation that the IC substitutes for the original spectrogram created by the inner ear.