The amplitude-latency trade-off demonstrates a temporal basis for fine echo delay acuity in bat sonar

Abstract

Echolocating bats (Eptesicus fuscus) can perceive a change in echo delay smaller than 1 μs in two-choice, echo-jitter discrimination tasks. Although the bats emit sounds short enough to avoid overlap of stimulus echoes with incidental echoes, and although the transfer function of the delay electronics reveals no amplitude or spectral cues correlated with delay, it is difficult to believe that such fine temporal is not based on spectral cues. If the delay of echoes is encoded by neural discharge timing rather than from spectral information, perceived delay should shift according to the neural amplitude-latency trading function, which is − 13 to − 18 μs/dB for N1-N4 responses in Eptesicus. The apparent delay of echoes in the jitter task shifts by − 16 to − 17 μs/dB, demonstrating that the bats perceive the delay of jittered echoes from their arrival time rather than from some spectral consequence of the particular value of echo delay. The corresponding shift of the entire jitter psychometric function demonstrates that bats may perceive the phase of echoes relative to emissions from information encoded in the timing of neural discharges, as previously proposed from coincidence of the jitter psychometric function with the cross-correlation function of echoes.