Correlated amplitude fluctuations of spontaneous otoacoustic emissions in six lizard species

Abstract

Spontaneous otoacoustic emissions were recorded from 17 lizard ears (six species: Gerrhosaurus major, Iguana iguana, Basiliscus vittatus, Tupinambis teguixin, Varanus exanthematicus, and Cordylus tropidosternum). The spectrum of each recording contained multiple spectral peaks. For each peak, the envelope cross-correlation R(τ) with all other peaks from the same ear was computed. Of the total of 346 emission peak pairs, 58 (17%) showed a significant correlation. Thus like in humans, multiple emission peaks in lizards frequently interact. In the lizards, the cross-correlation was positive in 30 cases, and negative in 28 cases. The cross-correlation function peaked at either a positive (τpeak>0) or a negative (τpeak<0) delay time. Peak delays ranged from −3.7 ms to 6.2 ms with an average 0.2 ms (s.d. 1.8 ms). The range of observed peak delay values differs from that in human [average τpeak=11.0 ms (s.d. 22.1 ms)].