Susanne Hoffmann, Leonie Baier, Frank Borina, Gerd Schuller, Lutz Wiegrebe and Uwe Firzlaff (2008): Psychophysical and neurophysiological hearing thresholds in the bat Phyllostomus discolor. J. Comp. Physiol. A 194(1), 39-47
Abstract: Absolute hearing thresholds in the spear-nosed bat Phyllostomus discolor have been determined both with psychophysical and neurophysiological methods. Neurophysiological data have been obtained from two different structures of the ascending auditory pathway, the inferior colliculus and the auditory cortex. Minimum auditory thresholds of neurons are very similar in both structures. Lowest absolute thresholds of 0 dB SPL are reached at frequencies from about 35 to 55 kHz in both cases. Overall behavioural sensitivity is roughly 20 dB better than neural sensitivity. The behavioural audiogram shows a first threshold dip around 23 kHz but threshold was lowest at 80 kHz (−10 dB SPL). This high sensitivity at 80 kHz is not reflected in the neural data. The data suggest that P. discolor has considerably better absolute auditory thresholds than estimated previously. The psychophysical and neurophysiological data are compared to other phyllostomid bats and differences are discussed. URL: http://www.springerlink.com/content/05660v5416m72225/ For reprints please contact Susanne Hoffmann (Email: [EMAIL PROTECTED]) Sven Schörnich and Lutz Wiegrebe (2008): Phase sensitivity in bat sonar revisited. J. Comp. Physiol. A 194(1), 61-67. Abstract: An echolocating bat produces echoes consisting of the convolution of echolocation call and the impulse response (IR) of the ensonified object. A crucial question in animal sonar is whether bats are able to extract this IR from the echo. The bat inner ear generates a frequency representation of call and echo and IR extraction in the frequency domain requires accurate analysis of both magnitude and phase information. Previous studies investigating the phase sensitivity of bats using a jitter paradigm reported a temporal acuity down to 10 ns, suggesting perfect sonar phase representation. In a phantom-target playback experiment, we investigate the perceptual phase sensitivity of the bat Phyllostomus discolor using a novel approach: instead of manipulating IR phase by changing IR delay (jitter paradigm), we randomized IR phase and thus lengthened the IR over time, leaving the magnitude spectrum unchanged. Our results show that phase sensitivity, as reflected in the analysis of signal duration, appears to be much lower than phase sensitivity, as reflected in the analysis of signal onset. The current data indicate that different temporal aspects of sonar processing are encoded with very different temporal resolution and thus an overall claim of “phase sensitivity” as such cannot be maintained. URL: http://www.springerlink.com/content/6070mr5463545131/ For reprints please contact Sven Schörnich (Email: [EMAIL PROTECTED]) Roger D. Santer, Yoshifumi Yamawaki, F. Claire Rind and Peter J. Simmons (2008): Phonotactic response of female crickets on the Kramer treadmill: methodology, sensory and behavioural implications. J. Comp. Physiol. A 194(1), 79-96. Abstract: Since population-level variation in female mating preferences can shape intraspecific communication systems within the context of sexual selection it is essential to quantify these preferences and their sources of variation. We calculated individual female response functions for four male calling song traits in the field cricket Gryllus bimaculatus, by performing untethered phonotaxis measurements on a spherical locomotor compensator (Kramer treadmill). Firstly, we quantify the population-level sources of phonotactic variation and correct for factors that adversely affect this measurement. Secondly, we develop methodology for the characterisation of individual female phonotactic response functions suitable for population-level analyses and demonstrate the applicability of our method with respect to recent literature on Orthopteran acoustic communication. Phonotaxis towards a preferred stimulus on different occasions is highly repeatable, with lower repeatabilities away from the most preferred signal traits. For certain male signal traits, female preference and selectivity are highly repeatable. Although phonotactic response magnitude deteriorated with age, preference functions of females remained the same during their lifetimes. Finally, the limitations of measuring phonotaxis using a spherical locomotor compensator are described and discussed with respect to the estimation of the selectivity of female response. URL: http://www.springerlink.com/content/a4u81m0731771272/ For reprints please contact L. Verburgt (Email: [EMAIL PROTECTED]) Kind regards Sonja Amoser
