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First published online December 14, 2007
Journal of Experimental Biology 211, 9-14 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.012823

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Time-variant spectral peak and notch detection in echolocation-call sequences in bats

Daria Genzel^* and Lutz Wiegrebe

Department of Biologie II, Universität München, Großhadernerstr. 2 82152 Planegg-Martinsried, Germany

View larger version (21K): [in this window] [in a new window]   Fig. 1. Spectrograms of the echolocation-call sequences with the time-variant peaks (A,B) and notches (C,D). To the left of A and C is the spectrogram of the unfiltered FM sweep consisting of F0 (23 to 19 kHz) and four harmonics with a duration of 1.5 ms. A and B show the echolocation-call sequences to be discriminated for the time-variant peak detection. C and D show the echolocation-call sequences to be discriminated for the time-variant notch detection. All echolocation-call sequences have a modulation depth of 40% of the centre frequency (CF) and a modulation rate of 16 Hz, which results in an overall duration of 125 ms.

View larger version (23K): [in this window] [in a new window]   Fig. 2. (A–D) Mean psychometric functions for all bats for the time-variant peak detection for the tested modulation rates (MR) of 2, 4, 8 and 16 Hz, respectively. Plotted are percent correct decisions as a function of the modulation depths; the significant threshold level was set to 75%. Each panel depicts the psychometrics curves for all animals as a function of modulation depth. The threshold is calculated as a mean value for all bats.

View larger version (8K): [in this window] [in a new window]   Fig. 3. Psychometric functions for the time-variant peak detection for one bat for the modulation rate (MR) of 4 Hz. The solid line represents the performance with an initial training at a modulation depth of 40% of centre frequency (CF). The dotted line displays the same bat's performance for the same experimental condition, only with an initial training at a modulation depth of 100% of CF.

View larger version (22K): [in this window] [in a new window]   Fig. 4. (A–D) Mean psychometric functions for all bats for the time-variant notch detection for the tested modulation rates (MR). Data are shown in the same format as in Fig. 2.