QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online December 14, 2007
Journal of Experimental Biology 211, 106-113 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.009688

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bates, M. E. Articles by Simmons, J. A. Search for Related Content PubMed PubMed Citation Articles by Bates, M. E. Articles by Simmons, J. A.

Jamming avoidance response of big brown bats in target detection

Mary E. Bates^1,*, Sarah A. Stamper² and James A. Simmons²

¹ Department of Psychology, Brown University, Providence, RI 02912, USA
² Department of Neuroscience, Brown University, Providence, RI 02912, USA

View larger version (24K): [in this window] [in a new window]   Fig. 1. Spectrograms of sonar sounds emitted by a big brown bat in target-detection tasks while wideband random noise of different amplitudes was delivered from a loudspeaker (Simmons et al., 1974). In response to the noise, the bat lengthens its FM sweeps, which have a curvilinear shape and tail down to a shallow sweep around 22–28 kHz (arrow). Its detection performance remains approximately constant in ambient conditions and in –40 to –10 dB noise, but it declines to chance in 0 dB noise.

View larger version (12K): [in this window] [in a new window]   Fig. 2. Diagram of experimental set-up. Bats were trained to sit on the Y-shaped platform and search for the target located 30 cm away, responding by moving forward onto the corresponding platform arm for food reward. CF jamming sounds were presented from the loudspeaker located 1.5 m away, and the bat's sonar sounds were recorded by microphones located 1.5 m away and separated by 30°.

View larger version (14K): [in this window] [in a new window]   Fig. 3. Frequencies and sound pressures of constant-frequency (CF) jamming sounds in relation to the audiogram of big brown bats. (A) Full frequency range. (B) Expanded frequency range used for jamming experiments. At frequencies of 18–32 kHz, the jamming stimuli have a constant sensation level of about 65 dB. Filled symbols indicate CF jamming stimuli; other symbols indicate individual animals. [Replotted from Dalland (Dalland, 1965) and Koay et al. (Koay et al., 1997).]

View larger version (7K): [in this window] [in a new window]   Fig. 4. Plot showing percentage of correct trials averaged across the three bats (F11,22=1.691, P=0.142). N=30 trials per data point (10 per bat).

View larger version (5K): [in this window] [in a new window]   Fig. 5. Individual bats' mean baseline terminal frequencies for first-harmonic FM sweeps with 99% confidence intervals (Marina, N=130; Snuffles, N=249; Vlad, N=457).

View larger version (6K): [in this window] [in a new window]   Fig. 6 Mean tail-end frequency averaged across bats for CF jamming off trials and initial pre-testing baseline. Bars indicate 99% confidence intervals.

View larger version (35K): [in this window] [in a new window]   Fig. 7. Plots showing jamming avoidance response (terminal first-harmonic frequencies). (A) Size of frequency change in raw frequency coordinates with 99% confidence intervals. Black points, CF jamming stimulus on; white points, CF jamming stimulus off. Arrows (fbase) indicate the mean pre-testing baseline frequency of each bat (see Fig. 5). (B) Plots showing change in frequency relative to CF off frequencies.

View larger version (6K): [in this window] [in a new window]   Fig. 8. Plot of durations of broadcasts during trials at each CF jamming frequency with 99% confidence intervals. Only the duration of the sounds emitted during the trials in which the CF jamming stimulus was present (10 trials per bat per frequency) are plotted.

View larger version (18K): [in this window] [in a new window]   Fig. 9. A typical big brown bat echolocation sound (left) with sharpness of frequency tuning for neurons in the bat's cochlear nucleus (CN) and inferior colliculus (IC) [replotted from Haplea et al. (Haplea et al., 1994)]. The horizontal broken line indicates where the sweep tails off in the first harmonic at approximately 23 kHz. With no other constraints, frequencies within this range are used for target detection. In this example, IC tuning is much sharper at frequencies around 23–25 kHz, with Q10dB values ranging from 2 to 40, and some as high as 90.