A. Denzinger et Hu. Schnitzler, ECHO SPL, TRAINING EXPERIENCE, AND EXPERIMENTAL PROCEDURE INFLUENCE THE RANGING PERFORMANCE IN THE BIG BROWN BAT, EPTESICUS-FUSCUS, Journal of comparative physiology. A, Sensory, neural, and behavioral physiology, 183(2), 1998, pp. 213-224
Four Eptesicus fuscus were trained in a range discrimination experimen
t to choose the closer of two phantom targets. Echo attenuation was ro
ving between trials returning echoes ranging from -10 dB to -50 dB SPL
(sound pressure level) relative to emission SPL. Discrimination thres
holds were determined. After sufficient training, ranging performance
was stable and about the same in the range between -20 dB and -50 dB w
ith range difference thresholds around 300 mu s. At -10 dB, performanc
e was poor even after long training. After additional training at a co
nstant relative echo SPL of -30 dB and a delay difference of 300 mu s
the performance measured with roving echo SPL improved at all relative
echo SPL between -20 dB and -50 dB but not at -10 dB. The new experim
ental procedure improved the performance by additional learning, and t
he bats generalized over a wide range of relative echo SPL. Threshold
improved to 100 mu s when measured at a constant relative echo SPL of
-30 dB, again indicating the influence of the experimental procedure.
In correspondence to neurophysiological data the ranging performance d
eteriorates if the echo SPL is close to the emission SPL. Signal durat
ion and emission SPL were variable during range discrimination.