Detection of frequency modulation in the FM-bat Phyllostomus discolor.
In a two-alternative forced-choice procedure lesser spear-nosed bats, Phyllostomus discolor, had to discriminate between a pure tone stimulus and a sinusoidally frequency-modulated signal generated at the same carrier frequency as the tone. Modulation depths of the SFM stimuli were reduced until the animals' performance dropped below the 75%-correct level which was used to determine difference limens for detection of frequency modulation (FMDL). The dependence of FMDLs on modulation and carrier frequency was systematically investigated. For a carrier frequency of 18.5 kHz, average FMDLs increased from 95 Hz at a modulation frequency of 10 Hz to 820 Hz at a modulation frequency of 2000 Hz which corresponds to Weber ratios (2 delta f/f) of 0.005 and 0.044 respectively. Further, difference limens were found to increase linearly in proportion to carrier frequency throughout a major part (9-74 kHz) of the species' hearing range. In comparison to other mammals, P. discolor has a pronounced capability for frequency discrimination which might be related to the extensive use of individually distinct frequency-modulated communication calls and audio-vocal learning.
Esser
K H
KH
Abteilung Vergleichende Neurobiologie, Universität Ulm, Germany.
Kiefer
R
R
D000161:Acoustic Stimulation; D000818:Animals; D001301:Audiometry, Pure-Tone; D002138:Calibration; D002685:Chiroptera / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology; D003216:Conditioning, Operant / Q000502:physiology; D004455:Echolocation / Q000502:physiology; D005583:Fourier Analysis; D008144:Loudness Perception / Q000502:physiology; D008297:Male; D010898:Pitch Perception / Q000502:physiology*