We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
What Do Evoked Potentials Tell Us About the Acoustic System of the Harbor Porpoise?
- Authors
Bibikov, N. G.
- Abstract
The evoked acoustic potentials of the brainstem (EAPB) were detected from the brain, the skull, and the surface of the head of the harbor porpoise (Phocaena phocaena). Experiments were performed at the Karadag biological station (Crimea). Clicks, noise, and tone bursts of different frequencies within 80–190 kHz were used as stimuli. The time and frequency selectivities of the auditory system were estimated by the simultaneous and direct forward masking methods. The minima of EAPB thresholds were usually observed in a frequency range of 120–140 kHz, which corresponded to the main spectral maximum of the species-specific echolocation signal. In addition to the regular EAPB, a pronounced off-EAPB was observed. In the aforementioned frequency range, a frequency selectivity (Q10 of about 10) was revealed by the direct forward masking method. The EAPB could be measured up to a frequency of 190 kHz, but outside this high-resolution region (outside the ultrasonic ‘fovea’), the frequency selectivity was weak. A simultaneous masking of a click by a tone was strong only when the delay of the click with respect to the masker onset was smaller than 1.0 ms. In a continuous regime, the tone (unlike noise) produced only a weak masking. The response to a small intensity increment of 1–4 dB was rather strong. In the frequency range of 120–140 kHz, this response exhibited a nonmonotone dependence on the signal level. The time resolving power, which was measured by the EAPB recovery functions for double clicks of various levels, was rather high, even when the intensity of the test signal was 18 dB lower than the masker level. Experimental data show that the auditory system of the harbor porpoise is tuned to detecting ultrasonic echo signals in the frequency range within 120–140 kHz. A hypothesis is put forward that the acoustic system of the harbor porpoise allows the animal, from analyzing echo signals, to estimate not only the distance to the target and the target's intrinsic properties but also the speed with which the target is approached, the latter estimate being presumably obtained on the basis of the Doppler effect.
- Subjects
BRAIN stem; HARBOR porpoise; SOUND waves; VOICE frequency; DOPPLER effect; BIOACOUSTICS
- Publication
Acoustical Physics, 2004, Vol 50, Issue 3, p295
- ISSN
1063-7710
- Publication type
Article
- DOI
10.1134/1.1739498