Volume 30 #3

Contents

1. The structural-functional organization of mammalian auditory cortex as the basis of acoustic information cortical processing. The structural organization
2. Allocation of the characteristic features of in low-frequency envelope of the tone by the neurons in the midbrain auditory center of the frog
3. Discrimination of sound signals with rippled spectra in the noises of different spectral compositions
4. Temporary threshold shifts in naïve and experienced belugas
5. The role of simpatic-epinephrine system in the changes of electrical activity of the brain hemisphere cortex and hypothalamus under vibration exposure
6. Cyclic polypeptide PP-14 modulates the voltage sensitivity of slow sodium channels
7. Training optimal Viola–Jones detectors using greedy algorithms for selecting control parameters with intermediate validation on each level
8. Abnormal band in the circular dichroism spectrum of DNA cholesteric liquid-crystalline dispersions – an analytical criteriom for detection of coloured biologically active compounds

Effects of fatiguing nose were investigated in five belugas Delphinapterus leucas. In each of the subjects, substantial difference was noticed between effects in the first and second and later experimental sessions. In the first session (naïve subject state), temporary threshold shift (TTS) produced by exposure to fatiguing noise was substantially larger than TTS produced by the very same noise in subsequent sessions (experienced subject state). After two to three sessions, TTS stabilized. The difference between TTS in the naïve and experienced states was 10 to 15 dB. The baseline hearing thresholds (no exposure to fatiguing sound or before exposure) did not differ in the naïve and experienced states. A possible explanation of this effect is that gaining experience, the animal learned to dampen its hearing during the action of the fatiguing noise, thus mitigating its impact. This effect should be taken into consideration when experimental data obtained in captive experienced odontocetes are used to predict effects of noise on wild inexperienced animals.

Key words: hearing, toothed whales, evoked potentials, TTS

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