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Supin AYa

Publications and source records attributed to Supin AYa.

16 recordsLinked to original sources
PubMed2001

Auditory brainstem response recovery in the dolphin as revealed by double sound pulses of different frequencies.

Recovery of auditory brainstem responses (ABR) in a bottlenose dolphin was studied in conditions of double-pip stimulation when two stimuli in a pair differed in frequency and intensity. When the conditioning and test stimuli were of equal frequencies, the test response was markedly suppressed at short interstimulus intervals; complete recovery appeared at intervals from about 2 ms (when two stimuli were of equal intensity) to 10-20 ms (when the conditioning stimulus exceeded the test by up to 40 dB). When the two stimuli were of different frequencies, the suppression diminished and was almost absent at a half-octave difference even if the conditioning stimulus exceeded the test one by 40 dB. Frequency-dependence curves (ABR amplitude dependence on frequency difference between the two stimuli) had equivalent rectangular bandwidth from +/-0.2 oct at test stimuli of 20 dB above threshold to +/-0.5 oct at test stimuli of 50 dB above threshold.

Acoustic Stimulation↗
PubMed1999

Ripple depth and density resolution of rippled noise.

Depth resolution of spectral ripples was measured in normal humans using a phase-reversal test. The principle of the test was to find the lowest ripple depth at which an interchange of peak and trough position (the phase reversal) in the rippled spectrum is detectable. Using this test, ripple-depth thresholds were measured as a function of ripple density of octave-band rippled noise at center frequencies from 0.5 to 8 kHz. The ripple-depth threshold in the power domain was around 0.2 at low ripple densities of 4-5 relative units (center-frequency-to-ripple-spacing ratio) or 3-3.5 ripples/oct. The threshold increased with the ripple density increase. It reached the highest possible level of 1.0 at ripple density from 7.5 relative units at 0.5 kHz center frequency to 14.3 relative units at 8 kHz (5.2 to 10.0 ripple/oct, respectively). The interrelation between the ripple depth threshold and ripple density can be satisfactorily described by transfer of the signal by frequency-tuned auditory filters.

Adult↗
PubMed1998

Lateral suppression of rhythmic evoked responses in the dolphin's auditory system.

In the auditory system of bottlenose dolphins (Tursiops truncatus), a brain-evoked response to rhythmic sound amplitude modulations (the envelope-following response) was markedly suppressed by addition of another sound with a frequency 5-20 kHz higher and an intensity down to 40 dB lower than that of the amplitude-modulated signal. This effect was called paradoxical lateral suppression. This phenomenon was primarily observed when the amplitude-modulated stimulus had a carrier frequency above 30 kHz and modulation rates above 500 Hz. Only the sustained rhythmic response was suppressed, while the transient on-response was not. This indicates that the suppression influenced the ability of evoked potentials to follow rapid amplitude modulations. This prevents weak sounds from being masked by stronger ones.

Acoustic Stimulation↗
PubMed1998

Ripple density resolution for various rippled-noise patterns.

Ripple-density resolution was measured in normal humans using rippled noise with a phase-reversal test. The principle of the test was to find the highest ripple density at which an interchange of spectral peak and trough positions (the phase reversal) is detectable. Different rippled noise patterns were used: (i) either frequency-proportional or constant ripple spacing; (ii) various bandwidth; and (iii) either steep or shallow slopes of the spectrum envelope. When tested with frequency-proportional rippled noise, ripple-density resolution as expressed in relative units (the center frequency to ripple spacing ratio) little depended on frequency within a range of 1 to 8 kHz: from 11.4 at 1 kHz to 14.9 at 8 kHz, mean 13.1. These values were virtually independent on noise bandwidth. When tested with constant ripple spacing, the resolution was of similar values taking the relative ripple density at the lower part of the passband. Being measured by noise with steep spectral edges, the resolution was five units higher than it was for shallow-enveloped spectra, thus suggesting some edge effects at the spectrum boundaries. The resolution values obtained were about twice higher than those predicted by peripheral auditory filter tuning.

Adult↗
PubMed1997

Paradoxical lateral suppression in the dolphin's auditory system: weak sounds suppress response to strong sounds.

A paradoxical phenomenon was found in the auditory system of dolphins: weak sounds suppressed the brain responses to much stronger sounds. This occurred when the brain evoked potentials to rhythmic sound amplitude modulations were recorded. The response was markedly suppressed by addition of another sound of higher frequency and down to 40 dB lower intensity than the amplitude-modulated signal. Only the sustained rhythmic response was suppressed while transient on-response was not, thus indicating that the suppression influenced the ability of evoked potentials to follow rapid amplitude modulations. This prevents weak sounds from being masked by stronger ones. It may help a dolphin to perceive weaker echo-signals in the background of stronger emitted pulses.

Acoustic Stimulation↗
PubMed1997

Frequency-temporal resolution of hearing measured by rippled noise.

Frequency-temporal resolution of hearing was measured in normal hearers using rippled noise stimulation in conjunction with a phase-reversal test. The principle of the test was to interchange peak and trough positions (the phase reversal) and to find the highest ripple density at which such interchange is detectable depending on reversal rate. The measurements were made using narrow-band noises with center frequencies of 0.5-4 kHz. The ripple-density resolution limits were constant at phase-reversal rates below 2-3/s and diminished at higher phase-reversal rates. A model is proposed to explain the data based on the envelope fluctuations inherent in noise; these fluctuations are supposed to limit detection of frequency-temporal sound patterns.

Acoustic Stimulation↗
PubMed1997

Detection of temporal gaps in noise in dolphins: evoked-potential study.

Temporal resolution of hearing was studied in bottlenosed dolphins by recording the auditory brain-stem response (ABR) evoked by gap in noise. Gaps shorter than 0.5 ms evoked a response combining both off- and on-components; longer gaps evoked separate off- and on-responses. Both the response to a short gap and on-response to the end of a long gap increased with increasing gap duration. On-response recovered completely at gap duration of 5-10 ms. Small but detectable response arose at gap duration as short as 0.1 ms. Contrary to the on-response after a long silence, the response to a short gap was less dependent on noise intensity. From these data, the temporal transfer function of the supposed integrator was derived assuming nonlinear transform of the integrator output to ABR amplitude. Equivalent rectangular duration of the found temporal transfer function was 0.27 ms.

Animals↗
PubMed1995

Temporal resolution in the dolphin's auditory system revealed by double-click evoked potential study.

Temporal resolution of hearing in two bottlenosed dolphins was estimated by measuring auditory brain-stem response (ABR) recovery in conditions of double-click stimuli. From these data, temporal transfer function of the supposed integrator was derived assuming nonlinear transform of the integrator output to ABR amplitude. The obtained temporal transfer function showed a nearly constant level up to 200 microseconds. then decay to approximately -3 dB at 300 microseconds (as presented in the sound intensity domain), and subsequent decay of 10-11 dB per time doubling (about 35 dB/decade).

Animals↗
PubMed1995

Ganglion cell topography of the retina in the bottlenosed dolphin, Tursiops truncatus.

The distribution and size of ganglion cells in the retina of the bottlenosed dolphin are described. Ganglion cells concentrate at two spots of the highest density in the nasal and temporal quadrants, 15 to 16 mm (50 to 55 degrees) from the optic disk. The mean peak cell density in both spots is about 670 cells/mm2. With a posterior nodal distance of 14.5 mm (under water), this corresponds to 43 cells/deg2, which provides a retinal resolution of about 9' in water and 12' in air. Mean cell size was from 26 to 31 microns in various parts of the retina.

Animals↗
PubMed1994

Frequency resolving power of the human's hearing.

Frequency resolving power (FRP) of the human's hearing was measured using the rippled noise as a probe. To examine the ripple discrimination, a phase-reversal test was used: the rippled noise was replaced by that with the opposite peak and through positions. This switch can be detected only when rippled structure of the noise spectrum is discriminated. The highest ripple density when the switch was detectable was taken as a FRP measure. Narrow-band rippled spectra were used to measure the FRP within a frequency range of 0.175 to 11 kHz. The highest resolvable ripple density in absolute measure (ripples number per kHz) was about 21/kHz at frequencies below 0.5 kHz and fell down at higher frequencies. Resolvable ripple density in relative measure (central frequency divided by ripple spacing) was about 22 relative units at frequencies above 2.8 kHz and fell down at lower frequencies.

Acoustic Stimulation↗
PubMed1994

Frequency resolving power measured by rippled noise.

Frequency resolving power (FRP) was measured in normal humans using rippled noise with a phase-reversal test. The principle of the test was to find the highest ripple density at which an interchange of mutual peak and trough position (the phase reversal) in the rippled spectrum is detectable. In the frequency range below 0.5 kHz FRP was found to be about 21 ripples per kHz when tested by both broad-band and narrow-band rippled noise. In the frequency range above 2 kHz, FRP measured by the narrow-band rippled noise was 22 to 23 relative units (relation of the noise central frequency to the ripple frequency spacing).

Acoustic Stimulation↗
PubMed1993

Direction-dependent spectral sensitivity and interaural spectral difference in a dolphin: evoked potential study.

Sensitivity and interaural intensity difference (IID) dependence on sound frequency and direction was measured in an Amazon river dolphin Inia geoffrensis by recording the auditory nerve evoked response from the body surface. The maximal sensitivity in the horizontal plane was found when the sound direction was 5 degrees to 10 degrees ipsilateral to the recorded ear; the direction dependence of sensitivity was more pronounced at higher frequencies than at lower ones. The IID reached its peak at small azimuthal angles (7.5 degrees to 15 degrees) and higher sound frequencies (100 kHz), or at large azimuthal angles (30 degrees to 45 degrees) and lower sound frequencies (20 to 30 kHz). Each sound direction featured its specific pattern of spectral sensitivity and of interaural spectral difference. The interaural spectral difference fluctuated within a range of more than 20 dB depending on sound direction. The data indicate that interaural intensity as well as spectral difference may be cues for binaural localization of sound direction by dolphins.

Acoustic Stimulation↗
PubMed1991

Interaural intensity and latency difference in the dolphin's auditory system.

Binaural hearing mechanisms were measured in dolphins (Inia geoffrensis) by recording the auditory nerve evoked response from the body surface. The azimuthal position of a sound source at 10-15 degrees from the longitudinal axis elicited interaural intensity disparity up to 20 dB and interaural latency difference as large as 250 microseconds. The latter was many times greater than the acoustical interaural time delay. This latency difference seems to be caused by the intensity disparity. The latency difference seems to be an effective way of coding of intensity disparity.

Acoustic Stimulation↗
PubMed1990

Auditory brain stem responses in characterization of dolphin hearing.

Auditory brain stem responses (ABR) were recorded from the head surface of non-anesthetized and non-relaxed bottle-nosed dolphins, Tursiops truncatus. The region of best ABR recording was shown to be located 6-9 cm caudal to the blowhole. The threshold values were about 1 mPa for noise bursts and -3 dB re 1 mPa for tone bursts of the optimal frequency (80 kHz). The maximum frequency at which ABR could be evoked was 140 kHz. The duration of temporal summation reached 0.5 ms at intensities near the threshold and decreased with an increase in intensity. When the stimuli were paired clicks of the same intensity, the time to complete recovery from the second response was about 5 ms, while that to its 50% recovery was 0.7 ms. When the conditioning click exceeded the testing one in intensity, prolongation of the recovery period was observed. A 40-dB intensity difference led to an approximately 10-fold prolongation of this period.

Acoustic Stimulation↗
PubMed1986

Evoked potentials of the auditory cortex of the porpoise, Phocoena phocoena.

Evoked potential (EP) recordings in the auditory cortex of the porpoise, Phocoena phocoena, were used to obtain data characterizing the auditory perception of this dolphin. The frequency threshold curves showed that the lowest EP thresholds were within 120-130 kHz. An additional sensitivity peak was observed between 20 and 30 kHz. The minimal EP threshold to noise burst was 3 X 10(-4) - 10(-3) Pa. The threshold for response to modulations in sound intensity was below 0.5 dB and about 0.1% for frequency modulations. Special attention was paid to the dependence of the auditory cortex EP on the temporal parameters of the acoustic stimuli: sound burst duration, rise time, and repetition rate. The data indicate that the porpoise auditory cortex is adapted to detect ultrasonic, brief, fast rising, and closely spaced sounds like echolocating clicks.

Acoustic Stimulation↗