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Biomedical subjects

J A Altman

Publications and source records attributed to J A Altman.

16 recordsLinked to original sources
PubMed1999

Lateralization of a moving auditory image: interrelation of interaural time and intensity differences.

Lateralization of moving fused auditory images (FAIs) was studied under dichotic stimulation, with FAI movement from the right and left ears to midline. The movement was produced by the gradual change of interaural time delay (from +/- 630 to 0 microseconds) in a binaurally presented click train in which a constant interaural intensity difference (IID) between +/- 13 dB was also imposed. The task of the subjects was to show with her/his finger the point on the head surface where the FAI trajectory's ending or starting points were perceived. With IID change within +/- 13 dB, the FAI movement trajectory shifted toward the ear receiving the more intense stimulus. The length of the movement trajectory shortened with IID increase. Functions relating the value of perceived lateral position (Y) of the movement trajectory's ending and starting points to IID value (X) were nearly linear: Y = AX + B. These functions differed in their characteristics whether the movement was to the right versus to the left of midline. They also differed from analogous functions for stationary FAI. At IID = 0 the FAI movement trajectory's endpoint was shifted from midline in the direction of movement. Equivalence ratio for IID and ITD were estimated to be 51 and 29 microseconds/dB respectively for the trajectory's starting and ending points. The IID factor could be several times as effective in moving FAI lateralization as the ITD factor.

Adult↗
PubMed1990

Auditory image movement in evoked potentials.

Long-latency auditory evoked potentials (AEPs) were tested in subjects following binaural stimulation with click trains with gradually changing interaural time delays (delta Ts). With appropriate change of the delta Ts this sound signal could produce the sensation of a moving fused auditory image (FI). It was found that the N1-P2 complex of the AEPs rose in amplitude with the increase of the click rate above 15 Hz, and to a greater extent for the moving than for the unmoved FIs. Binaural release from masking (as measured by the binaural masking level difference (BMLD) for the AEPs) amounted to 6 dB for the unmoved FI. For the moving FI the BMLD for the AEPs amounted to 2.8 and 3.5 dB in men and 13.4 and 11.3 dB in women, for the left and right hemispheres respectively. The amplitude of the N1-P2 complex following stimulation with the 'moving' and 'unmoved' sounds was larger in women than in men.

Adult↗
PubMed1988

Psychophysical characteristics of the auditory image movement perception during dichotic stimulation.

Dichotic stimulation with binaurally presented click trains at time-varying interaural differences of stimulation caused a pronounced sensation of fused image (FI) movement in man. Threshold click rate in the trains needed for the FI movement sensation during variations of interaural time differences of stimulation equalled 7.6 Hz and during variations of interaural intensity differences it equalled 9.6 Hz. When FI movement velocity ranged from about 20 to 120 degrees/s with changing interaural intensity of stimulation, differential threshold for FI movement velocity increased from 2 to 12 degrees/s. Relative differential thresholds of the perception of FI movement velocity were essentially independent of the velocity. Subjective scales of FI movement velocity perception could be basically approximated by linear relations y = AX, y = A(X-X0). The scale slopes appeared to be significantly different during fractionation and multiplication procedures.

Acoustic Stimulation↗
PubMed1987

Lateralization of a moving auditory image in patients with focal damage of the brain hemispheres.

Perception of the moving fused auditory image resulting from dichotic click-train stimulation was studied in 53 patients with focal damages of the temporal lobes. Patients with the right- and left-side damage differed in the click rate for perceived movement and in the movement trajectory length. The data are discussed in connection with right hemisphere specialization for directional hearing.

Adolescent↗
PubMed1986

Role of the dog's auditory cortex in discrimination of sound signals simulating sound source movement.

The ability of seven dogs to discriminate signal simulating sound source movement was studied using the avoidance technique. It was found that dogs can differentiate moving and stationary sound sources, and also discern the direction of the sound source movement. In addition, this study has defined the limits of the conditions under which sound source movement perception occurs. In each dog, unilateral ablation of the auditory cortex was followed by a localization deficit on the side contralateral to the ablation. Bilateral cortical lesions led to complete absence of the ability to discriminate source movement, simulated by changing stimulus interaural time differences. However, the dogs' ability to discriminate the movement after unilateral ablation by detecting interaural intensity differences was preserved, although their discriminative ability was lower than that of intact dogs.

Acoustic Stimulation↗
PubMed1984

Responses of the swimbladder of the carp to sound stimulation.

The oscillations of the swimbladder anterior chamber of the carp (Cyprinus carpio) following stimulation with tones of 300-1500 Hz were studied by the method of holographic interferometry. The oscillation amplitude appeared to be maximal at frequencies close to the resonance frequency of an air bladder of equivalent volume as well as at frequencies corresponding approximately to the second and third harmonics of the resonance frequency. A change in the frequency of the sound signal or in the instantaneous pressure amplitude could result in spatial displacement of the oscillation centers on the swimbladder wall. The interference picture which resulted from recording the swimbladder oscillations over the tested frequency range was not observed on the holograms recorded within 20-24 h after the fish had been killed.

Acoustic Stimulation↗
PubMed1976

Electrical responses of the auditory area of the cerebellar cortex to acoustic stimulation.

Single unit activity from the VI and VII lobuli of the cerebellar vermis cortex was studied following acoustical stimulation with sound signals of different parameters. Cerebellar neurons, as compared to those from the auditory system, showed low selectivity to sound frequency, intensity and duration. However, about 2/3 of the neurons were selectively sensitive to interaural time and intensity differences; about 1/3 of neurons showed a specific response to signals simulating sound motion in a definite direction. Thus, cerebellar neurons seem to be mainly responsive to those sound parameters which are essential for sound localization.

Acoustic Stimulation↗
PubMedDate not supplied

Neuron discharges in the rat auditory cortex during electrical intracortical stimulation.

Studies were carried out in rats anesthetized with ketamine or nembutal, with recording of multicellular activity (with separate identification of responses from individual neurons) in the primary auditory cortex before and after electrical intracortical microstimulation. These experiments showed that about half of the set of neurons studied produced responses to short tonal bursts, these responses having two components-initial discharges arising in response to the sound, and afterdischarge occurring after pauses of 50-100 msec. Afterdischarges lasted at least several seconds, and were generally characterized by a rhythmic structure (with a frequency of 8-12 Hz). After electrical microstimulation, the level of spike activity increased, especially in afterdischarges, and this increase could last up to 4 h. Combined peristimulus histograms, cross-correlations, and gravitational analyses were used to demonstrate interactions of neurons, which increased after electrical stimulation and were especially pronounced in the response afterdischarges.

Acoustic Stimulation↗