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At least 1,009 records · Page 56Linked to original sources
PubMed1979

A study of schizophrenics' ability to localize the source of a sound.

Twelve process, nonparanoid schizophrenics, 12 nonschizophrenic psychiatric controls, and 12 normal controls were given an auditory localization task. Performance was measured by the number of correct localizations and was studied as a function of three variables: diagnosis, position of the apparatus in relation to the subject's median plane (right or left), and the degree of displacement of the auditory stimulus from a fixation point (4.5 degrees, 3.0 degrees, and 1.5 degrees). A three-way analysis of variance with two repeated measures resulted in a significant main effect for each of the three independent variables. Orthogonal comparisons indicated no difference in performance between normal and psychiatric controls but a significant difference between schizophrenics and the combined controls. The degree of displacement of the auditory stimulus resulted in a significant linear trend in performance. There were no significant interactions. The present findings strongly suggest that process, nonparanoid schizophrenics suffer from a specific deficit in auditory localization.

Adult↗
PubMed1988

Interaural transfer of aftereffect of changing sound level in a tone.

Monaural and interaural aftereffects of unidirectional change of sound level in a tone, were measured by a nulling procedure. The former were always much greater than the latter, demonstrating limited interaural transfer of the aftereffect. This is seen as evidence for a peripheral component in the analysis of changing sound level. Such analysis may contribute to the localization of moving sound sources. An additional, and incidental, finding was that a tone without adaptation elicited a perception of steady loudness when its sound level was diminishing slightly. This is consistent with previous evidence.

Adult↗
PubMed1999

Binaural cross-correlation and auditory localization in the barn owl: a theoretical study.

The barn owl is a nocturnal predator that is able to capture mice in complete darkness using only sound to localize prey. Two binaural cues are used by the barn owl to determine the spatial position of a sound source: differences in the time of arrival of sounds at the two ears for the azimuth (interaural time differences (ITDs)) and differences in their amplitude for the elevation (interaural level differences (ILDs)). Neurophysiological investigations have revealed that two different neural pathways starting from the cochlea seem to be specialized for processing ITDs and ILDs. Much evidence suggests that in the barn owl the localization of the azimuth is based on a cross-correlation-like treatment of the auditory inputs at the two ears. In particular, in the external nucleus of the inferior colliculus (ICx), where cells are activated by specific values of ITD, neural activation has been recently observed to be dependent on some measure of the level of cross-correlation between the input auditory signals. However, it has also been observed that these neurons are less sensitive to noise than predicted by direct binaural cross-correlation. The mechanisms underlying such signal-to-noise improvement are not known. In this paper, by focusing on a model of the barn owl's neural pathway to the optic tectum dedicated to the localization of the azimuth, we study the mechanisms by which the ITD tuning of ICx units is achieved. By means of analytical examinations and computer simulations, we show that strong analogies exist between the process by which the barn owl evaluates the azimuth of a sound source and the generalized cross-correlation algorithm, one of the most robust methods for the estimate of time delays.

Journal Article↗
PubMed1994

Localization of swimbladder and pectoral motoneurons involved in sound production in pimelodid catfish.

We localized the motoneurons and occipital and true spinal innervation of sound-producing organs in pimelodid catfish. Pimelodids have a stridulatory organ composed of the pectoral girdle and the first pectoral fin ray, a swimbladder with extrinsic muscles to produce drumming sounds, and a tensor tripodis (TT) muscle that inserts on the swimbladder. Sonic muscles are innervated by three branches (rostral, dorsal and caudal) of the occipital nerve (Oc) and the first two true spinal nerves (S1 and 2): pectoral spine muscles (abductor, adductor and ventral rotator) by the rostral branch of Oc and S1 and 2, drumming muscle by the caudal branch of Oc and twigs of the S1 and 2, and TT by the dorsal branch of Oc. Sonic nuclei from ipsilateral medial, intermediate and ventrolateral columns in the caudal medulla and spinal cord. Pectoral neurons form a ventrolateral motor column, and neurons for the first spine occupy the rostral part of the column. The medial division of the swimbladder drumming motor nucleus (DMm) is situated on the midline between the central canal and the medial longitudinal fasciculus. The rostral pole of the DM nucleus expands ventrolaterally to include a population of neurons of intermediate position (DMi). The TT nucleus also assumes an intermediate position ventrolateral to DMm. The pectoral, TT, and DMi have a restricted rostrocaudal extent, whereas DMm extends further caudally. These data demonstrate that fish can evolve multiple sonic motor nuclei and that sound producing organs can be innervated in parallel by occipital and spinal nerves.

Air Sacs↗
PubMed2006

The ability of the parasitoid fly Ormia ochracea to distinguish sounds in the vertical plane.

The parasitic fly Ormia ochracea localizes its host, field crickets, by homing in on their calling song. Previous phonotactic studies indicate that their sound localization ability in azimuth is extraordinarily acute, but the fly's ability to localize the elevation of sound sources has not been tested to date. Here we show that in a freely-walking closed-loop Y-maze task elevational performance is well above chance, but slightly below the fly's performance in azimuth. Immobilizing the head or the halteres (sensory organs of balance) slightly lowered elevational discrimination, but performance was still well above chance. Because ormiine ears are thought to be symmetric and the pure-tone models of a cricket's call used in these experiments contained little to no spectral bandwidth, additional studies will be needed to elucidate the underlying cues. Nonetheless, it is clear that while walking, Ormia flies are capable of distinguishing sound sources that differ only in elevation.

Animals↗
PubMedDate not supplied

[Localization of a sum of acoustic signals in air by the northern fur seal].

The localization of a sum of acoustic signals by two northern fur seals in air depending on sound parameters was investigated using the method of instrumental conditioned reflexes with food reinforcement. It was found that sound perception of northern fur seal proceeds by the binaural mechanism. The time/intensity interchange coefficient was 570 microseconds/dB for series of clicks (with amplitude maximum at 1 kHz) and 250 microseconds/dB for tonal impulses with a frequency of 1 kHz. With click amplitudes being equal, the number of approaches of the animal to the source of the first signal reached a 75% level at a delay of the second signal 0.07 ms (the minimum delay); with a delay of 6 ms (the maximum delay) and more, the fur seal, probably hears two separate signals. The minimum delay depended little on the duration of tonal impulses (with a frequency of 1 kHz) and was 0.3-0.7 ms; the maximum delay was 9-11 ms for tonal impulses with a duration of 3 ms and 37-40 ms with impulse duration 20 ms. The precedence effect became apparent at a greater delay for smooth fronts of impulses than for rectangular fronts.

Acoustic Stimulation↗
PubMed1985

Vision guides the adjustment of auditory localization in young barn owls.

Barn owls raised with one ear plugged make systematic errors in auditory localization when the earplug is removed. Young owls correct their localization errors within a few weeks. However, such animals did not correct their auditory localization errors when deprived of vision. Moreover, when prisms were mounted in front of their eyes, they adjusted their auditory localization to match the visual error induced by the prisms, as long as the visual and auditory errors were within the same quadrant of directions. The results demonstrate that, during development, the visual system provides the spatial reference for fine-tuning auditory localization.

Animals↗
PubMed1989

The development of a human auditory localization response: a U-shaped function.

Research during the past 10 years on the neonatal head-turn response to off-centred rattle sounds is reviewed, and various procedural and stimulus conditions that influence the probability of eliciting a correct response are identified. Also, the existence of a U-shaped developmental function is confirmed in a cross-sectional study of 104 infants between 3 days and 7 months of age. Neonates responded reliably, but slowly; the response decreased in frequency and magnitude between 1-3 months of age and increased again by 4-5 months of age. Speculation that this U-shaped function reflects a maturational shift in locus of control from subcortical to cortical structures was supported by the infants' responses to the presence effect (PE), which is thought to be cortically mediated. The PE was produced by playing the rattle sound through two loudspeakers with the output of one delayed by 5 ms, relative to the other; adults perceive only one sound at the leading loudspeaker. As predicted, neonates failed to respond to the PE, and the onset of correct PE responses corresponded closely to the upswing in the U-shaped function for SS responses. Other explanations for the temporary decline in orientation responses to sound are also discussed.

Attention↗
PubMed1989

[Ultrasonically-guided transvaginal puncture under local anesthesia for oocyte recovery].

We practised 17 cases of oocyte retrieval between January and June 1988 in our programme of IVF using a vaginal sound and local analgesia in order to retrieve oocytes using a transvaginal ultrasonic guide. The method is described. The recent literature has been reviewed and our results are given: 7.9 oocytes retrieved on an average from each patient, 4.4 oocytes fertilized per patient and 18% of clinical pregnancies. In view of the results that have been obtained and the lessening of risk by avoiding general anaesthesia and the lower cost for each case, as well as the fact that the patients tolerate the method very well, we are now recommending its application routinely and reserve laparoscopy for rare cases.

Adult↗
PubMed2002

Interference effects and phase sensitivity in hearing.

This paper reviews interference effects in the auditory system, particularly effects occurring in the outer ear and the inner ear (cochlea). Sounds enter the ear canal both directly and after reflections from the pinna. This results in complex spectral patterns, which vary systematically with the direction of incidence of the sound source relative to the head. Evidence is described indicating that these spectral patterns are used in the localization of sounds in space. The cochlea behaves like a limited-resolution frequency analyser. When the components of a complex sound are closely spaced in frequency, they can interfere on the basilar membrane (BM) within the cochlea. Interference effects on the BM are complex, as they are influenced by a physiologically active mechanism which introduces strong nonlinearities, including level-dependent amplification. Interference effects on the BM play a role in many aspects of auditory perception, including the perception of consonance and dissonance, the perception of pitch, the perception of changes in phase, and the perception of timbre. Interference effects in the cochlea may also play a role in producing the spectral regularity observed in sounds reflected from the ear (otoacoustic emissions).

Animals↗
PubMed1979

Dynamic auditory localization: systematic replication of the auditory velocity function.

Two experiments explored the capability of normal-hearing adults to judge the apparent velocity of an unseen moving sound source. In exper. I, 9 naive and, 1 experienced S judged the velocity of a moving source emitting a .5-kc/s tone at 50 db SPL. S's head was in the center of a circle of 1.88-m radius swept by a small loudspeaker. In exper. II the sound was a low-pass-filtered (0.1-1 kc/s) noise at 50 db sound spectrum level. In both experiments perceived velocity was directly proportional to the actual velocity of the source. These results support out initial observations (Waugh et al, J. Aud. Res., 1979, 19, 103-1 10) that auditory velocity discrimination can be described as a power function with an exponent of 1.0. In exper. II the Ss also varied the sound source velocity by means of a variable resistor to produce a perceived velocity of 100 degrees/sec. Performance on the adaptive velocity production task was successfully predicted from the data of the absolute velocity judgment task. The Weber fraction was .052 for relatively fast-moving sound sources (100 degrees/sec). The ability to discriminate sound source velocity appears to be a well-defined feature of the dynamic binaural spatial system.

Audiometry↗
PubMed1994

Applications of least-squares FIR filters to virtual acoustic space.

A virtual acoustic space (VAS) employs the localization cues specified by the direction-dependent 'free-field to eardrum transfer function' (FETF) to synthesize sound-pressure waveforms present near the tympanum. The combination of a VAS and the earphone delivery of synthesized waveforms is useful to study parametrically the neural mechanisms of directional hearing. The VAS-earphone procedure requires accurate FETF estimation from free-field measurements and appropriate compensation for the undesirable spectral characteristics of the closed-field earphone sound delivery and measurement systems. Here we describe how specially designed finite-impulse-response (FIR) filters improve these two operations. The coefficients of an FIR filter are determined using a least-squares error criterion. The least-squares FIR filter is implemented entirely in the time domain and avoids the usual problems with division inherent in a frequency domain approach. The estimation of an FETF by a least-squares FIR filter is veracious since its impulse response can recover signals that were recorded near the eardrum in the free field with a very high fidelity. The correlation coefficient between recorded and recovered time waveforms typically exceeds 0.999. Similarly, least-squares FIR filters prove excellent in compensating closed-field sound systems since comparisons of waveforms delivered by a compensated earphone to their corresponding predistorted signals yield correlation coefficients that exceed 0.99 on average.

Acoustic Stimulation↗
PubMed2002

A unified model for the speed of sound in cranial bone based on genetic algorithm optimization.

The density and structure of bone is highly heterogeneous, causing wide variations in the reported speed of sound for ultrasound propagation. Current research on the propagation of high intensity focused ultrasound through an intact human skull for non-invasive therapeutic action on brain tissue requires a detailed model for the acoustic velocity in cranial bone. Such models have been difficult to derive empirically due to the aforementioned heterogeneity of bone itself. We propose a single unified model for the speed of sound in cranial bone based upon the apparent density of bone by CT scan. This model is based upon the coupling of empirical measurement, theoretical acoustic simulation and genetic algorithm optimization. The phase distortion caused by the presence of skull in an acoustic path is empirically measured. The ability of a theoretical acoustic simulation coupled with a particular speed-of-sound model to predict this phase distortion is compared against the empirical data, thus providing the fitness function needed to perform genetic algorithm optimization. By performing genetic algorithm optimization over an initial population of candidate speed-of-sound models, an ultimate single unified model for the speed of sound in both the cortical and trabecular regions of cranial bone is produced. The final model produced by genetic algorithm optimization has a nonlinear dependency of speed of sound upon local bone density. This model is shown by statistical significance to be a suitable model of the speed of sound in bone. Furthermore, using a skull that was not part of the optimization process, this model is also tested against a published homogeneous speed-of-sound model and shown to return an improved prediction of transcranial ultrasound propagation.

Algorithms↗