SEARCH · Search PubMed

Results for “Sound Localization”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources

PubMed1992

Monaural interaction of excitation and inhibition in the medial superior olive of the mustached bat: an adaptation for biosonar.

In most mammals, the superior olive is the first stage for binaural interaction. Neurons in the medial superior olive (MSO) receive excitatory input from both ears and are sensitive to interaural time or phase differences of low-frequency sounds. The mustached bat (Pteronotus parnellii parnellii), a small echolocating species with high-frequency hearing, probably does not use interaural time or phase differences as cues for sound localization. Although the mustached bat has a large MSO, there is some evidence that it is functionally different from the MSO in nonecholocating mammals. Most MSO neurons in the mustached bat are monaural, excited by a contralateral sound. Their responses are phasic and correlated with either the onset or the offset of a sound. As a first step in determining the origin of these phasic monaural responses, we traced the connections of the MSO by using both retrograde and anterograde transport methods. Excitatory inputs to the MSO originate from spherical cells in the anteroventral cochlear nucleus, almost exclusively from the contralateral side. Glycinergic inhibitory input is relayed from the contralateral cochlear nucleus through the medial nucleus of the trapezoid body. To investigate the interactions of the contralateral excitatory and inhibitory inputs at the level of the MSO cell, we recorded sound-evoked responses and applied glycine or its antagonist by using microiontophoresis. The results show that the phasic response to a contralateral sound is created by interaction of a sustained excitatory input with a sustained inhibitory input, also from the contralateral ear. Whether the response is to the onset or offset of a sound is determined by the relative timing between the excitatory and inhibitory inputs. Thus, in MSO of the mustached bat, the ipsilateral excitatory pathway from the cochlear nucleus seen in animals with low-frequency hearing is virtually absent, and the MSO is adapted for timing analysis by using input from only the contralateral ear.

Action Potentials↗

PubMed2000

On cortical coding of vocal communication sounds in primates.

Understanding how the brain processes vocal communication sounds is one of the most challenging problems in neuroscience. Our understanding of how the cortex accomplishes this unique task should greatly facilitate our understanding of cortical mechanisms in general. Perception of species-specific communication sounds is an important aspect of the auditory behavior of many animal species and is crucial for their social interactions, reproductive success, and survival. The principles of neural representations of these behaviorally important sounds in the cerebral cortex have direct implications for the neural mechanisms underlying human speech perception. Our progress in this area has been relatively slow, compared with our understanding of other auditory functions such as echolocation and sound localization. This article discusses previous and current studies in this field, with emphasis on nonhuman primates, and proposes a conceptual platform to further our exploration of this frontier. It is argued that the prerequisite condition for understanding cortical mechanisms underlying communication sound perception and production is an appropriate animal model. Three issues are central to this work: (i) neural encoding of statistical structure of communication sounds, (ii) the role of behavioral relevance in shaping cortical representations, and (iii) sensory-motor interactions between vocal production and perception systems.

Animal Communication↗

PubMed2006

The evidence base for the application of contralateral bone anchored hearing aids in acquired unilateral sensorineural hearing loss in adults.

. Acquired unilateral sensorineural hearing loss reduces the ability to localize sounds and to discriminate in background noise. . Four controlled trials attempt to determine the benefit of contralateral bone anchored hearing aids over contralateral routing of signal (CROS) hearing aids and over the unaided condition. All found no significant improvement in auditory localization with either aid. Speech discrimination in noise and subjective questionnaire measures of auditory abilities showed an advantage for bone anchored hearing aid (BAHA) > CROS > unaided conditions. . All four studies have material shortfalls: (i) the BAHA was always trialled after the CROS aid; (ii) CROS aids were only trialled for 4 weeks; (iii) none used any measure of hearing handicap when selecting subjects; (iv) two studies have a bias in terms of patient selection; (v) all studies were underpowered (vi) double reporting of patients occurred. . There is a paucity of evidence to support the efficacy of BAHA in the treatment of acquired unilateral sensorineural hearing loss. Clinicians should proceed with caution and perhaps await a larger randomized trial. . It is perhaps only appropriate to insert a BAHA peg at the time of vestibular schwanoma tumour excision in patients with good preoperative hearing, as their hearing handicap increases most.

Auditory Threshold↗

PubMed1989

Theoretical criterion for acoustic aggregation.

Theory was given previously for the radiation force between two spherical particles immersed in a fluid and subjected to a sound field. From this theory an expression has been obtained for the effective energy of interaction. A minimum energy, defining a "binding energy" Wmin, occurs when the particles are in contact and aligned with their line of centers perpendicular to the oscillatory motion in the local sound field. When Wmin is large enough, dimers are formed which combine to build larger aggregates. A criterion for aggregation was obtained, similar to one arrived at by Schwan for aggregation produced by alternating electric fields, by setting Wmin equal to the thermal energy kT. Calculations suggest that aggregation of blood cells may occur during applications of medical ultrasound under some conditions. Experiments are needed to test possibilities.

Cell Aggregation↗

PubMed1996

Age-related loss of activity of auditory-nerve fibers.

1. Characteristic frequencies (CF), spontaneous rates (SR), and thresholds were recorded from single fibers in the auditory nerves of gerbils aged for 36 mo in a quiet vivarium. The data from the quiet-aged animals were compared with similar data obtained previously from young controls. Fibers were classified as "low-SR" if their spontaneous rates were < or = 18 spikes/s and "high SR" for higher rates. 2. For CFs > 6 kHz, the percentage of low-SR fibers contacted declined from 57% of the population in young gerbils to 29% in the aged gerbils. This population change is statistically significant (P < 0.01). At CFs < 6 kHz, the population demographics did not change significantly with age, with the low-SR fibers comprising 30 and 39% of the population, respectively, for the young and aged animals. 3. To further test the hypothesis that low-SR fibers with CFs > 6 kHz become less active with age, additional experiments were conducted to examine the recovery of the compound action potential (CAP) response from prior high-level stimuli. Previous work has shown that the CAP recovery curve has two segments: a fast segment associated with the high-SR fibers and a slow segment associated with the low-SR fibers. The curves obtained from quiet aged gerbils show a faster recovery than young controls for probe tones at 8 and 16 kHz, but not at 2 and 4 kHz. Thus these results agree with our single-fiber data indicating that there is a loss of low-SR activity for CFs > 6 kHz in the aged animals. 4. Low-SR fibers typically have larger dynamic ranges than those of high-SR fibers, are better able to preserve information concerning stimulus timing and amplitude modulation, and their responses are more robust in the presence of masking noise. Moreover, low-SR fibers are likely inputs to the crossed-olivocochlear reflex, a reflex that serves an antimasking role in the detection of sounds in a binaural noise field. If true for humans, the loss of the low-SR system could explain many of the hearing deficits often seen in older individuals; e.g., decreased ability to understand speech in noise, changes in masking level differences, and decreased ability to localize sound sources using binaural cues.

Acoustic Stimulation↗

PubMedDate not supplied

Auditory processing in patients with temporal lobe epilepsy.

UNLABELLED: Temporal epilepsy, one of the most common presentation of this pathology, causes excessive electrical discharges in the area where we have the final station of the auditory pathway. Both the anatomical and functional integrity of the auditory pathway structures are essential for the correct processing of auditory stimuli. AIM: to check the Auditory Processing in patients with temporal lobe epilepsy regarding the auditory mechanisms of discrimination from sequential sounds and tone patterns, discrimination of the sound source direction and selective attention to verbal and nonverbal sounds. METHOD: eight individuals with temporal lobe epilepsy were assessed, after excluding those with non-confirmed diagnosis or with the focus of discharges not limited to this lobe. The evaluation was carried out through special auditory tests: Sound Localization Test, Duration Pattern Test, Digits Dichotic Test and Non-Verbal Dichotic Test. Their performances were compared to the performances of individuals without neurological diseases (case-control study). RESULTS: similar performances were observed between patients with temporal lobe epilepsy and the control group regarding the auditory mechanism of sound source direction discrimination. Comparing the other auditory mechanisms assessed, the patients with temporal lobe epilepsy presented worse results. CONCLUSION: individuals with temporal lobe epilepsy had more deficits in auditory processing than those without cortical damage.

Acoustic Stimulation↗

PubMed1991

Central auditory processing disorder: a case study.

We carried out extensive audiologic, electrophysiologic, and neuropsychologic testing on a young woman who complained that she had difficulty hearing in her educational environment. Conventional audiometric results, including pure-tone, speech, and immittance audiometry, were all within normal limits. The subject performed normally on tests involving the processing of rapidly changing temporal information, interaural time and intensity difference detection, and both absolute and relative sound localization. Early, middle, late and task-related auditory evoked potentials were essentially normal, although some asymmetry was observed in the middle latency (MLR) and late (LVR) responses. There was, however, a consistent left-ear deficit on dichotic sentence identification, on threshold and suprathreshold speech measures in the left sound field when various types of competition were delivered in the right sound field, and on cued-target identification in the left sound field in the presence of multitalker babble. Results suggest a central auditory processing disorder characterized by an asymmetric problem in the processing of binaural, noncoherent signals in auditory space. When auditory space was structured such that the target was directed to the left ear, and the competition to the right ear, unwanted background was less successfully suppressed than when the physical arrangement was reversed.

Acoustic Impedance Tests↗

PubMed2000

Directional hearing of a grasshopper in the field.

An electrophysiological method for making long-term recordings from the tympanal nerve was developed in Chorthippus biguttulus (Gomphocerinae) to gain insight into the ecophysiological constraints of sound localization in acridid grasshoppers. Using this 'biological microphone', the directional dependence of auditory nerve activity was monitored both in the laboratory and in various natural habitats of this species. On gravel and in sparse vegetation, the overall patterns of directionality were found to be very similar to those in the free sound field in the laboratory, regardless of whether the animal was positioned horizontally or vertically. However, the differences between the ipsi- and contralateral sides were smaller in these habitats than in the laboratory. In dense vegetation, the directional patterns were greatly affected by the environment. Moreover, a minimum in nerve activity was not always reached on the contralateral side, as is typical for the free sound field situation. On the basis of these data, predictions can be made about the ability of the animals to determine the correct side of a sound source. In the free sound field of the laboratory, correct lateralizations are expected at all angles of sound incidence between 20 and 160 degrees, a prediction corresponding to the results of behavioural studies. In sparse vegetation, a similar accuracy can be anticipated, whereas on gravel and in dense vegetation directional hearing is expected to be severely degraded, especially if the animal is oriented horizontally. The predictions from our present electrophysiological investigations must now be confirmed by behavioural studies in the field.

Animals↗

PubMed1970

Directional hearing: effect of unilateral change of the sound duration.

Monaural change of the duration of a binaural acoustic stimulus within the range of 0.5 to 1.5 milliseconds caused a considerable shift of the sound image. This could be counterbalanced by a unilateral change of the signal intensity. Further unilateral lengthening of the stimulus did not affect the sound localization, but it revealed a masking aftereffect (4 to 10 milliseconds) of the binaural signal. The data define the temporal characteristics of binaural effect influenced the binaural interaction.

Auditory Threshold↗

PubMed1995

Localization of knee joint cartilage pathology by multichannel vibroarthrography.

This paper proposes non-invasive techniques to localize sound or vibroarthrographic (VAG) signal sources in human knee joints. VAG signals from normal subjects, patients who subsequently underwent arthroscopy, and cadavers with arthroscopically-created lesions, obtained by stimulation with a finger tap over the mid-patella and swinging movement of the leg, were analyzed for time delays using cross-correlation functions for source localization. Correct results were obtained for 13 of the 14 subjects tested by finger stimulation, and for 11 of the 12 subjects whose VAG signals during swinging movement were analyzed. The techniques could be valuable in the diagnosis and treatment of knee pathology before and after joint surgery or drug therapy.

Arthroscopy↗

PubMed1976

Single unit study of binaural interaction in the auditory cortex of the chinchilla.

The primary aim of this investigation was to systematically compare for various stimulus conditions the relative influences of contralateral and ipsilateral acoustic stimulation on cortical single units in an unanesthetized preparation and to study the effects upon single unit responses of the dominant stimulus cues for sound localization--interaural intensity difference (deltaI) and interaural time difference (deltat). Recordings were obtained from 133 units in chinchillas immobilized by gallamine triethiodide. All units were found to be influenced by input from both ears. Unit thresholds for contralateral stimulation were lower and more discharges were elicited than for ipsilateral stimulation over a range of intensities from unit threshold intensity to 80 dB sound-pressure level. A predominance of contralateral influence was also observed when the number of stimulus-evoked discharges was plotted as a function of the deltaI or deltat. For 62% of the deltaI functions maximal responsiveness occurred for binaural stimuli that were more intense at the contralateral ear. Similarly, of the 36 units that showed sensitivity to deltat parameters for tone stimuli, 22 (61%) were maximally responsive at the contralateral-leading deltat intervals. For click stimuli, maximal responsiveness for all 21 deltat-sensitive units also occured for contralateral-leading stimuli. Certain observations in the study question the generality of the hypothesis that a particular cell invariantly encodes a specific deltat, i.e., that cells have 'characteristic delays'. First, most units tested at more than two frequencies showed maximal responsiveness at different deltat intervals depending upon stimulus frequency. Second, the deltat intervals for maximal responsiveness for half of the units tested were greater than the maximal interaural delays the animal could encounter naturally. Third, deltat functions from the same unit for click and tone stimuli showed poor correspondence. These findings suggest that the encoding of interaural time and intensity might depend on an inter-hemispheric comparison of the activity of neural populations as originally proposed by von Bekesy.

Acoustic Stimulation↗

PubMed2001

The shape of ears to come: dynamic coding of auditory space.

In order to pinpoint the location of a sound source, we make use of a variety of spatial cues that arise from the direction-dependent manner in which sounds interact with the head, torso and external ears. Accurate sound localization relies on the neural discrimination of tiny differences in the values of these cues and requires that the brain circuits involved be calibrated to the cues experienced by each individual. There is growing evidence that the capacity for recalibrating auditory localization continues well into adult life. Many details of how the brain represents auditory space and of how those representations are shaped by learning and experience remain elusive. However, it is becoming increasingly clear that the task of processing auditory spatial information is distributed over different regions of the brain, some working hierarchically, others independently and in parallel, and each apparently using different strategies for encoding sound source location.

Journal Article↗

PubMed2003

Binaural sensitivity as a function of interaural electrode position with a bilateral cochlear implant user.

Experiments were conducted with a single, bilateral cochlear implant user to examine interaural level and time-delay cues that putatively underlie the design and efficacy of bilateral implant systems. The subject's two implants were of different types but custom equipment allowed presentation of controlled bilateral stimuli, particularly those with specified interaural time difference (ITD) and interaural level difference (ILD) cues. A lateralization task was used to measure the effect of these cues on the perceived location of the sensations elicited. For trains of fixed-amplitude, biphasic current pulses at 100 pps, the subject demonstrated sensitivity to an ITD of 300 micros, providing evidence of access to binaural information. The choice of bilateral electrode pair greatly influenced ITD sensitivity, suggesting that electrode pairings are likely to be an important consideration in the effort to provide binaural advantages. The selection of bilateral electrode pairs showing sensitivity to ITD was partially aided by comparisons of the pitch elicited by individual electrodes in each ear (when stimulated alone with fixed-amplitude current pulses at 813 pps): specifically, interaural electrodes with similar pitches were more likely (but not certain) to show ITD sensitivity. Significant changes in lateral position occurred with specific electrode pairs. With five bilateral electrode pairs of 14 tested, ITDs of 300 and 600 micros moved an auditory image significantly from right to left. With these same pairs, ILD changes of approximately 11% of the dynamic range (in microApp) moved an auditory image from the far left to the far right-significantly farther than the nine pairs not showing significant ITD sensitivity. However, even these nine pairs did show response changes as a function of the interaural (or confounding monaural) level cue. Overall, insofar as the access to bilateral cues demonstrated herein generalizes to other subjects, it provides hope that the normal binaural advantages for speech recognition and sound localization can be made available to bilateral implant users.

Acoustic Stimulation↗

PubMed2003

Blind estimation of reverberation time.

The reverberation time (RT) is an important parameter for characterizing the quality of an auditory space. Sounds in reverberant environments are subject to coloration. This affects speech intelligibility and sound localization. Many state-of-the-art audio signal processing algorithms, for example in hearing-aids and telephony, are expected to have the ability to characterize the listening environment, and turn on an appropriate processing strategy accordingly. Thus, a method for characterization of room RT based on passively received microphone signals represents an important enabling technology. Current RT estimators, such as Schroeder's method, depend on a controlled sound source, and thus cannot produce an online, blind RT estimate. Here, a method for estimating RT without prior knowledge of sound sources or room geometry is presented. The diffusive tail of reverberation was modeled as an exponentially damped Gaussian white noise process. The time-constant of the decay, which provided a measure of the RT, was estimated using a maximum-likelihood procedure. The estimates were obtained continuously, and an order-statistics filter was used to extract the most likely RT from the accumulated estimates. The procedure was illustrated for connected speech. Results obtained for simulated and real room data are in good agreement with the real RT values.

Acoustics↗

PubMed1997

Phase locking to high frequencies in the auditory nerve and cochlear nucleus magnocellularis of the barn owl, Tyto alba.

The auditory system of the barn owl is an important model for temporal processing on a very fast time scale and for the neural mechanisms and circuitry underlying sound localization. Phase locking has been shown to be the behaviorally relevant temporal code. This study examined the quality and intensity dependence of phase locking in single auditory nerve fibers of the barn owl to define the input to the known brainstem circuit for temporal processing. For direct comparison in the same individuals, recordings were also obtained from the relevant next higher center, the nucleus magnocellularis (NM). Phase locking was regularly seen at sound pressure levels (SPL) below those eliciting an increase in spike rate, thus providing an additional cue for signal detection. The quality of phase locking, expressed as vector strength, decreased with increasing frequency. Auditory nerve fibers showed an unusual step-like decline with a prominent plateau in the mid-frequency range (1.5-3 kHz), indicating that some specialization enables the owl to halt the deterioration and extend phase locking to frequencies up to 10 kHz, above the range commonly observed in other species. Phase locking in the NM was consistently inferior to that of auditory-nerve fibers at frequencies above 1 kHz, suggesting that the synapse plays a limiting role in temporal precision. The response delays, or group delays, derived from the phase-versus-frequency functions of auditory nerve fibers were not consistent with the unusual spatial frequency representation in the owl cochlea. This questions the common assumption that group delays reflect cochlear wave travel times.

Acoustic Stimulation↗

PubMed2002

Monaural and binaural processing in the ventral nucleus of the lateral lemniscus: a major source of inhibition to the inferior colliculus.

The ventral nucleus of the lateral lemniscus (VNLL) is a major source of input to the inferior colliculus. This paper reviews recent studies of neural responses in the VNLL of the unanesthetized rabbit. The VNLL has generally been viewed as a monaural nucleus, with its neurons responding primarily to stimulation of the contralateral ear. In the rabbit, the VNLL is divided into a medial division (VNLLm) comprising neurons intercalated in the medial limb of the lemniscus, a compact lateral division (VNLLl), and a dorsal division. The VNLLm contains an abundance of neurons sensitive to interaural temporal disparities (ITDs), one of the major binaural cues for sound localization. These neurons respond only at the onset of tones, and therefore appear to encode the ITDs of transients. Even in the VNLLl, many neurons are sensitive to binaural stimulation. The VNLLl contains a variety of neurons with different discharge patterns, the two most common of which are sustained and onset. The discharge patterns, frequency-tuning and dynamic ranges of VNLLl neurons indicate that this division is able to supply the inferior colliculus with a variety of inputs, each serving a different function in the analysis of sound.

Acoustic Stimulation↗

PubMed1990

Delay-tuned neurons in auditory cortex of mustached bat are not suited for processing directional information.

1. The mustached bat, Pteronotus parnellii parnellii, emits bisonar pulses each consisting of eight components: CF1-4 and FM1-4. In the auditory cortex of the bat there are arrays of FM-FM neurons that are tuned to particular delays of echo FMn (n = 2, 3, or 4) from pulse FM1. They are specialized for the processing of target-range information. The FM signal is suited for ranging and also for target localization. Therefore we studied the directional sensitivity of FM-FM neurons with pulse FM1 and echo FMn. One of the FM1-FMn pair was moved around the bat's head while the other was fixed in front of the bat. 2. FM-FM neurons are sharply tuned in echo delay and are broadly tuned in echo amplitude. That is, they are tuned to a target that has a particular cross-sectional area and that is located at a particular distance from the bat. Their best amplitudes for echoes range between 8 and 73 dB sound pressure level (SPL). The best amplitude is approximately 30 dB higher than minimum threshold in the majority of neurons. 3. The higher the best amplitude is relative to minimum threshold, the larger the receptive field is at the best amplitude. The receptive field of FM-FM neurons at 30 dB above minimum threshold is always so large that it covers the entire contralateral auditory field or the entire contralateral field and the medial half of the ipsilateral auditory field. The large size of the receptive field and the uniform distribution of response magnitudes within the receptive field indicate that FM-FM neurons are not suited for sound localization. Directional information is probably processed in parallel by a separate population of neurons other than FM-FM neurons. 4. The receptive field of FM-FM neurons at 10 dB above minimum threshold is much smaller than that at 30 dB above minimum threshold, but it is still large. The mean azimuthal and elevational widths for echo FMn are greater than 70 degrees in all directions. There is no sign that FM-FM neurons are more directional than peripheral neurons. Furthermore, there is neither an azimuthal nor an elevational axis within the FM-FM area. 5. Mean best azimuths of FM-FM neurons are different for each echo FM harmonic: lateral 35 degrees for FM2 and lateral 19 degrees for FM3 and FM4.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗

PubMed1978

Two determinants of localization acuity in the horizontal plane.

An attempt was made to extend the auditory localization model of Searle, Braida, Davis, and Colburn [J. Acoust. Soc. Am. 60, 1164-1175 (1976)] to regions beyond the fontal horizontal plane. On the basis of two experiments, it appears that the assumption of acuity independent of angle is not valid for these more extensive regions, although the distribution of error magnitude can be accounted for by a span-specific unitary acuity. However, the assertion by the same authors that acuity is partially determined by the angular size of the speaker span was substantiated by direct experimental test. The results confirm the initial suggestion of Searle et al. that a complete account of the sound localization process must include both span and angular dependencies of acuity, and indicate average error to be a promising measurement technique in resolving this particular problem.

Auditory Perception↗