Search PubMed⌕ Search

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.

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

At least 865 records · Page 48Linked to original sources
PubMedDate not supplied

The brain and hearing: auditory discriminations affected by brain lesions.

After bilateral ablation of the auditory areas of the cerebral cortex, experimental animals have a severe deficit in ability to discriminate between temporal patterns of tonal stimuli and to localize sound in space. These two kinds of discrimination are basic for communication and for attack or avoidance of prey and predator. Recognition of which ear is stimulated may also depend upon excitation of auditory cortex contralateral to the given ear. Binaural discriminations are dependent upon interaction of nerve impulses from the two ears at a low level in the auditory nervous system. Similar hearing losses have been reported for human patients.

Animals↗
PubMed2003

Clinical psychoacoustics in Alzheimer's disease central auditory processing disorders and speech deterioration.

BACKGROUND: Difficulty in speech understanding in the presence of background noise or competing auditory signals is typically present in central auditory processing disorders. These disorders may be diagnosed in Alzheimer's disease as a result of degeneration in the central auditory system. In addition perception and processing of speech may be affected. MATERIAL AND METHODS: A MEDLINE research was conducted in order to answer the question whether there is a central auditory processing disorder involved in Alzheimer's disease. A second question to be investigated was what, if any is the connection, between central auditory processing disorders and speech deterioration?Articles were retrieved from the Medline to find relevance of Alzheimer's dis ease with central auditory processing disorders, they summed up to 34. Twelve papers were studied that contained testing for CAPD through psychoacoustic investigation. An additional search using the keywords 'speech production' and 'AD' produced a result of 33 articles, of them 14 are thoroughly discussed in this review as they have references concerning CAPD. The rest do not contain any relavent information on the central auditory system. RESULTS: Psychoacoustic tests reveal significantly lower scores in patients with Alzheimer's disease compared with normal subjects. Tests concerning sound localization and perception of tones as well as phoneme discrimination and tonal memory reveal deficits in Alzheimer's disease. Central auditory processing disorders may exist several years before the onset of clinical diagnosis of Alzheimer's disease. Segmental characteristics of speech are normal. Deficits exist concerning the supra-segmental components of speech. CONCLUSIONS: Central auditory processing disorders have been found in many cases when patients with Alzheimer's disease are tested. They may present as an early manifestation of Alzheimer's disease, preceding the disease by a minimum of 5 and a maximum of 10 years. During these years changes in the central auditory system, starting in the temporal lobe, may produce deficits in speech processing and production as hearing and speech are highly connected human functions. Another theory may be that spread of degeneration of the central nervous system has as a consequence, speech deterioration. Further research and central auditory processing disorders testing in the elderly population are needed to validate one theory over the other.

Journal Article↗
PubMed1992

Application of an implantable bone conduction hearing device to patients with unilateral sensorineural hearing loss.

This investigation, comprised of five studies, was undertaken to determine if individuals with newly acquired profound unilateral hearing losses would benefit from an implantable bone-conduction hearing device. The bone conductor was implanted on the side of the deaf ear at the time of translabyrinthine acoustic tumor resection. Two areas greatly affected by unilateral hearing loss, speech recognition in noise and sound localization, were examined. No improvement in aided performance could be documented in either area.

Adult↗
PubMed1995

Effects of frequency on free-field masking.

As three-dimensional auditory displays become more prevalent, there will be an increasing need to understand the interactions that can be expected among spatially separated sounds. A two-alternative, forced-choice, adaptive staircase procedure was used to measure the detectability of a 165-ms click-train signal masked by a continuous Gaussian noise, as a function of the spatial separation between the signal and the masker in the free field. Horizontal separations within the horizontal plane and vertical separations within the median plane were examined for low-, mid-, and high-frequency stimuli. Masking was reduced by as much as 18 dB when the signal and masker were separated horizontally. Sizable reductions in masking (6-9 dB) were also observed for vertical separations. The largest reductions in masking were observed for the high-frequency stimuli. The data are compared with the results of headphone-based studies of binaural masking. Implications for the design of auditory displays are considered.

Adult↗
PubMed2005

Posthearing developmental refinement of temporal processing in principal neurons of the medial superior olive.

In mammals, principal neurons of the medial superior olive (MSO) exhibit biophysical specializations that enable them to detect sound localization cues with microsecond precision. In the present study, we used whole-cell patch recordings to examine the development of the intrinsic electrical properties of these neurons in brainstem slices from postnatal day 14 (P14) to P38 gerbils. In the week after hearing onset (P14-P21), we observed dramatic reductions in somatic EPSP duration, input resistance, and membrane time constant. Surprisingly, somatically recorded action potentials also dramatically declined in amplitude over a similar period (38 +/- 3 to 17 +/- 2 mV; tau = 5.2 d). Simultaneous somatic and dendritic patch recordings revealed that these action potentials were initiated in the axon, which primarily emerged from the soma. In older gerbils, the rapid speed of membrane voltage changes and the attenuation of action potential amplitudes were mediated extensively by low voltage-activated potassium channels containing the Kv1.1 subunit. In addition, whole-cell voltage-clamp recordings revealed that these potassium channels increase nearly fourfold from P14 to P23 and are thus a major component of developmental changes in excitability. Finally, the electrophysiological features of principal neurons of the medial nucleus of the trapezoid body did not change after P14, indicating that posthearing regulation of intrinsic membrane properties is not a general feature of all time-coding auditory neurons. We suggest that the striking electrical segregation of the axon from the soma and dendrites of MSO principal neurons minimizes spike-induced distortion of synaptic potentials and thus preserves the accuracy of binaural comparisons.

Age Factors↗
PubMed2005

Spectral edge sensitivity in neural circuits of the dorsal cochlear nucleus.

One possible function of the dorsal cochlear nucleus (DCN) is discrimination of head-related transfer functions (HRTFs), spectral cues used for vertical sound localization. Recent psychophysical and physiological studies suggest that steep, rising spectral edges may be the features used to identify HRTFs. Here we showed, using notch noise and noise band stimuli presented over a range of frequencies, that a subclass of DCN type IV neurons responded with a response peak when the rising spectral edge of a notch or band was aligned near best frequency (BF). This edge sensitivity was correlated with weak or inhibited responses to broadband noise and inhibition in receptive fields at frequencies below BF. Some aspects of the inhibition shaping the response peak, namely inhibition to rising edges below BF and to falling edges at BF, could be explained by the properties of type II interneurons with BFs below those of the type IV neurons. However, many type IV neurons also showed inhibitory responses with the rising spectral edge just above BF, and these responses could not be reproduced by current models of DCN circuitry. Therefore, a new component of the DCN circuit is needed to fully explain the responses to rising spectral edges. This shaping of edge sensitivity by inhibition to rising spectral edges both below and above BF suggests the specialization of DCN for spectral edge coding along the tonotopic gradient.

Acoustic Stimulation↗
PubMed2002

Discrimination of individual vocalizations by black-capped chickadees (Poecile atricapilla).

The auditory perceptual abilities of male black-capped chickadees (Poecile atricapilla) were examined using an operant go/no-go discrimination among 16 individual vocalizations recorded at 5 m. The birds learned to discriminate about equally well among eight male chickadee fee-bee songs and eight female zebra finch (Taeniopygia guttata) distance calls. These results do not indicate that chickadees have a species-specific advantage in individual recognition for conspecific over heterospecific vocalizations. We then transferred the chickadees to a discrimination of the same songs and calls rerecorded at a moderate distance. These results showed accurate transfer of discrimination from 16 vocalizations recorded at 5 m to novel versions of the same 16 songs and calls rerecorded at 25 m. That is, chickadees recognized individual songs and calls despite degradation produced by rerecording at 25 m. Identifying individual vocalizations despite their transformation by distance cues is here described as a biologically important example of perceptual constancy.

Animal Communication↗
PubMed2004

Reconsidering evidence for the suppression model of the octave illusion.

The octave illusion is elicited by a sequence of tones presented to each ear that continuously alternate in frequency by one octave, but with high and low frequencies always in different ears. The percept for most listeners is a high pitch in one ear, alternating with a low pitch in the other ear. The influential suppression model of the illusion proposed by Deutsch and Roll (1976) carries three postulates: first, that listeners perceive only the pitch of the tones presented to their dominant ear; second, that this pitch is heard in whichever ear received the higher frequency tone; and third, that this apparent dissociation between what and where mechanisms arises from sequential interactions between the tones. In the present article, we reappraise evidence for the suppression model and demonstrate (1) the incompatibility of the theory with the existing literature on pitch perception, sound localization, and ear dominance and (2) methodological limitations in studies that have claimed to provide support for the suppression model. We conclude by proposing an alternative theory of the octave illusion that is based on established principles of fusion, rather than suppression, between ears.

Auditory Perception↗
PubMed1999

The superior olivary nucleus and its influence on nucleus laminaris: a source of inhibitory feedback for coincidence detection in the avian auditory brainstem.

Located in the ventrolateral region of the avian brainstem, the superior olivary nucleus (SON) receives inputs from nucleus angularis (NA) and nucleus laminaris (NL) and projects back to NA, NL, and nucleus magnocellularis (NM). The reciprocal connections between the SON and NL are of particular interest because they constitute a feedback circuit for coincidence detection. In the present study, the chick SON was investigated. In vivo tracing studies show that the SON projects predominantly to the ipsilateral NM, NL, and NA. In vitro whole-cell recording reveals single-cell morphology, firing properties, and postsynaptic responses. SON neurons are morphologically and physiologically suited for temporal integration; their firing patterns do not reflect the temporal structure of their excitatory inputs. Of most interest, direct stimulation of the SON evokes long-lasting inhibition in NL neurons. The inhibition blocks both intrinsic spike generation and orthodromically evoked activity in NL neurons and can be eliminated by bicuculline methiodide, a potent antagonist for GABAA receptor-mediated neurotransmission. These results strongly suggest that the SON provides GABAergic inhibitory feedback to laminaris neurons. We discuss a mechanism whereby SON-evoked GABAergic inhibition can influence the coding of interaural time differences for sound localization in the avian auditory brainstem.

Animals↗
PubMed1999

Characterization of tuberculo-ventral neurons in the dorsal cochlear nucleus of the guinea pig.

Tuberculo-ventral neurons in the deep polymorphic layer of the dorsal cochlear nucleus of the guinea pig are immunopositive to glycine, their main neurotransmitter, as revealed by post-embedding immunogold. The initial size of gold particles (10-20 nm) was increased (40-70 nm) by silver intensification for a better and rapid individuation of glycine positive cells at low magnification. The most specific ultrastructural characteristic of tuberculo-ventral neurons is their synaptic profile that shows most flat-pleomorphic axo-somatic boutons. This synaptic profile is different from that of other medium size neurons, such as cartwheel neurons in the superficial layer of the dorsal cochlear nucleus. The synaptic profile of tuberculo-ventral neurons together with other characteristics may explain their activity connected to the neural network responsible for echos suppression or/and sound localization.

Animals↗
PubMed2000

Fine-tuning an auditory synapse for speed and fidelity: developmental changes in presynaptic waveform, EPSC kinetics, and synaptic plasticity.

Fast, precise, and sustained synaptic transmission at high frequency is thought to be crucial for the task of sound localization in the auditory brainstem. However, recordings from the calyx of Held synapse have revealed severe frequency-dependent synaptic depression, which tends to degrade the exact timing of postsynaptic spikes. Here we investigate the functional changes occurring throughout the critical period of synapse refinement from immature calyx terminal [postnatal day 5 (P5)] to after the onset of hearing (P12-P14). Surprisingly, for recordings near physiological temperature (35 degrees C), we find that P14 synapses are already able to follow extremely high input rates of up to 800 Hz. This ability stems in part from a remarkable shortening of presynaptic action potentials, which may lead to a lowering of release probability and decrease in synaptic delays during development. In addition, AMPA receptor-mediated EPSCs as well as quantal synaptic currents acquired progressively faster kinetics, although their mean amplitudes did not change significantly. NMDA receptor-mediated EPSCs, however, diminished with age, as indicated by a 50% reduction in mean amplitude and faster decay kinetics. Finally, the degree of synaptic depression was greatly attenuated with age, presumably because of a 2.5-fold or larger increase in the releasable pool of vesicles, which together with a decreasing release probability produces a fairly constant EPSC amplitude. This finely tuned orchestra of developmental changes thus simultaneously promotes speed while preventing premature vesicle pool depletion during prolonged bouts of firing. A few critical days in postnatal development can thus have a large impact on synaptic function.

Action Potentials↗
PubMed2001

High-fidelity transmission acquired via a developmental decrease in NMDA receptor expression at an auditory synapse.

Central auditory relay synapses in mature animals follow high-frequency inputs for computation of sound localization. In immature mice, however, transmission at the calyx of Held synapse in auditory brainstem was inaccurate for high-frequency inputs because the summed slow synaptic potential components caused aberrant firings or blocked action potentials. As the mice matured, synaptic potentials became shorter, with smaller and faster NMDA receptor components, thereby establishing the precise one-to-one transmission for high-frequency inputs. Developmental acquisition of this high-fidelity transmission could be mimicked experimentally in immature mice by blocking NMDA receptors with d(-)2-amino-5-phosphonovaleric acid (d-APV). Furthermore, bilateral cochlear ablations at postnatal day 7 (P7) attenuated the developmental decrease of NMDA receptor expression and prevented the acquisition of high-fidelity transmission. We suggest that auditory activity, which begins at P10-P12 in mice, downregulates the expression of postsynaptic NMDA receptors, thereby contributing to the establishment of high-fidelity synaptic transmission.

2-Amino-5-phosphonovalerate↗
PubMed2001

Maturation of synaptic transmission at end-bulb synapses of the cochlear nucleus.

Neurons of the avian nucleus magnocellularis transmit phase-locked action potentials of the auditory nerve in a pathway that contributes to sound localization based on interaural timing differences. We studied developmental changes in synaptic transmission that enable the end-bulb synapse to function as a synaptic relay. In chick, although the auditory system begins to function early in embryonic development, maturation of audition around the time of hatching suggested that synaptic transmission in the cochlear nucleus of young chicks may undergo further developmental changes. Synaptic physiology was investigated via patch-clamp recordings from bushy cells in brainstem slices during stimulation of auditory nerve fibers at 35 degrees C. Compared with embryonic synapses (embryonic day 18), post-hatch chicks (post-hatch days 1-11) exhibited high probability of firing a well timed postsynaptic action potential during high-frequency stimulation of the auditory nerve. Improvements in reliability and timing of postsynaptic spikes were accompanied by a developmental increase in steady-state EPSCs during stimulus trains and a decline in the extent of synaptic depression. Synchrony of EPSCs during stimulus trains improved with age. An increased pool of synaptic vesicles, lower release probability, larger and faster transmitter quanta, and reduced AMPA receptor desensitization contributed to these changes. Together, these factors improve the ability of cochlear nucleus magnocellularis neurons to faithfully transmit timing information encoded by the auditory nerve.

Action Potentials↗
PubMed2002

[Sensitivity of the neurons in the auditory inferior colliculus of mice to the direction of the shift of broadband spectral notch noise].

Series of a notch noise with regular shifts of the notch center frequency: one--from low frequencies to high frequencies and the other--from high frequencies to the low, were synthesized. The notch noise series imitated sound source vertical moving. Single neuron's responses of inferior colliculus of the house mouse (Mus musculus) to the notch-noises altered with notch central frequency varying through excitatory and inhibitory frequency response areas in neurones' receptive fields. The neural responses alteration to the notch noise varying depended on the bandwidth of notch. Disinhibition in inhibitory side band could be higher if the notch overlying the inhibitory areas followed the notch overlying the excitatory areas. The data obtained make it possible to consider the excitatory and inhibitory interaction as a mechanism of neural sensitivity to the notch moving direction. Neurones' response set could provide information about sound source moving over auditory space.

Acoustic Stimulation↗
PubMed2003

Negative consequences of uncorrected hearing loss--a review.

Hearing loss gives rise to a number of disabilities. Problems in recognizing speech, especially in difficult environments, give rise to the largest number of complaints. Other kinds of disabilities may concern the reduced ability to detect, identify and localize sounds quickly and reliably. Such sounds may be warning or alarm signals, as well as music and birds singing. The communicative disability affects both hearing-impaired people and other people in their environment--family members, fellow workers, etc. Hearing-impaired people are not always aware of all the consequences of the impairment; they do not always know what they are missing. Several studies have shown that uncorrected hearing loss gives rise to poorer quality of life, related to isolation, reduced social activity, and a feeling of being excluded, leading to an increased prevalence of symptoms of depression. These findings indicate the importance of early identification of hearing loss and offers of rehabilitative support, where the fitting of hearing aids is usually an important component. Several studies also point to a significant correlation between hearing loss and loss of cognitive functions. Most of these studies show such a correlation without being able to show whether the hearing loss caused the reduction in cognitive performance or if both the hearing loss and the cognitive decline are parts of a common, general age-related degeneration. A couple of these studies, however, indicate that the uncorrected hearing loss may be the cause of cognitive decline. Whichever alternative is true, the correlation should be seen as a clear indication for early hearing aid fitting for those needing it. Monaural hearing aid fitting in subjects with bilateral hearing loss may give rise to a reduced ability to recognize speech presented to the unaided ear, the so-called late-onset auditory deprivation effect. This functional decline is reversible in some but not all subjects after fitting of a hearing aid also on the previously unaided ear.

Auditory Perceptual Disorders↗
PubMed1992

Intracellular recordings from neurobiotin-labeled cells in brain slices of the rat medial nucleus of the trapezoid body.

Principal cells in the medial nucleus of the trapezoid body (MNTB) are believed to be critical components in the circuit subserving sound localization. These cells, located in the superior olivary complex, convert excitatory inputs, arriving from the contralateral cochlear nucleus by way of large somatic synapses (the calyces of Held), to inhibitory projections onto principal cells in the ipsilateral lateral superior olive (LSO). We have characterized a population of cells in the rat MNTB using intracellular recording and labeling techniques in a brain slice preparation. MNTB principal cells had spherical or ellipsoid somata that gave rise to single large-diameter dendrites, which branched extensively and often extended beyond the borders of MNTB. Commonly observed axonal projection targets included LSO, the superior paraolivary nucleus, and the medial superior olive, and occasionally the lateral nucleus of the trapezoid body. The projections of individual MNTB cells showed an orderly topography that is consistent with the known tonotopic maps of the nuclei. In response to current injection, principal cells exhibited several nonlinearities, including rectification for depolarizing currents and a "sag" in the membrane potential for hyperpolarizing currents. Superthreshold depolarizing currents elicited transient firing behavior. Application of the potassium channel blocker 4-aminopyridine reduced or eliminated the rectification in the current-voltage relationships and caused depolarizing currents to elicit repetitive firing. Stimulation of afferent inputs elicited short-latency spikes, presumably driven by calyceal synaptic inputs; long-latency, presumably polysynaptic, EPSPs; and short- and long-latency IPSPs. The duration of synaptic events was strongly dependent on membrane potential, and this effect was probably due to the intrinsic membrane properties of the cell. In all cases tested, EPSPs were blocked by CNQX or DNQX, and IPSPs were blocked by strychnine. Two injected non-principal cells differed from principal cells in their morphologies and physiological characteristics.

4-Aminopyridine↗
PubMed2003

Two modes of vesicle recycling in the rat calyx of Held.

Vesicle recycling was studied in the rat calyx of Held, a giant brainstem terminal involved in sound localization. Stimulation of brain slices containing the calyx-type synapse with a high extracellular potassium ion concentration in the presence of horseradish peroxidase resulted within several minutes in a reduction of the number of neurotransmitter vesicles and in the appearance of labeled endosome-like structures. After returning to normal solution, the endosome-like structures disappeared over a period of several minutes, whereas simultaneously the number of labeled vesicles increased. A comparison with afferent stimulation suggested that the endosome-like structures normally do not participate in the vesicle cycle. Afferent stimulation at 5 Hz resulted in sustained synaptic transmission, without vesicle depletion but with an estimated endocytotic activity of <0.2 synaptic vesicles per active zone per second. At 20 Hz, the presynaptic action potentials generally failed during prolonged stimulation. In identified synapses, the number of vesicles labeled by photoconversion after stimulation at 5 Hz in the presence of the styryl dye RH414 was much lower than the number of vesicles that were released, as determined by measuring EPSCs. No more than approximately 5% of the vesicles were labeled after 20 min stimulation at 5 Hz, whereas this stimulation protocol was sufficient to largely destain a terminal after previous loading. The results support a scheme for recycling in which two different modes coexist. At physiological demands, a pool of approximately 5% of all vesicles provides sufficient vesicles for release. During intense stimulation, such as occurs in the presence of high extracellular K+, the synapse resorts to bulk endocytosis, a very slow mode of recycling.

Animals↗