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At least 937 records · Page 52Linked to original sources
PubMed2001

[Central hyperacusis with phonophobia in multiple sclerosis].

Auditory disturbances are a well known symptom in patients with multiple sclerosis (MS). Uni- or bilateral hypacusis or deafness in patients with normal auditory testing is considered to be a result of lesions in the central auditory pathway. Only rarely described is a central phonophobia whereby acoustic stimuli induce unpleasant and painful perceptions, with consecutive avoidance of these factors. Our first patient described acute shooting pain in the right cheek, triggered only through the ringing of a telephone. The second patient had uncomfortable perception of nonverbal noise. For example the wrinkling of paper bags was unbearable for him. The third patient had difficulties localizing the source of sound and disturbing echos while listening to speech or music. Clinically, in all patients symptoms of a brainstem syndrome were found, whereas auditory testing including inspection, audiometry, and stapedius reflex was normal. We found pathological acoustic evoked potentials (AEP) in all three patients with a prolonged latency III-V and T2 lesions in the ipsilateral pons and central auditory pathway. In case one, we suppose a lateral spread between the lateral lemniscus and the central trigeminal pathway. In the other cases, a dysfunction of the central sensory modulation which controls the regulation of sensitivity of incoming acoustic stimuli seems to be the cause of hyperacusis. All our patients developed clinically confirmed MS in the further course after suffering from phonophobia as their first symptom.

Acoustic Stimulation↗
PubMed2006

The influence of the perceptual or fear learning on rats' prepulse inhibition induced by changes in the correlation between two spatially separated noise sounds.

Perceptually grouping a sound source with its reflections and separating them from irrelevant background noise sounds need computation of sound correlations and are critical for identifying and localizing the sound source in a complex acoustic environment. Using the prepulse inhibition of the acoustic startle reflex (ASR) as a measure, the present study investigated whether rats are able to detect correlation changes between sounds from different spatial locations. The results show that the rat's ASR amplitude was suppressed when the startle-eliciting stimulus was preceded by either an uncorrelated noise fragment or an anti-phase noise fragment that was embedded in two identical (correlated) but spatially separated noises. Suppression of the ASR amplitude increased as the duration of the noise fragment increased from 5ms to 40ms. The suppressive effect was also progressively enhanced after rats underwent successive testing sessions. Moreover, an enhanced suppression of the ASR amplitude was observed after rats were exposed to footshock that was precisely paired with a 100-ms correlation-change fragment. The results indicate that rats are able to detect the correlation change between sounds from two separated spatial locations, and the detection can be facilitated by both perceptual learning and emotional learning.

Acoustic Stimulation↗
PubMed1986

[Auditory localization and speech perception in noise. Preliminary study concerning 5 cases of perceptual deafness].

The experiments reported here examine the psychoacoustical bases for poor speech perception in noise by persons with sensorineural impairment. Two major hypotheses are tested. First, because persons with cochlear impairment are less able than normal-hearing persons to separate out incoming signals on the basis of spectral differences (a deficit referred to as reduced frequency selectivity), they are less able to localize one sound in the presence of other sounds. Second, this reduced localization ability makes it difficult for the hearing-impaired person to take advantage of the spatial separation of a target speech source and other interfering sources. Such separation is common in real environments and facilitates speech perception by normal-hearing persons. Tests of these hypotheses are conducted by means of detailed psychoacoustical measures of frequency selectivity, of localization and speech perception under masking.

Adolescent↗
PubMed1998

Sensitivity to interaural time differences in the medial superior olive of a small mammal, the Mexican free-tailed bat.

Neurons in the medial superior olive (MSO) are thought to encode interaural time differences (ITDs), the main binaural cues used for localizing low-frequency sounds in the horizontal plane. The underlying mechanism is supposed to rely on a coincidence of excitatory inputs from the two ears that are phase-locked to either the stimulus frequency or the stimulus envelope. Extracellular recordings from MSO neurons in several mammals conform with this theory. However, there are two aspects that remain puzzling. The first concerns the role of the MSO in small mammals that have relatively poor low-frequency hearing and whose heads generate only very small ITDs. The second puzzling aspect of the scenario concerns the role of the prominent binaural inhibitory inputs to MSO neurons. We examined these two unresolved issues by recording from MSO cells in the Mexican free-tailed bat. Using sinusoidally amplitude-modulated tones, we found that the ITD sensitivities of many MSO cells in the bat were remarkably similar to those reported for larger mammals. Our data also indicate an important role for inhibition in sharpening ITD sensitivity and increasing the dynamic range of ITD functions. A simple model of ITD coding based on the timing of multiple inputs is proposed. Additionally, our data suggest that ITD coding is a by-product of a neuronal circuit that processes the temporal structure of sounds. Because of the free-tailed bat's small head size, ITD coding is most likely not the major function of the MSO in this small mammal and probably other small mammals.

Acoustic Stimulation↗
PubMed1999

Auditory cortical responses in the cat to sounds that produce spatial illusions.

Humans and cats can localize a sound source accurately if its spectrum is fairly broad and flat, as is typical of most natural sounds. However, if sounds are filtered to reduce the width of the spectrum, they result in illusions of sources that are very different from the actual locations, particularly in the up/down and front/back dimensions. Such illusions reveal that the auditory system relies on specific characteristics of sound spectra to obtain cues for localization. In the auditory cortex of cats, temporal firing patterns of neurons can signal the locations of broad-band sounds. Here we show that such spike patterns systematically mislocalize sounds that have been passed through a narrow-band filter. Both correct and incorrect locations signalled by neurons can be predicted quantitatively by a model of spectral processing that also predicts correct and incorrect localization judgements by human listeners. Similar cortical mechanisms, if present in humans, could underlie human auditory spatial perception.

Animals↗
PubMed2000

Working memory of auditory localization.

To investigate brain mechanisms of sound location memory, we studied the distribution of brain activation with functional magnetic resonance imaging (fMRI) in subjects performing an audiospatial n-back task with three memory load levels. Working memory processing of audiospatial information activated areas in the superior, middle and inferior frontal gyri, and in the posterior parietal and middle temporal cortices. In a control experiment, fMRI during audio- and visuospatial 2-back task performances revealed only few differentially activated subregions between the two tasks. These results demonstrate that working memory processing of auditory locations involves a distributed network of brain areas and suggest that mnemonic processing of audio- and visuospatial information is directed along a common neural pathway in the posterior parietal and prefrontal cortices.

Acoustic Stimulation↗
PubMed2001

Simultaneously active pre-attentive representations of local and global rules for sound sequences in the human brain.

Regular sequences of sounds (i.e., non-random) can usually be described by several, equally valid rules. Rules allowing extrapolation from one sound to the next are termed local rules, those that define relations between temporally non-adjacent sounds are termed global rules. The aim of the present study was to determine whether both local and global rules can be simultaneously extracted from a sound sequence even when attention is directed away from the auditory stimuli. The pre-attentive representation of a sequence of two alternating tones (differing only in frequency) was investigated using the mismatch negativity (MMN) auditory event-related potential. Both local- and global-rule violations of tone alternation elicited the MMN component while subjects ignored the auditory stimuli. This finding suggests that (a) pre-attentive auditory processes can extract both local and global rules from sound sequences, and (b) that several regularity representations of a sound sequence are simultaneously maintained during the pre-attentive phase of auditory stimulus processing.

Acoustic Stimulation↗
PubMed1989

On the minimum audible angle--a decision theory approach.

The minimum audible angle (MAA) technique is a well-known psychoacoustical paradigm often used in the study of localization of sound. A difficulty with this paradigm, however, is that, in terms of decision theory, it is subject to two quite different interpretations. Although it is normally regarded as involving a discrimination task, the present work suggests that it is more likely to be an absolute identification task. Because of this difference in interpretation, it appears that previous work has overestimated the ability of listeners to localize sources of sound.

Acoustic Stimulation↗
PubMed1986

Development of auditory localization in dogs: single source and precedence effect sounds.

The development of auditory localization in dogs was investigated in a litter of 12 pups. Behavioral auditory localization consisted of orienting responses to dog vocalizations presented from loudspeakers 90 degrees to each side. Sounds were presented in two configurations, single source (only one loudspeaker) and precedence effect (both loudspeakers, with one slightly leading the other). Localization began around 16 days after birth, for single-source sounds. This is consistent with previous observations and with findings on dogs' auditory neural development. Single-source sounds were localized earlier during development than precedence-effect sounds. This ordering resembles findings on human infants and can be related to neuroanatomical investigations of mammalian brain structures mediating single source versus precedence effect localization.

Age Factors↗
PubMed2005

Foreign body aspiration in children.

BACKGROUND: The aim was to investigate the role of physical and radiological findings before bronchoscopy in the diagnosis of foreign body aspiration (FBA). METHODS: We retrospectively reviewed the clinical records for 82 patients (mean age 26.4 +/- 21.4 months, range 9 months to 13.5 years; 49 males) with a history suggestive of foreign body aspiration. RESULTS: The presence of a foreign body in the airways was confirmed in 70 children (85.4%) (mean age 25 +/- 14.1 months, 45 boys). Of the 70 children, 63 patients (90%) were under 3 years of age, with a peak incidence during the second year. Of the 70 foreign bodies retrieved, 46 (60%) were vegetable and 35 (76%) of these were nuts. In 42% of the patients the foreign body was located in the right bronchial tree. The most frequent physical findings observed in our patients were persistent cough (75%), localized decreased breath sound (62.8%) and localized wheezing (30%). The clinical triad (concomitant cough, localized wheezing and decreased breath sound) was present in 11 patients (15.7%). All clinical findings had a high positive predictive value with poor sensitivity. In 11 patients (20%) chest X-rays were normal. Five foreign bodies (9.1%) were radiopaque. The most frequent radiological findings observed were localized air trapping (43.6%), followed by atelectasis (40%). The diagnostic sensitivity was 80% and the specificity 33% for the presence of a single positive radiological finding. CONCLUSIONS: Our study confirmed that clinical symptoms and radiological findings before bronchoscopy have a low diagnostic value in children with a history of FBA.

Adolescent↗
PubMedDate not supplied

[Sound lateralization regarding amplitude and time factors in various forms of hearing loss].

The ability to localize the sound source was investigated in 70 patients with hypoacusis of various type and degree, using interaural differences in time and intensity. The dichotic method of signal presentation was employed which made it possible to separately vary sound excitation of each ear. Isolated use of interaural differences in terms of time and amplitude was investigated by measuring lateralization thresholds, i.e. minimal interaural differences in time and intensity perceived as a displacement of the acoustic image from the head midline. It was found that lateralization of the acoustic image in response to interaural time and intensity differences followed different patterns. The precision of time lateralization depended on the level of hearing impairment and on binaural hearing asymmetry with respect to tone perception thresholds. The precision of intensity lateralization was dependent on the type of hypoacusis. The lowest thresholds of intensity lateralization were seen in patients with chronic adhesive otitis while the highest thresholds were detected in patients with 1st degree otosclerosis. It is recommended to use tests for measuring lateralization thresholds in terms of time and intensity in order to perform differential diagnostics of hearing impairment and functional prediction of hearing improvement interventions in otosclerosis and chronic otitis.

Auditory Perception↗
PubMed1988

Dynamic auditory localization: perceived position of a moving sound source.

Experiments are presented in which a sound source was moved at 15.2 cm/s over a horizontal path of 60 cm length, positioned at a 57 cm distance in front of the observer, symmetrically relative to the median plane. The subjects had to localize the sound at different moments of time. The sound source was predominantly mislocated in the direction of the movement; the mislocation increased at the end of the movement by up to 10-11 deg. In another condition the sound source was localized when it was stationary. In this case the mislocation was directed towards the median plane. The differences between the static and dynamic auditory localization are discussed.

Auditory Perception↗
PubMed1999

Improved auditory spatial acuity in visually deprived ferrets.

We have examined the effects on auditory spatial acuity in the horizontal plane of depriving ferrets of patterned visual cues by binocular eyelid suture in infancy or for a comparable period in adulthood. Minimum audible angles (MAAs) were measured for 500-, 100- and 40-ms broadband noise bursts at the midline and at 45 degrees to one side. A logistic regression analysis revealed no consistent difference between the midline MAAs of normal and infant lid-sutured ferrets. However, the lateral field MAAs of the infant-deprived group were significantly smaller and showed less inter-subject variability than those of normal-sighted ferrets. The animals deprived in adulthood were tested in the lateral field only, firstly 6 months after binocular eyelid suture and again after a further 10 months. For the first test, the MAAs achieved by these animals with 500- and 100-ms noise bursts were significantly smaller than the normal values and no different from those of the infant-deprived group. A significant improvement in performance at the two shortest stimulus durations (100 and 40 ms) was observed when the adult-deprived animals were re-tested. Their second-test MAAs did not differ from those of the infant-deprived group at any of the three stimulus durations used, and both groups achieved significantly better scores than the normal-sighted control animals. These results show that prolonged visual deprivation in both juvenile and adult ferrets can lead to a significant improvement in auditory spatial acuity in the lateral sound field. This is consistent with reports that congenitally blind humans can localize peripheral sounds more accurately than normal controls.

Acoustic Stimulation↗
PubMed2004

Representation of interaural temporal information from left and right auditory space in the human planum temporale and inferior parietal lobe.

The localization of low-frequency sounds mainly relies on the processing of microsecond temporal disparities between the ears, since low frequencies produce little or no interaural energy differences. The overall auditory cortical response to low-frequency sounds is largely symmetrical between the two hemispheres, even when the sounds are lateralized. However, the effects of unilateral lesions in the superior temporal cortex suggest that the spatial information mediated by lateralized sounds is distributed asymmetrically across the hemispheres. This paper describes a functional magnetic resonance imaging experiment, which shows that the interaural temporal processing of lateralized sounds produces an enhanced response in the contralateral planum temporale (PT). The response is stronger and extends further into adjacent regions of the inferior parietal lobe (IPL) when the sound is moving than when it is stationary. This suggests that the interaural temporal information mediated by lateralized sounds is projected along a posterior pathway comprising the PT and IPL of the respective contralateral hemisphere. The differential responses to moving sounds further revealed that the left hemisphere responded predominantly to sound movement within the right hemifield, whereas the right hemisphere responded to sound movement in both hemifields. This rightward asymmetry parallels the asymmetry associated with the allocation of visuo-spatial attention and may underlie unilateral auditory neglect phenomena.

Adult↗
PubMed2005

Perceptual categorization of sound spectral envelopes reflected in auditory-evoked N1m.

Magnetic responses to periodic complex sounds with equivalent acoustic parameters except for two different fundamental frequencies (F0) and 12 different spectral envelopes of vocal, instrumental, and linear shapes were recorded to determine the cortical representation of timbre categorization in humans. Responses at approximately 100 ms (N1m) to vocal and instrumental (nonlinear) sounds were localized significantly anterior to linear sound responses. N1m source strength for nonlinear sounds was significantly larger than that for linear sounds, and this difference was more marked in the left hemisphere than in the right. N1m peak latency only for vocal sounds was not affected by F0. Perceptual categorization was reflected in N1m source strength and location (linear or nonlinear), and in N1m latency (vocal or nonvocal).

Acoustic Stimulation↗
PubMed1997

The contribution of head motion cues to localization of low-pass noise.

Localization of low-pass sounds was tested in relation to aspects of Wallach's (1939, 1940) hypotheses about the role of head movement in front/back and elevation discrimination. With a 3-sec signal, free movement of the head offered only small advantage over a single rotation through 45 degrees for detecting elevation differences. Very slight rotation, as observed using a 0.5-sec signal, seemed sufficient to prevent front/back confusion. Cluster analysis showed that, in detecting elevation, some listeners benefited from rotation, some benefited from natural movement, and some from both. Evidence was found indicating that a moving auditory system generates information for the whereabouts of sounds, even when the movement does not result in the listener facing the source. Results offer significant if partial support for Wallach's hypotheses.

Female↗
PubMed2002

Manipulation of inhibition in the owl's nucleus laminaris and its effects on optic tectum neurons.

Differences in arrival time and intensity (or level) of sound between the ears serve as cues for localization of sound in many animals. Barn owls use interaural time difference (ITD) and interaural level difference (ILD) for localization in azimuth and elevation, respectively. The owl's brain processes these two cues in separate pathways. The nucleus laminaris is the first site that detects ITDs by methods of delay lines and coincidence detection. The nucleus ventralis lemnisci lateralis, pars posterior is the first site of processing ILDs. The two pathways merge in the inferior colliculus to give rise to sensitivity to combinations of ITD and ILD. This selectivity is relayed to the optic tectum where neurons are sensitive to both visual and auditory stimuli. The present paper reports the results of manipulating inhibition in the nucleus laminaris and its effects on the optic tectum neurons. Injection of GABA or muscimol (a GABA(A) receptor agonist) in the nucleus laminaris reduces the responses of its neurons to ITD. This finding proves that GABA(A) receptor-mediated inhibition acts on the nucleus laminaris neurons. The same treatment did not affect the neurons of the nucleus ventralis lemnisci lateralis, pars posterior, whereas it reduced the response of the optic tectum neurons to ITD-ILD pairs. We conclude that although the two pathways are independent, the process of combining ITD and ILD creates a new relationship in which the output of the neuron varies with the amplitude of either input. This conclusion is consistent with the recent finding that the combination sensitivity is due to a multiplication of ITD and ILD inputs.

Animals↗
PubMed2000

Cellular mechanisms for resolving phase ambiguity in the owl's inferior colliculus.

Both mammals and birds use the interaural time difference (ITD) for localization of sound in the horizontal plane. They may localize either real or phantom sound sources, when the signal consists of a narrow frequency band. This ambiguity does not occur with broadband signals. A plot of impulse rates or amplitude of excitatory postsynaptic potentials against ITDs (ITD curve) consists of peaks and troughs. In the external nucleus (ICX) of the owl's inferior colliculus, ITD curves show multiple peaks when the signal is narrow-band, such as tones. Of these peaks, one occurs at ITDi, which is independent of frequency, and others at ITDi +/- T, where T is the tonal period. The ITD curve of the same neuron shows a large peak (main peak) at ITDi and no or small peaks (side peaks) at ITDi +/- T, when the signal is broadband. ITD curves for postsynaptic potentials indicate that ICX neurons integrate the results of binaural cross-correlation in different frequency bands. However, the difference between the main and side peaks is small. ICX neurons further enhance this difference in the process of converting membrane potentials to impulse rates. Inhibition also appears to augment the difference between the main and side peaks.

Acoustic Stimulation↗