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At least 1,279 records · Page 71Linked to original sources
PubMed2005

Contextual modulation of olivocochlear pathway effects on loud sound-induced cochlear hearing desensitization.

This study shows that the cochlear hearing losses [temporary threshold shifts (TTSs)] induced by traumatic sound and the effect of olivocochlear (OC) pathways to the cochlea on these hearing losses depend on the context of the sound. Background atraumatic white noise (WN) has been shown to 1) exacerbate loud-pure-tone-induced TTSs, and 2) promote the modulation of TTSs by the uncrossed OC (UOC) pathways additional to the action on TTSs, elicited by binaural loud tones themselves, by the crossed OC (COC) pathway. Here the same atraumatic WN reduced TTSs caused by loud narrow band sound. It also reduced TTS modulation by OC pathways. The UOC no longer exerted any effects on TTSs, and COC effects were significantly reduced in two discrete frequency bands: low frequencies within the narrow band ("within-band" frequencies) and high frequencies outside the band ("high-side" frequencies). COC effects were unchanged at high frequencies within the band. Despite these reductions in OC effects, because the WN itself reduced TTSs, the total effect of OC pathways and background WN now produced larger TTS reductions, especially at higher frequencies. Thus the modulatory effects of the OC pathways on TTSs depend on how background WN modulates cochlear state. It is postulated that the WN background and the OC pathways both modulate TTSs by acting on the outer hair cells, in a way that promotes the reduction of TTSs caused by the narrow band sound trauma. This joint promotion of a protective end-effect on TTSs to narrow band sound trauma contrasts against the effects seen with pure tone trauma where the same background WN exacerbated TTSs at high-side frequencies.

Acoustic Stimulation↗
PubMed2006

Distinct time scales in cortical discrimination of natural sounds in songbirds.

Understanding how single cortical neurons discriminate between sensory stimuli is fundamental to providing a link between cortical neural responses and perception. The discrimination of sensory stimuli by cortical neurons has been intensively investigated in the visual and somatosensory systems. However, relatively little is known about discrimination of sounds by auditory cortical neurons. Auditory cortex plays a particularly important role in the discrimination of complex sounds, e.g., vocal communication sounds. The rich dynamic structure of such complex sounds on multiple time scales motivates two questions regarding cortical discrimination. How does discrimination depend on the temporal resolution of the cortical response? How does discrimination accuracy evolve over time? Here we investigate these questions in field L, the analogue of primary auditory cortex in zebra finches, analyzing temporal resolution and temporal integration in the discrimination of conspecific songs (songs of the bird's own species) for both anesthetized and awake subjects. We demonstrate the existence of distinct time scales for temporal resolution and temporal integration and explain how they arise from cortical neural responses to complex dynamic sounds.

Animals↗
PubMed1978

Effect of auditory cortex ablation on localization and discrimination of brief sounds.

1. Dogs with bilateral auditory cortex lesions were tested on their ability to localize and discriminate brief sounds. In each test the animals were required to approach one of two goal boxes in order to indicate their response. 2. The results showed: a) that the operated animals could not solve the localization tasks when the goal boxes were located more than 125 cm away, but could solve the task if the goal boxes were located closer to the animal; b) that the operated animals could successfully discriminate brief bursts of click trains (i.e., 100/s versus 10/s, 0.3 s duration) even when required to indicate their discrimination by moving to goal boxes located 250 cm away, in spite of the fact that they could not successfully localize these sounds under similar conditions; c) that the operated animals tracked the source of a continuous sound instead of localizing it in a normal manner. 3. It appears that the deficit in sound localization resulting from cortical ablation is not due to any impairment in auditory attention or memory. Furthermore, the deficit cannot be ascribed to an inability to make a spatial response to an auditory cue. Instead, the deficit may be the result of a disconnection of the sound-localization mechanism from the motor mechanism necessary for some, though not all, behavioral responses.

Animals↗
PubMed1999

Long-term sound conditioning enhances cochlear sensitivity.

Sound conditioning, by chronic exposure to moderate-level sound, can protect the inner ear (reduce threshold shifts and hair cell damage) from subsequent high-level sound exposure. To investigate the mechanisms underlying this protective effect, the present study focuses on the physiological changes brought on by the conditioning exposure itself. In our guinea-pig model, 6-h daily conditioning exposure to an octave-band noise at 85 dB SPL reduces the permanent threshold shifts (PTSs) from a subsequent 4-h traumatic exposure to the same noise band at 109 dB SPL, as assessed by both compound action potentials (CAPs) and distortion product otoacoustic emissions (DPOAEs). The frequency region of maximum threshold protection is approximately one-half octave above the upper frequency cutoff of the exposure band. Protection is also evident in the magnitude of suprathreshold CAPs and DPOAEs, where effects are more robust and extend to higher frequencies than those evident at or near threshold. The conditioning exposure also enhanced cochlear sensitivity, when evaluated at the same postconditioning time at which the traumatic exposure would be delivered in a protection study. Response enhancements were seen in both threshold and suprathreshold CAPs and DPOAEs. The frequency dependence of the enhancement effects differed, however, by these two metrics. For CAPs, effects were maximum in the same frequency region as those most protected by the conditioning. For DPOAEs, enhancements were shifted to lower frequencies. The conditioning exposure also enhanced both ipsilaterally and contralaterally evoked olivocochlear (OC) reflex strength, as assessed using DPOAEs. The frequency and level dependence of the reflex enhancements were consistent with changes seen in sound-evoked discharge rates in OC fibers after conditioning. However, comparison with the frequency range and magnitude of conditioning-related protection suggests that the protection cannot be completely explained by amplification of the OC reflex and the known protective effects of OC feedback. Rather, the present results suggest that sound conditioning leads to changes in the physiology of the outer hair cells themselves, the peripheral targets of the OC reflex.

Acoustic Stimulation↗
PubMed2001

Feature analysis of natural sounds in the songbird auditory forebrain.

Although understanding the processing of natural sounds is an important goal in auditory neuroscience, relatively little is known about the neural coding of these sounds. Recently we demonstrated that the spectral temporal receptive field (STRF), a description of the stimulus-response function of auditory neurons, could be derived from responses to arbitrary ensembles of complex sounds including vocalizations. In this study, we use this method to investigate the auditory processing of natural sounds in the birdsong system. We obtain neural responses from several regions of the songbird auditory forebrain to a large ensemble of bird songs and use these data to calculate the STRFs, which are the best linear model of the spectral-temporal features of sound to which auditory neurons respond. We find that these neurons respond to a wide variety of features in songs ranging from simple tonal components to more complex spectral-temporal structures such as frequency sweeps and multi-peaked frequency stacks. We quantify spectral and temporal characteristics of these features by extracting several parameters from the STRFs. Moreover, we assess the linearity versus nonlinearity of encoding by quantifying the quality of the predictions of the neural responses to songs obtained using the STRFs. Our results reveal successively complex functional stages of song analysis by neurons in the auditory forebrain. When we map the properties of auditory forebrain neurons, as characterized by the STRF parameters, onto conventional anatomical subdivisions of the auditory forebrain, we find that although some properties are shared across different subregions, the distribution of several parameters is suggestive of hierarchical processing.

Animals↗
PubMed2002

Optical imaging of intrinsic signals in ferret auditory cortex: responses to narrowband sound stimuli.

This paper describes optical imaging of the auditory cortex in the anesthetized ferret, particularly addressing optimization of narrowband stimuli. The types of sound stimuli used were tone-pip trains and sinusoidal frequency and amplitude modulated (SFM and SAM) tones. By employing short illumination wavelengths (546 nm), we have successfully characterized the tonotopic arrangement, in agreement with the well-established electrophysiological tonotopic maps of the ferret auditory primary field (AI). The magnitude of the optical signal increased with sound level, was maximal for a modulation frequency (MF) of 2-4 Hz, and was larger for tone-pip trains and SFM sounds than for SAM sounds. Accordingly, an optimal narrowband stimulus was defined. Thus optical imaging can be used successfully to obtain frequency maps in auditory cortex by an appropriate choice of stimulus parameters. In addition, background noise consisting of 0.1-Hz oscillations could be reduced by introduction of blood pressure enhancing drugs. The optical maps were largely independent of 1) the type of narrowband stimulus, 2) the sound level, and 3) the MF. This stability of the optical maps was not predicted from the electrophysiological literature.

Acoustic Stimulation↗
PubMedDate not supplied

Crossed and uncrossed olivocochlear pathways exacerbate temporary shifts in hearing sensitivity after narrow band sound trauma in normal ears of animals with unilateral hearing impairment.

Olivocochlear (OC) pathways have been shown to reduce the temporary threshold shifts (TTSs) caused by traumatic sounds. More recently they have been shown to exacerbate TTSs under certain conditions. One condition is the normal-hearing ear of animals with a chronic unilateral hearing loss. Testing with pure tone trauma showed that then (a) the normal-hearing ear had a lower-than-normal 'intrinsic' susceptibility to intense tones, (b) binaural trauma exacerbated TTSs in the normal-hearing ear through the activity of uncrossed OC (UOC) pathways, and (c) there was no effect on TTSs of the crossed OC (COC) pathway to the normal-hearing ear. The present study is an examination in such animals of effects with noise band trauma. The effects here confirm the previous finding that under such conditions the normal-hearing ear has a lower-than-normal susceptibility to loud sound, and binaural loud sounds exacerbate TTSs in the normal-hearing ear. They extend the previous study by demonstrating that with this traumatic sound, both COC and UOC pathways exacerbate TTSs. These effects contrast against the effects seen in animals with bilaterally normal hearing for the same noise band. Given the commonality of unilateral hearing losses in the normal human population, these data have implications for the functional effects of the OC pathways on loud sound-induced hearing damage.

Animals↗
PubMedDate not supplied

HiResolution and conventional sound processing in the HiResolution bionic ear: using appropriate outcome measures to assess speech recognition ability.

OBJECTIVE: This study compared speech perception benefits in adults implanted with the HiResolution (HiRes) Bionic Ear who used both conventional and HiRes sound processing. A battery of speech tests was used to determine which formats were most appropriate for documenting the wide range of benefit experienced by cochlear-implant users. STUDY DESIGN: A repeated-measures design was used to assess postimplantation speech perception in adults who received the HiResolution Bionic Ear in a recent clinical trial. Patients were fit first with conventional strategies and assessed after 3 months of use. Patients were then switched to HiRes sound processing and assessed again after 3 months of use. To assess the immediate effect of HiRes sound processing on speech perception performance, consonant recognition testing was performed in a subset of patients after 3 days of HiRes use and compared with their 3-month performance with conventional processing. SETTING: Subjects were implanted and evaluated at 19 cochlear implant programs in the USA and Canada affiliated primarily with tertiary medical centers. PATIENTS: Patients were 51 postlinguistically deafened adults. MAIN OUTCOME MEASURES: Speech perception was assessed using CNC monosyllabic words, CID sentences and HINT sentences in quiet and noise. Consonant recognition testing was also administered to a subset of patients (n = 30) using the Iowa Consonant Test presented in quiet and noise. All patients completed a strategy preference questionnaire after 6 months of device use. RESULTS: Consonant identification in quiet and noise improved significantly after only 3 days of HiRes use. The mean improvement from conventional to HiRes processing was significant on all speech perception tests. The largest differences occurred for the HINT sentences in noise. Ninety-six percent of the patients preferred HiRes to conventional sound processing. Ceiling effects occurred for both sentence tests in quiet. CONCLUSIONS: Although most patients improved after switching to HiRes sound processing, the greatest differences were seen in the 'poor' performers because 'good' performers often reached ceiling performance, especially on tests in quiet. Future evaluations of cochlear-implant benefit should make use of more difficult measures, especially for 'good' users. Nonetheless, a range of difficulty must remain in test materials to document benefit in the entire population of implant recipients.

Adult↗
PubMed1991

Timing of the carotid arterial sounds in normal adult men: measurement of left ventricular ejection, pre-ejection period and pulse transmission time.

The first and second carotid arterial sounds (CaS1 and CaS2) were recorded simultaneously with the aortic valve echocardiogram, carotid pulse wave contour, heart sounds, and electrocardiogram in 27 healthy, normal subjects. The mean intervals between the onset of the QRS complex and the onsets of the first and second major components of the carotid arterial sounds were Q-CaS1 = 131 +/- 15 ms and Q-CaS2 = 412 +/- 36 ms, respectively. The mean delay of CaS1 after aortic valve opening was 43 +/- 6 ms, while the delay of CaS2 after aortic valve closure was 43 +/- 7 ms. The onset of CaS1 and CaS2 are exactly coincident with the upstroke and with the dicrotic notch of the carotid pulse wave contour. The recording of the carotid arterial sounds, heart sounds, and ECG has enabled us to measure systolic time intervals including the pre-ejection period, left ventricular ejection time, and pulse transmission time more easily than using the conventional method involving the carotid arterial pulse wave contour. The new approach provides accuracy and precision comparable to that of the previous methods.

Aortic Valve↗
PubMedDate not supplied

Mismatch negativity--the measure for central sound representation accuracy.

The mismatch negativity (MMN), elicited by any discriminable change in a repetitive sound even when this sound is not attended to, provides a pre-perceptual physiological measure of the accuracy of the central sound representation in the human brain. This accuracy, which can be measured separately for the different features of the sound, determines the individual's sound discrimination accuracy in normal and various pathological conditions.

Attention↗
PubMed1995

Effect of air-drying on demineralized and on sound coronal human dentine: a study on density and on lesion shrinkage.

Recently, several papers investigated the linear dimensional changes in dentine after air-drying. This paper pertains to weight changes, volume changes, and density changes caused by air-drying of sound and demineralized intact dentine. The densities of sound and artificially demineralized human coronal dentine were measured in the wet state and after various drying periods of up to 24 h. The volume was assessed either by means of a pyknometer (wet samples) or by means of dimension measurements. The air-drying experiments were done using a Mettler thermobalance at room temperature. The density of wet sound coronal dentine was found to be 2.24 +/- 0.12 g.cm-3; the value of wet demineralized dentine was about 1.6 g.cm-3. The data show that previously published density values of powdered sound dentine may have been influenced by powdering effects, air-drying, and air inclusion. In whole demineralized air-dried dentine, air inclusion can be very severe: up to 30% by volume. The results show furthermore that in demineralized dentine we have two drying stages: during the first one (up to about 10 min of air-drying), the lesions shrink about 23%, while a main part of the water in the lesion evaporates, and air is incorporated into the tissue; during the second stage (drying longer than 10 min), the lesions hardly shrink anymore, but water is evaporated mainly from underlying sound dentine, followed by air incorporation.

Air↗
PubMed1997

The effect of fluoridation on the occurrence of hidden caries in clinically sound occlusal surfaces.

It has been suggested that the diagnosis of occlusal dentine carious lesions has become more difficult due to the influence of fluoride on the character of pit and fissure surfaces. The issue pertains to the occurrence of hidden caries exemplified by occlusal surfaces judged as clinically sound but showing a radiolucency on the bite-wing radiograph. The aim of this study was to investigate the influence of water fluoridation on the occurrence of hidden caries in clinically sound occlusal surfaces in young people. The data of 515 persons (15 years of age) collected in 1968/1969 as part of the Dutch longitudinal epidemiological Tiel/Culemborg study were used. The participants in Tiel (F) were exposed to artificially fluoridated drinking water (F-concentration 1.1 ppm F) from birth until the end of the data collection. The participants in Culemborg (NF) were not exposed to extra fluoride (F-concentration 0.1 ppm F). In 1994 the status of occlusal surfaces of the first and second molars, as read from bite-wings made in 1968/1969, were judged by 2 investigators. (Cohen's Kappa intra- and inter-examiner agreement 0.90, 0.83 and 0.85, respectively). The original clinical data of 270 inhabitants of Tiel (F) and 245 of Culemborg (NF) were compared with the radiographic judgements. The children examined in Tiel (F) had a mean of 2.54 clinically sound occlusal surfaces in first and second molars (including surfaces with an enamel demineralization only) of which bite-wing radiographs detected 0.43 surfaces (16.9%) with a radiolucency into dentine. In Culemborg (NF) the children had a mean 0.65 clinically sound judged surfaces of which 0.16 (24.6%) showed a radiolucency on the bite-wing films. The results of the investigation show a proportional reduction of surfaces with hidden caries among clinically sound surfaces in the fluoridated area compared to the control.

Adolescent↗
PubMed1993

On perception of complex sound in schizophrenia and mania.

Eleven schizophrenic psychotic and 11 manic psychotic patients have been compared with each other and with a reference group of 34 dentists with respect to their emotional experience of seven complex nonverbal sounds. A rating form was used which measures three factors of emotional perception: tension-relaxation (factor I), gaiety-gloom (factor II), and attraction-repulsion (factor III). Analyses of variance of the factor scores revealed main tendencies between the psychopathological groups in factor I and III, i.e. schizophrenic psychotics rated the sounds generally as more tense and more attractive than manic psychotics. The manic psychotics rated the sounds as generally less tense and very much more attractive than the other groups. In factor II the manic psychotics rated one piece as significantly more gay than the other groups. It is discussed in what ways these differences of complex sound perception may be related to characteristic symptoms of the psychopathological states. No convincing evidence may be drawn from this study supporting the assumption that the two psychopathological groups might differ in a specific way in relation to any elementary structural property of the sounds.

Adolescent↗
PubMedDate not supplied

Response characteristics of cochlear nucleus neurons to vowel sounds.

Most studies in auditory neurophysiology have utilized tonal stimuli to determine the coding properties of neurons in the cochlear nuclei. In this investigation of the kangaroo rat, cochlear nuclei, neuronal responses to vowel sounds, as well as tones, were studied. The vowel sounds, each about 40 msec in duration were: see article. Five were linked together to form a 200 msec stimulus and various combinations of five vowel sounds provided us with 18 different stimuli. The results show that neurons in the cochlear nuclei are remarkably sensitive and selective to vowel sounds. Furthermore, the responses of these neurons to pure tones do not provide a complete basis to predict the types of responses to the vowel sounds. More significant is the finding that the neural discharge rate and pattern of discharge to a particular vowel may depend on where the vowel appears in the stimulus and what other vowel precedes it. This vowel positional effect is not the same for every neuron. We have called this phenomenon a neural "set".

Acoustic Stimulation↗
PubMed1996

Plaque pH and microflora of dental plaque on sound and carious root surfaces.

Given the hypothesis that root caries is the result of acid formation by acidogenic micro-organisms, the present study was performed to relate sucrose-induced pH response of dental plaque on root surfaces to the microbial composition of the overlying plaque. Seventeen caries-active elderly Chinese with poor oral hygiene and with both sound and carious root surfaces were examined. Plaque pH was measured before and up to one hour after a controlled sucrose mouthrinse. Plaque samples for microbiologic analyses were collected from 2 sound and 2 or 3 carious pH-measurement sites in each subject. The prevalence of the following micro-organisms was assessed as % of total viable counts on Brucella agar: Prevotella intermedia, Prevotella melaninogenica, Fusobacterium nucleatum, Campylobacter rectus, Capnocytophaga spp., Actinomyces viscosus, Actinomyces naeslundi, Streptococcus spp., S. sanguis, S. mitis, S. mutans, S. sobrinus, Lactobacillus spp., and Candida spp. There was no difference in plaque pH response on sound and carious root surfaces. The plaque pH response was more pronounced in the maxilla than in the mandible for both sound and carious sites. There was no difference in microbial composition of dental plaque on sound and carious root surfaces. The pH response to sucrose was the same regardless of the presence or absence of mutans streptococci. Our results thus do not readily support the traditional concept of caries formation.

Aged↗
PubMed1987

Clinical sound speed measurement in liver and spleen in vivo.

The paper describes an implementation of clinical sound speed measurement using either a commercial water path scanner or a specially developed dual transducer real time scanner, each interfaced to a general purpose minicomputer for off-line analysis. It describes the examination technique to obtain suitable in vivo clinical data from the liver and the spleen. It develops signal processing methods to achieve clinical confidence in individual measurements. Forty-five liver patients and 46 spleen patients were examined. Sound speed was found to correlate closely with fibrosis content in both the liver and the spleen with an increase in fibrosis resulting in a decrease in sound speed. Sound speed in various pathological conditions are discussed. Clinical results of sequential examinations on patients under treatment are presented and successful monitoring of the disease status is demonstrated. The potential clinical role of sound speed measurement is suggested.

Acoustics↗
PubMed2005

Optimal search strategies for detecting clinically sound prognostic studies in EMBASE: an analytic survey.

BACKGROUND: Clinical end users of EMBASE have a difficult time retrieving articles that are both scientifically sound and directly relevant to clinical practice. Search filters have been developed to assist end users in increasing the success of their searches. Many filters have been developed for the literature on therapy and reviews for use in MEDLINE, but little has been done for use in EMBASE with no filter development for studies of prognosis. The objective of this study was to determine how well various methodologic textwords, index terms, and their Boolean combinations retrieve methodologically sound literature on the prognosis of health disorders in EMBASE. METHODS: An analytic survey was conducted, comparing hand searches of 55 journals with retrievals from EMBASE for 4,843 candidate search terms and 8,919 combinations. All articles were rated using purpose and quality indicators, and clinically relevant prognostic articles were categorized as "pass" or "fail" according to explicit criteria for scientific merit. Candidate search strategies were run in EMBASE, the retrievals being compared with the hand search data. The sensitivity, specificity, precision, and accuracy of the search strategies were calculated. RESULTS: Of the 1,064 articles about prognosis, 148 (13.9%) met basic criteria for scientific merit. Combinations of search terms reached peak sensitivities of 98.7% with specificity at 50.6%. Compared with best single terms, best multiple terms increased sensitivity for sound studies by 12.2% (absolute increase), while decreasing specificity (absolute decrease 5.1%) when sensitivity was maximized. Combinations of search terms reached peak specificities of 93.4% with sensitivity at 50.7%. Compared with best single terms, best multiple terms increased specificity for sound studies by 7.1% (absolute increase), while decreasing sensitivity (absolute decrease 8.8%) when specificity was maximized. CONCLUSION: Empirically derived search strategies combining indexing terms and textwords can achieve high sensitivity or specificity for retrieving sound prognostic studies from EMBASE.

Abstracting and Indexing↗
PubMed1994

SOUND PRODUCTION AND HEARING IN THE PYRALID MOTH SYMMORACMA MINORALIS

Males of the moth Symmoracma minoralis (Snellen) (Lepidoptera: Pyralidae, Nymphulinae) were observed producing a high-intensity calling song (95 dB SPL at a distance of 10 cm) with a complex amplitude and frequency modulation (peaks of carrier frequency at 60 and 120 kHz). This sound is produced by a hitherto unknown type of sound organ located in the last abdominal (genital) segment, which may act as a tymbal. The observed directionality of sound output is probably achieved by means of a hollow cone surrounding the sound organ. Electrophysiological recordings revealed that the tympanal organs of S. minoralis are most sensitive in the frequency range from 50 to at least 100 kHz, which is distinctly higher than the minimum threshold levels in most other moths yet examined. The origin of genital sound production is discussed with respect to abdominal pheromone glands and pheromone-releasing movements.

Journal Article↗