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PubMed2001

Effect of saliva substitutes on mineral content of demineralized and sound dental enamel.

The aim of this in vitro study was to evaluate the effects of commercially available saliva substitutes on the mineral content of pre-demineralized and sound enamel. From 56 bovine incisors 224 enamel specimens were prepared and hand-polished. The specimens were partially covered with nail varnish (control of sound enamel). In group 1, 112 samples were demineralized (18 days; 37 degrees C; pH 5.0) and a portion of the demineralized area was likewise covered with nail varnish. Subsequently, 16 specimens were exposed (14 days; 37 degrees C) to 10 ml of each of several different saliva substitutes (Artisial; Glandosane; Oralube; Saliva medac), or mouthwash solutions (Biotène; Meridol), respectively. Non-carbonated, fluoride-containing mineral water (Eptinger) was used as control. In group 2, the 112 sound enamel specimens were immersed directly in the solutions (without a demineralization period). After immersion, the specimens were cut perpendicular to the surface, and slabs (110 microns) were ground. Contact microradiographs were obtained and studied with a digital image-analyzing system. A dedicated software (TMR 1.24) was used to calculate the mineral content. Sound enamel (group 2) was significantly demineralized after immersion in Biotène and Glandosane (P < 0.001; Kruskal-Wallis). In group 1, mineral loss after storage in Biotène and Glandosane was significantly increased (P < 0.001), compared with the mineral content after demineralization. All other solutions revealed a significant mineral gain (P < 0.01; Wilcoxon), with the most pronounced effects after use of Oralube and mineral water (both containing calcium, phosphates, and fluorides). Therefore, administration of products similar to the last named can be recommended for dentate patients with salivary gland hypofunction.

Animals↗
PubMed2004

Spatial tuning curves along the chick basilar papilla in normal and sound-exposed ears.

Intense sound exposure destroys chick short hair cells and damages the tectorial membrane. Within a few days postexposure, signs of repair appear resulting in nearly complete structural recovery of the inner ear. Tectorial membrane repair, however, is incomplete, leaving a permanent defect on the sensory surface. The consequences of this defect on cochlear function, and particularly frequency analysis, are unclear. The present study organizes the sound-induced discharge activity of cochlear nerve units to describe the distribution of neural activity along the tonotopic axis of the basilar papilla. The distribution of this activity is compared in 12-day postexposed and age-matched control groups. Spontaneous activity, tuning curves, and rate-intensity functions were measured in each unit. Discharge activity at 60 frequency and intensity combinations was identified in the tuning curves of hundreds of units. Activity at each of these criterion frequency/intensity combinations was plotted against the unit's characteristic frequency to construct spatial tuning curves (STCs). The STCs depict tone-driven cochlear nerve activity along the length of the papilla. Tuning sharpness, low- and high- frequency slopes, and the maximum response were quantified for each STC. The sharpness of tuning increased with increasing criterion frequency. However, within a frequency, increasing sound intensity yielded more broadly tuned STCs. Also, the high-frequency slope was consistently steeper than the low-frequency slope. The STCs of exposed ears exhibited slightly less frequency selectivity than control ears across all frequencies and larger maximum responses for STCs with criterion frequencies spanning the tectorial membrane defect. When rate-intensity types were segregated, differences were observed in the STCs between saturating and sloping-up units. We propose that STC shape may be determined by global mechanical events, as well as localized tuning and nonlinear processes associated with individual hair cells. The results indicated that 12 days after intense sound exposure, global and local contributions to spatially distributed neural activity are restored.

Animals↗
PubMed2005

Effect of fMRI acoustic noise on non-auditory working memory task: comparison between continuous and pulsed sound emitting EPI.

Conventional blood oxygenation level-dependent (BOLD) based functional magnetic resonance imaging (fMRI) is accompanied by substantial acoustic gradient noise. This noise can influence the performance as well as neuronal activations. Conventional fMRI typically has a pulsed noise component, which is a particularly efficient auditory stimulus. We investigated whether the elimination of this pulsed noise component in a recent modification of continuous-sound fMRI modifies neuronal activations in a cognitively demanding non-auditory working memory task. Sixteen normal subjects performed a letter variant n-back task. Brain activity and psychomotor performance was examined during fMRI with continuous-sound fMRI and conventional fMRI. We found greater BOLD responses in bilateral medial frontal gyrus, left middle frontal gyrus, left middle temporal gyrus, left hippocampus, right superior frontal gyrus, right precuneus and right cingulate gyrus with continuous-sound compared to conventional fMRI. Conversely, BOLD responses were greater in bilateral cingulate gyrus, left middle and superior frontal gyrus and right lingual gyrus with conventional compared to continuous-sound fMRI. There were no differences in psychomotor performance between both scanning protocols. Although behavioral performance was not affected, acoustic gradient noise interferes with neuronal activations in non-auditory cognitive tasks and represents a putative systematic confound.

Acoustic Stimulation↗
PubMed2006

Development of a double-membrane sound generator for application in a voice-producing element for laryngectomized patients.

For voice rehabilitation after total laryngectomy a shunt valve is usually placed in the tracheo-esophageal (TE) wall, thereby enabling the production of a TE voice. Some patients, however, are unable to produce a voice of sufficient quality. Furthermore, the TE voice is low pitched, which presents a problem especially for female laryngectomized patients. The voice quality after laryngectomy might be improved by introducing a voice-producing element (VPE) into the TE shunt valve. In this study a sound generator was developed that is suitable for application in such a VPE. This sound generator consists of two elastic membranes placed parallel inside a circular housing. A substitute voice source is created when the membranes start to vibrate via a constant flow of air passing between them. To determine the optimal membrane configuration for proper functioning under physiological conditions, up-scaled physical VPE models with different membrane geometries were evaluated using in vitro experimental tests. For certain membrane geometries the tests showed that a basic sound, containing multiple harmonics, could be successfully produced under physiological air pressure and airflow conditions. The fundamental frequency (60-95 Hz) and sound pressure level (57-78 dB, at 15 cm microphone distance) were regulated via changes in the driving pressure, thereby enabling the possibility of intonation in laryngectomized patients' speech. The obtained frequency range is considered appropriate for producing a substitute voice source for female patients. The geometry considerations in this study can be used for the development of a true scale VPE that can be evaluated clinically, to eventually replace the voice after laryngectomy.

Female↗
PubMed1979

Postnatal effects of prenatal sound stimulation in the guinea pig.

Pregnant guinea pigs were stimulated with a natural sound alien to their species. Postnatally the response of their young to this sound was compared with that of unstimulated controls. All young were tested with a series of the alien sounds followed by series of guinea pig calls. Heart rate changes showed that prenatally stimulated young responded less to the alien sounds than did controls, whereas both groups responded equally to guinea pig calls. Response of controls diminished during daily test sessions and over the five test days and comparison with an older control group showed that this was due to repetition of the stimulus. It is suggested that the response of prenatally stimulated animals had waned before birth.

Animal Communication↗
PubMed1994

Acute and chronic effects of unilateral elimination of auditory nerve activity on susceptibility to temporary deafness induced by loud sound in the guinea pig.

The involvement of crossed cochlear pathways in modulating the deafening effects of loud sound was investigated in the anaesthetized guinea pig. Auditory nerve activity was blocked unilaterally, either by surgical cochlear destruction or intracochlear perfusion of lignocaine, and the effect of a standard loud sound exposure in the untreated ear was then assessed using the compound action potential (CAP) audiogram technique. It was found that both cochlear destruction or lignocaine perfusion reduced the amount of threshold elevation in the untreated ear. The effect of lignocaine perfusion was significantly greater than acute cochlear destruction. In animals allowed to survive for 24 h and one week post-cochlear destruction before loud sound exposure, the protective effect was still present and was significantly greater than immediately post-destruction. This long-term protective effect of contralateral cochlear destruction was blocked by administering strychnine prior to the loud sound exposure. The results of lignocaine perfusion and chronic destruction make it unlikely that protection immediately post-destruction is the result of a transient barrage of primary afferent activity. We conclude that elimination of auditory nerve input can alter the effectiveness of brainstem circuitry responsible for protection (possibly the olivocochlear system). Since acoustic stimulation of the contralateral ear also has acute protective effects thought to be mediated by olivocochlear efferents, the circuitry responsible for protection appears to be subject to a complex balance between excitatory and inhibitory influences.

Action Potentials↗
PubMed1995

Brain chimeras for the study of an avian model of genetic epilepsy: structures involved in sound and light-induced seizures.

The epileptic homozygotes of the Fayoumi strain of chickens (Fepi) are affected by photogenic reflex epilepsy with complete penetrance. Here we demonstrate that they are equally affected by audiogenic reflex epilepsy induced by intense sound stimulation. All the Fepi display sound-induced seizures from hatching to adulthood consisting of initial 'ictal arousal' and running fits usually followed by generalized clonico-tonic convulsions. A running fit is the preconvulsive motor symptom specifically induced by auditory stimulation while neck myoclonus is the preconvulsive motor symptom specifically induced by photic stimulation. The EEG interictal spikes and spike and waves are suppressed and replaced by a desynchronized trace during the seizures of both kinds. Viable neural chimeras were obtained by graft of embryonic brain vesicles from Fepi donors into normal chick embryos. Transfer of the complete audiogenic and photogenic phenotypes was obtained in chimeras resulting from embryonic substitution of both the prosencephalon and mesencephalon. The substitution of the prosencephalon alone resulted in transfer of interictal paroxysmal EEG activity accompanied by the sound and light-induced desynchronization and 'ictal arousal' with no motor seizures. Chimeras with embryonic substitution of the mesencephalon alone displayed running fits and convulsions induced by sound stimulation but only neck myoclonus following light stimulation. The conclusions are reached that: (i) the Fepi is a model of audiogenic and photogenic reflex epilepsy; (ii) in both types, the seizure initiator and the convulsion generator are localized in the brainstem, although reinforcement from telencephalic visual structures is needed to trigger photogenic generalized convulsions.

Acoustic Stimulation↗
PubMedDate not supplied

Stimulability considerations in the phonological treatment of a child with a persistent disorder of speech-sound production.

The term "persistent sound system disorder" has been used to describe the speech problems of a relatively small group of children that does not respond readily to treatment. This group includes children who have been given diagnoses such as development apraxia of speech. In this article, a rationale is developed for one approach to the treatment of persistent sound system disorder. This approach, which involves broadening of the phonetic inventory early in the treatment process, is contrasted with more traditional motor-programming treatments that emphasize stabilization of a restricted set of inconsistently produced sounds. The treatment procedures advocated in this article are illustrated in a case study. The article concludes with a discussion of evolving theories and technologies that are likely to impact upon the assessment and treatment of children with persistent sound system disorders in the future.

Articulation Disorders↗
PubMed1990

Overview of studies on liver carcinogenesis in English sole from Puget Sound; evidence for a xenobiotic chemical etiology. I: Pathology and epizootiology.

Livers of wild English sole (Parophrys vetulus) from polluted waterways and embayments of Puget Sound, Washington, are affected by a spectrum of multiple, co-occurring idiopathic hepatic lesions, including neoplasms, putative preneoplastic foci of cellular alteration, and unique degeneration conditions. Results from a statistical analysis of the patterns of co-occurrence of these lesions in wild English sole indicate that these lesions represent morphologically identifiable steps leading to the development of hepatic neoplasms. This sequence parallels the lesion progression in experimental models of chemically induced liver carcinogenesis in rodents. The hypothesis that these lesions in wild English sole can be caused by exposure to certain xenobiotic hepatotoxic and hepatocarcinogenic compounds in Puget Sound is based on: a) statistical associations between levels of aromatic hydrocarbons (sigma AHs) in sediment and prevalences of these idiopathic liver lesions, b) the contribution of sigma AHs in accounting for the variability in hepatic neoplasm prevalence in a logistic regression model, c) elevated odds ratios for several idiopathic hepatic lesion types in sole from polluted sites in Puget Sound, d) significant correlations between prevalences of idiopathic hepatic lesions and levels of fluorescent metabolites of aromatic compounds (FACs) in bile of English sole, and e) experimental induction of putatively preneoplastic focal lesions in English sole injected with a PAH-enriched fraction of an extract from a contaminated urban sediment from Puget Sound, that were morphologically identical to lesions found in wild English sole from the same site.

Animals↗
PubMed1986

A comparison of speech sound durations in three syndromes of aphasia.

This study compared the durations of selected vowels and consonants produced by three groups of aphasics and a normal control group in confrontation naming and single-word repetition tasks. There were seven aphasic subjects in each of the syndromes of Broca's, Wernicke's, amnesic, and conduction aphasia, in addition to a group of seven normal subjects. Wide-band spectrograms were used to measure speech sound durations. Analysis of group data revealed no significant differences in the durations of vowels or consonants across the four subject groups. In addition, there were no differences in speech sound durations for the confrontation naming versus repetition tasks. When two speech-language pathologists listened to tape recordings of all subjects performing the two tasks, they judged the speech of two Broca's aphasics as being labored, while the speech of the remaining subjects was not judged as labored. Clinical judgments of labored speech appeared to correspond to acoustical measurements of speech sound duration, as the two Broca's aphasics judged to be labored displayed longer durations than those subjects who were not judged as labored. The increase in duration was particularly marked for vowels and for sounds in polysyllabic words. The results are discussed in relation to current descriptions of the articulatory characteristics of Broca's aphasics. Clinical implications are also addressed.

Adult↗
PubMedDate not supplied

Complex sound analysis (frequency resolution, filtering and spectral integration) by single units of the inferior colliculus of the cat.

The central nucleus of the inferior colliculus (ICC) is a center of convergence of brainstem input and is critical for auditory information processing. Here, the analysis of complex sound spectra by single neurons in the ICC is investigated. Several measures of frequency resolution (excitatory/inhibitory tuning curves, effective bandwidths, critical ratio bands, critical bands derived using narrowband masking and two-tone separation paradigms) have been obtained from the responses of these neurons at sound pressure levels (SPL) up to 80 dB above the units' response thresholds (nearly 110 dB SPL). Among our results are the following: (1) Narrowband masking measures of critical bands from ICC neurons closely parallel behavioral measures using the same stimulus paradigm. (2) Frequency resolution power as measured by critical bandwidths varies little as a function of stimulus intensity. (3) Tuning curves of ICC neurons provide no simple basis for predicting the frequency filtering of the same neurons excited by complex sound spectra. (4) There is a frequency dependence of all measures of frequency resolution similar to that found in psychophysical determinations of critical bandwidths. That is, spatial frequency resolution in the cochlea is the origin for the resolution found in the ICC and in behavioral tests. (5) Lateral inhibition at the level of the ICC clearly plays a role in frequency resolution. (6) Frequency resolution is encoded by response rate changes of ICC neurons and is independent of tone response threshold, response latency, spontaneous activity, tone response type, binaural response type. It is concluded that spectral analysis of sound is established by processes, including lateral inhibition, independent of other basic response properties of neurons at the level of the ICC.

Acoustic Stimulation↗
PubMed1991

Regions in the B-mode image of a cylinder where the location of a point reflector is changed by sound speed variation.

The characteristics of the sonographic image representation of a point reflector caused by beam refraction when the reflector is placed behind a cylinder, are investigated. This cylinder acts on the ultrasonic beam as a lens, which explains the displacement in the observed reflector location(s). A mathematical model was constructed for a sonogram containing a cylindrical object with sound propagation speed different from its surroundings, and an experiment was designed to show the resulting inaccurate positions of the point reflector image. The image representation depends on the ratio of the sound speed in the cylinder to that of its surroundings. Depending on the location of the point reflector, additional artifacts are also observed. These artifacts occur in different regions (i.e., into two groups of regions for higher sound speed, and four groups of regions for lower sound speed in the cylinder).

Acoustics↗
PubMed1980

Mechanical and neural interactions between binaurally applied sounds in cat cochlear nerve fibers.

Most single fibers of the cochlear nerve (CN) in 22 cats exhibited effects of mechanical interaction in one cochlea between two sounds applied binaurally, similarly to results in two cats in which the contralateral CN was transected. In 11 of 189 fibers, the spontaneous and/or the sound-evoked activity was suppressed by a contralateral intense best-frequency sound; this indicates an interaural neural inhibition, probably through the olivocochlear bundle (OCB). The inhibited fiber population was small, and the intensity differences between the binaural sounds were exceptionally large, so that a simple negative feed-back function via the OCB is not likely.

Acoustic Stimulation↗
PubMed1995

Differential activation of the 5-hydroxytryptamine-containing neurons of the midbrain raphe of the rat in response to randomly presented inescapable sound.

Estimates of 5-hydroxytryptamine (5-HT) turnover in response to 30 min of inescapable, randomly presented, loud sound (sound stress) were obtained for regions of rat brain containing 5-HT perikarya by means of 5-hydroxytryptophan (5-HTP) accumulation after administration of an inhibitor of aromatic amino acid decarboxylase (100 mg/kg i.p., m-hydroxybenzylhydrazine, NSD 1015). Sound stress increased 5-HTP accumulation in the median raphe nucleus (MRN) twofold over that from sham-stressed controls, but did not change 5-HTP accumulation significantly in dorsal raphe nucleus (DRN) or hindbrain. These findings indicate that the 5-HT perikarya of the MRN but not those of the DRN or hindbrain are activated by sound stress, thus, provide further evidence for a functional distinction between the 5-HT neurons of these two midbrain nuclei.

5-Hydroxytryptophan↗
PubMed1988

An ipsilateral cochlear efferent loop protects the cochlea during intense sound exposure.

One suggested physiological function of the efferent nerve fibers innervating the cochlea is that they protect the cochlea against the effects of intense sound exposure. In order to test this hypothesis, we studied the effects of intense sound in the presence and in the absence of strychnine which blocks the efferent nerve fibers. The results show that in presence of strychnine an ipsilateral intense sound has a greater effect on the cochlea than in the absence of strychnine. We conclude that the ipsilateral cochlear efferents may act as protectors against intense sound exposure.

Action Potentials↗
PubMed1989

Effects of contralateral sound on auditory-nerve responses. I. Contributions of cochlear efferents.

The response properties of single auditory-nerve fibers in barbiturate-anaesthetized cats were recorded with and without simultaneous presentation of sound to the contralateral ear. The tendons to the middle ear muscles on both sides were cut before all experiments, and contralateral stimuli were restricted to levels below the threshold for crosstalk to the ipsilateral ear. Contralateral tones and broad-band noise were found to suppress the responses of auditory-nerve afferents to ipsilateral tones at their characteristic frequency (CF), but not to tones off CF. The suppression due to contralateral sound required approximately 100-200 ms to develop and to decay. When the contralateral stimuli were tones at the CF, the strongest suppression was observed in low- and medium-spontaneous-rate units with CFs between 1 and 2 kHz. The suppressive effect of contralateral sound completely disappeared immediately after severing the entire olivocochlear bundle (OCB) within the internal auditory meatus. the completeness of the OCB cuts was assessed histologically. Most of the suppressive effect remained after lesions to the OCB in the floor of the IVth ventricle which eliminated the crossed olivocochlear projection but spared most of the uncrossed projection. It is argued that this suppressive effect of contralateral sound is mediated by the uncrossed olivocochlear efferents to the outer hair cells.

Acoustic Stimulation↗
PubMed1992

The influence of loud sound on red blood cell velocity and blood vessel diameter in the cochlea.

Using intravital microscopy, we observed both decreases in red blood cell velocity and possible vasoconstriction in stria vascularis capillaries of the rat cochlea in response to loud sound (Quirk et al., 1991). However, our observation of vasoconstriction was subject to error in measurements from the two dimensional images obtained with our silicon intensified (SIT) camera due to the influence of focus causing image blur. The purpose of the current study was to apply an extended focus microscopy technique to obtain quantitative assessment of vessel diameter changes (Avinash et al., 1992), as well as to extend these studies to the guinea pig model. Broad-band sound stimulation at intensities of 84 dB SPL and 110 dB SPL were used. The results show that loud sound induces a sequence of changes in cochlear blood flow. Stimulation with 110 dB SPL resulted in a mean increase (maximum = 27%) in red blood cell velocity for the first 20 min of exposure followed by a gradual decrease below baseline (minimum = -12%) prior to termination of the signal. This velocity decrease and subsequent recovery were associated with significant changes in vessel diameters of selected and measured capillaries. In contrast, the 84 dB SPL stimulus caused an increase in red blood cell velocity (maximum = 20%) and vessel diameter (mean = 7.5) during the stimulation period. No recovery was observed during the 10 min observation period following sound. Several possible mechanisms responsible for these changes are discussed.

Acoustic Stimulation↗
PubMed1994

Spatiotemporal encoding of sound level: models for normal encoding and recruitment of loudness.

This study explores the hypothesis that sound level is encoded in the spatiotemporal response patterns of auditory nerve (AN) fibers. The temporal properties of AN fiber responses depend upon sound level due to nonlinearities in the auditory periphery. In particular, the compressive nonlinearity of the inner ear introduces systematic changes in the timing of the responses of AN fibers as a function of level. Changes in single fiber responses that depend upon both sound level and characteristic frequency (CF) result in systematic changes in the spatiotemporal response patterns across populations of AN fibers. This study investigates the changes in the spatiotemporal response patterns as a function of level using a computational model for responses of low-frequency AN fibers. A mechanism that could extract information encoded in this form is coincidence detection across AN fibers of different CFs. This study shows that this mechanism could play a role in encoding of sound level for simple and complex stimuli. The model demonstrates that this encoding scheme would be influenced by auditory pathology that affects the peripheral compressive nonlinearity in a way that is consistent with the phenomenon of recruitment of loudness, which often accompanies sensorineural hearing loss.

Acoustic Stimulation↗