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At least 1,207 records · Page 67Linked to original sources
PubMed1976

Role of neocortex in binaural hearing in the cat. II. The 'precedence effect' in sound localization.

The 'precedence effect' in sound localization refers to the situation in which two speakers, separated in space, emit identical sounds but one speaker leads by a few milliseconds. Normal observers perceive all the sound as originating from the leading speaker. In the present experiment cats were tested before and after unilateral ablation of auditory cortex on how well they could transfer a learned sound loclization response from situations involving unpaired sound sources to those with paired sources. Cats were tested with tone pairs separated by 5 msec and with clicks separated by delays of 3, 5, 7, 9, 12 and 16 msec. Preoperatively, the cats averaged 98% correct at a delay of 3 msec and 58% correct at 16 msec. Before surgery the probability of an error was independent of which speaker was leading; after surgery cats made significantly more errors when the leading speaker was located opposite the side of the lesion. Considerable individual variability was found with the 3 and 5 msec delay tests; some cats showed no evidence of a cortical deficit while others exhibited initial severe deficits which disappeared with training. At delays of 7-16 msec all cats showed severe directional deficits which were still present after 9 months of retraining. Results are interpreted as supporting the hypothesis that unilateral lesions disrupt binaural loudness rather than temporal relations.

Animals↗
PubMed1993

Evidence that corticotropin-releasing factor within the extended amygdala mediates the activation of tryptophan hydroxylase produced by sound stress in the rat.

Non-endocrine corticotropin-releasing factor (CRF) is believed to be involved in mediating stress behaviors in rats. The present study investigated the role of CRF in mediating the activation of tryptophan hydroxylase, the rate-limiting enzyme in serotonin synthesis, produced in response to sound stress. Bilateral injections of 0.5-3.0 micrograms of CRF directed towards the central nucleus of the amygdala increased tryptophan hydroxylase activity measured ex vivo when compared to vehicle-injected controls. This increase in enzyme activity, like that due to sound stress, was reversed in vitro by alkaline phosphatase. Intra-amygdala CRF (0.5 microgram) also enhanced the in vivo accumulation of 5-hydroxytryptophan (5-HTP) following the administration of m-hydroxylbenzylamine (NSD-1015, 200 mg/kg). The activation of tryptophan hydroxylase, produced by intra-amygdala CRF, was blocked by the CRF receptor antagonist alpha-helical CRF9-41 (10 micrograms). Additionally, the 5-HT1A agonist, gepirone, given either systemically (10 mg/kg) or intracerebrally into the region of the dorsal raphe (14 micrograms), blocked the tryptophan hydroxylase response to CRF. CRF did not increase tissue levels of 5-hydroxyindole acetic acid (5-HIAA) or the ratio of 5-HIAA to serotonin (5-HT) within the striatum of the same animals in which tryptophan hydroxylase activity was quantified, an effect produced by sound stress. Thus, while intra-amygdala CRF failed to mimic the sound stress response in its entirety, these data suggest that CRF is involved in mediating the activation of tryptophan hydroxylase produced by sound stress within the midbrain serotonin neurons.

Acoustic Stimulation↗
PubMed1995

Early, but not late, antiepileptic treatment reduces relapse of sound-induced seizures in the post-ischemic rat.

Global ischemia was used to induce a sensitivity to sound-triggered generalized seizures in 24 male Long-Evans rats. All showed a generalized seizure when exposed to a 108 dB bell for 1 min. They were assigned randomly to 3 groups of 8, and received 30 additional sound exposures. The early treatment group was injected with valproate (200 mg/kg i.p) 1 h prior to each of the first 10 sound exposures. The late treatment group received the same treatment during the second set of 10 sound exposures after 10 sound exposures without treatment. The third group was untreated. Both early and late treated groups had a significant reduction in seizure incidence during the treatment period, i.e. both groups showed seizure control. However, in the late group seizures returned promptly when valproate treatment was discontinued, while the early group showed a sustained reduction in seizure susceptibility. Since this outcome corresponds to seizure remission, the findings of this study favor early treatment.

Acoustic Stimulation↗
PubMed1994

Sound stress activation of tryptophan hydroxylase blocked by hypophysectomy and intracranial RU 38486.

The rapidly reversible increase in cortical or midbrain tryptophan hydroxylase activity observed ex vivo after exposure of rats to 1-h sound stress was blocked by hypophysectomy, but not sham hypophysectomy, and restored by dexamethasone administration to the hypophysectomized animals (500 micrograms/day i.p. for 3 days). The response to sound stress was also lost with deafferentation of the hypothalamus. These results indicate that hypothalamic control of adrenal glucocorticoids is required for the serotonergic response to sound stress. The glucocorticoid antagonist, RU 38486, given intracerebroventricularly (200 micrograms/day for 4-5 days) or bilaterally, into the region of the central nucleus of the amygdala (100 micrograms 15 min before stress), blocked the sound stress-induced increase in tryptophan hydroxylase activity. In contrast, the antimineralocorticoid, RU 26752, was without effect. The block obtained with RU 38486 suggests that glucocorticoid is required by the neurons that relay the effects of sound stress to the rostrally projecting serotonergic neurons.

Acoustic Stimulation↗
PubMed1988

B-mode ultrasound observations of bull testes during breeding soundness examinations.

The testes of 78 adult Beefmaster bulls (13 to > 31 mo old) were scanned with a 5 MHz, linear array portable ultrasound unit during routine breeding soundness examinations. Videotape recordings were used to measure mediastinum testis width and fluid width between visceral and parietal tunics (fluid width), and to count the number of fibrotic foci. Ultrasound results were compared to breeding soundness score parameters, which included total score, age classification, and percentage of primary and secondary sperm abnormalities. The overall mean mediastinum testis width and fluid width were 0.33 cm +/- 0.133 and 0.10 cm +/- 0.13, respectively; 15 testes had 1-8 fibrotic foci. There were no significant differences in mediastinum testis width and fluid width between left and right testes when compared by breeding soundness score classification or by age classification. There were no significant differences in mediastinum testis width, fluid width, breeding soundness score, or primary or secondary sperm abnormalities in bulls with fibrotic foci compared to bulls without fibrotic foci. There appears to be no significant information that routine testicular ultrasound examination adds to accepted breeding soundness evaluations performed on the same day.

Journal Article↗
PubMed1986

The lateralization of lip-read sounds: a first look.

Two tachistoscopic studies on the lateralization of lip-read still photographs in normal right handers are reported. In the first, subjects matched a still lip photograph with a heard speech sound. A clear right hemisphere (LVF) advantage emerged, despite the phonological requirements of this task. This pattern of laterality failed to interact with the type of response (same/different) or with the status of the heard phoneme; both consonant and vowel matching showed the same pattern of LVF advantage, despite the significantly greater difficulty of consonant than vowel matching in this particular task. In the second study subjects were required to speak the sound they saw being spoken by a centrally displayed face photograph. The displayed face was chimeric; that is, one side of the face was seen saying one sound, one side another. Here, a rather complex pattern of results ensued. For the speakers seen a clear expressor asymmetry emerged; speech sounds were judged more accurately when they issued from the right side of the speaker's face. However, in the LVF, and only the LFV, accuracy in reporting chimeric face sounds correlated with speed in learning to lip-read, suggesting that the LVF is systematically involved even when task demands (speaking the response, phonological analysis, small, more central displays) do not, at first sight, suggest that they should. Taken together, these studies suggest that the right hemisphere could support some aspects of the processing of seen speech in normally hearing, normally lateralized individuals.

Adolescent↗
PubMed1991

Formation of spike response to sound tones in cat auditory cortex neurons: interaction of excitatory and inhibitory effects.

Responses of the auditory cortical neurons to sound tones were studied extra- and intracellularly in anaesthetized cats. The pattern of response to tone stimuli could most differ in neurons tuned to the same sound frequency and forming a vertical cortical column. Phasic reactions were found in 69% of the neurons studied. Such neurons were encountered in all cortical layers but about 50% of them were localized at a depth of 0.4-1.0 mm, which corresponds to layers III and IV of the auditory cortex. Neurons with phasic reactions were able to respond to a relatively narrow frequency band that demonstrates high discriminative ability of these cells to the frequency analysis of sound signals. Inhibitory processes realized via both forward afferent and recurrent intracortical inhibition mechanisms play particular roles in the formation of phasic reaction of such neurons to different frequency tones. Twenty-six per cent of neurons generated tonic responses to the sound. The majority of such cells (94%) were localized at a depth of 1.0-2.2 mm, which corresponds to cortical layers V and VI. Inhibitory processes exert a much lesser influence on formation of tonic responses in comparison with phasic ones. Neurons of the tonic type, in contrast to phasic neurons, respond to a wider frequency band; their lower ability to discriminate sound frequency is obvious. Parameters of the responses of tonic neurons strictly correlated with the duration and intensity of the acoustic signal. The possibility of some tonic neurons playing an inhibitory role in auditory cortex is discussed [Volkov I. O. et al. (1989) Neurophysiology, Kiev 21, 498-506, 613-620 (in Russian)]. A small portion of the auditory area AI neurons (2%) demonstrated the suppression of background activity during tone stimulation. They were localized mainly in deep cortical layers (V and VI). Intracortical inhibition is supposed to play a dominant role in the formation of this type of response. About 3% of the studied auditory cortex neurons with background activity generated no response to tonic stimuli. Such cells were usually encountered in the superficial auditory cortex layers (I and II).

Acoustic Stimulation↗
PubMed1982

Interaction of aminooxyacetic acid and ethacrynic acid with intense sound at the level of the cochlea.

Results of previous investigation of the interaction of intense sound and drugs have, in general, failed to show a protective effect mediated by pre-administration with a drug having transient ototoxic effects. The present investigation was designed to further evaluate a protective effect found previously at the anatomical level and explained with an electrochemical theory of noise damage. The alternating current (a.c) potential and compound eighth nerve action potential (CAP) amplitude were monitored in aminooxyacetic acid (AOAA)- or ethacrynic acid (EA)-treated guinea pigs exposed to either moderate or high levels of intense sound and compared to changes observed in the same potentials in animals exposed to the intense sounds alone. Results showed protective effects only in the moderate--intense sound-exposure groups, with changes in sensitivity and voltage on the linear part of the input--output curve of the a.c cochlear potential found to be the only conditions where differences occurred. These results were difficult to interpret in terms of a protective effect and point to the need for obtaining additional data before an electrochemical mechanism is shown to play a role in the effect of intense sound on the cochlea.

Acetates↗
PubMed1985

Modulation at the guinea pig round window of summating potentials and compound action potentials by low-frequency sound.

Low-frequency sound was used to modulate responses to short single-frequency tone bursts at the guinea pig round window. Summating potentials (SP) increase (reach higher positive values) during the negative half-cycle of the low-frequency cochlear microphonic (LFCM) and decrease during the positive half-cycle of the LFCM. The compound action potential (AP) amplitude decreases during the negative half-cycle of the LFCM. The negative half-cycle of the LFCM can be identified with scala tympani displacement. SP modulation depth is defined as the difference between the highest and the lowest SP value found for tone burst stimulation at different phases of the low-frequency sound while the sound levels of the tone burst and the low-frequency bias are kept constant. When normalized with respect to the SP amplitude found without bias, the SP modulation depth is independent of the sound level of the tone burst in the range from 48 to 68 dB SPL. The normalized AP suppression tends to increase with decreasing tone burst sound level. A dynamic nonlinear mechanism which might explain these results is discussed. This mechanism is based on voltage-sensitive changes.

Acoustic Stimulation↗
PubMed1988

The active process is affected first by intense sound exposure.

Evidence exists to suggest that intense sound releases excess neurotransmitter from the inner hair cells. However, it has been previously reported that intense sound affects the cochlear micromechanics by altering the stereocilia. Therefore, we tested the hypothesis that intense sound affects structures involved in transduction before it affects the nerve endings. In order to test this hypothesis, we examined the interaction of intense sound with kynurenate which blocks the action of the neurotransmitter on the afferent nerve endings. Intracochlear perfusion of artificial perilymph containing 5 mM kynurenate did not reduce the effect of intense sound when we compare the results with a control group perfused with artificial perilymph alone. These results show that blockade of afferent transmitter receptors did not reduce the effect of acoustic trauma, and the acoustic trauma used herein affected structures involved in transduction before it affected the postsynaptic structures. We speculate that the active process is affected first during acoustic trauma. This interpretation is consistent with the notion that stereocilia are structures that make up part of the active process.

Action Potentials↗
PubMed1996

Intensity-dependent peak shift in cochlear transfer functions at the cellular level, its elimination by sound exposure, and its possible underlying mechanisms.

Our systematic study of cochlear transfer functions has confirmed earlier results that, in a normal cochlea, the cochlear AC responses at any given cochlear location do not have a fixed best frequency at which the response is maximal. The best frequency depends on sound intensity, shifting to lower frequencies as the intensity is increased. This phenomenon may account for the so called 'half-octave shift' of maximum cochlear damage relative to the frequency of the damaging sound observed in studies of auditory noise exposure. Our experimental results combined with the results of others and with our model studies bring us to the conclusion that, at low to moderate sound intensities, the dependence of the best frequency on sound intensity is due to an effect of the active feedback, which decreases as sound intensity increases. Consequently, the feedback, when present, must shift the best frequency upward.

Acoustic Stimulation↗
PubMed2005

Experimental ossicular fixations and the middle ear's response to sound: evidence for a flexible ossicular chain.

A human temporal-bone preparation was used to determine the effects of various degrees of artificial ossicular fixation on the sound-induced velocity at the input-side (the umbo of the malleus) and the output-side (the stapes) of the ossicular chain. Construction of various degrees of attachment between an ossicle and the surrounding temporal bone provided a range of reduction in ossicular mobility or "fixations". The results demonstrate different effects of the fixations on the umbo and stapes velocity: fixations of the stapes or incus produce larger reductions in sound-induced stapes velocity (as much as 40-50 dB with extensive stapes fixation), than reductions in umbo velocity (typically less than 10 dB). Fixations of the malleus produce similar-sized changes in both umbo and stapes velocity. These differential effects are consistent with significant flexibility in the ossicular joints (the incudo-malleolar joint and the incudo-stapedial joint) that permits relative motion between the coupled ossicles. The existence of flexibility in the ossicular joints indicates that joints in the ossicular chain can effect a loss of sound-induced mechanical energy between the umbo and the stapes, with a concomitant reduction in the sound-induced motion of the stapes. The introduction of such losses in sound transmission by the joints raises questions concerning the utility of three ossicles in the mammalian ear. The consequences of ossicular flexibility to ossicular-chain reconstruction is discussed. Also, as examined in a more clinically directed paper [Laryngoscope 115 (2005) 147], the different effects of the various ossicular fixations on the motion of the umbo and malleus may be useful in the diagnosis of the site of fixations in humans with conductive hearing losses caused by such pathologies.

Aged↗
PubMed2005

Functional organization of the forebrain auditory centres of the European starling: a study based on natural sounds.

The field L complex is thought to be the highest auditory centre and the input in the song vocal nuclei. Different anatomical and functional subdivisions have been described in field L. Auditory neurons of field L are well activated by natural sounds and especially by species-specific sounds. A complex sound coding appears to exist in field L. However, until now, the spatial organization of the different functional subdivisions has been described only using artificial sounds. Here, we investigated the spatial distribution of neuronal responses in field L to species-specific songs. Starlings seemed to be a very appropriate species for this investigation, both because of their complex vocal behaviour that implies different levels of categorization and their neuronal responses towards complex song elements. Multi-unit recordings were performed in wild starlings that were awake. The method of backward correlation was used to visualize the functional organization and we represented the neuronal responses as both activity maps and correlation maps. The use of natural sounds allowed us to define several functional sub-areas with different neuronal processing. These results show that field L is involved in a more complex task than simple frequency processing.

Acoustic Stimulation↗
PubMed2006

What's that sound? Matches with auditory long-term memory induce gamma activity in human EEG.

In recent years the cognitive functions of human gamma-band activity (30-100 Hz) advanced continuously into scientific focus. Not only bottom-up driven influences on 40 Hz activity have been observed, but also top-down processes seem to modulate responses in this frequency band. Among the various functions that have been related to gamma activity a pivotal role has been assigned to memory processes. Visual experiments suggested that gamma activity is involved in matching visual input to memory representations. Based on these findings we hypothesized that such memory related modulations of gamma activity exist in the auditory modality, as well. Thus, we chose environmental sounds for which subjects already had a long-term memory (LTM) representation and compared them to unknown, but physically similar sounds. 21 subjects had to classify sounds as 'recognized' or 'unrecognized', while EEG was recorded. Our data show significantly stronger activity in the induced gamma-band for recognized sounds in the time window between 300 and 500 ms after stimulus onset with a central topography. The results suggest that induced gamma-band activity reflects the matches between sounds and their representations in auditory LTM.

Acoustic Stimulation↗
PubMed2004

Auditory-visual temporal integration as a function of distance: no compensation for sound-transmission time in human perception.

In a psychophysical outdoor experiment with human subjects, the point of subjective simultaneity (PSS) of auditory and visual stimuli was measured for distances from 1 to 50 m. Repetitive sound and light pulses were presented with various stimulus-onset asynchronies, and subjects judged which modality came first. With increasing distance of the stimuli the PSS shifted in a linear relation toward delays of the light behind the sound. The slope of the regression line (3 ms/m) almost exactly corresponded to that of the temporal disparities resulting from the lower velocity of sound compared to light. These data refute the hypothesis proposed recently that there could be an 'implicit estimation' of sound-arrival time. The brain seems to eliminate such crossmodal temporal disparities by the integration of auditory and visual stimuli that fall into a time window, but not by specific compensatory processes that use an estimate of the sound delay.

Acoustic Stimulation↗
PubMed2004

Functional electrical stimulation of laryngeal adductor muscle restores mobility of vocal fold and improves voice sounds in cats with unilateral laryngeal paralysis.

Functional electrical stimulation (FES) has been proposed as a potential treatment for restoring motor functions of denervated motor systems. We investigated whether FES of paralyzed laryngeal adductor muscles could restore adduction to the vocal folds. In addition, we studied the effect of stimulated vocal fold adduction on the intensity and overall quality of voice production. We recorded movement of the vocal fold, electromyographic activity of muscles recruited for vocalization, and sound production in unanesthetized decerebrate cats during FES of the paralyzed thyroarytenoid (TA) muscle. FES of the paralyzed TA muscle induced adduction of the vocal fold. Appropriate stimulus parameters for induction was 1.5-3.0 mA intensity pulses delivered at a frequency of 30-50 pulses per second (pps). FES of the paralyzed TA muscle prolonged phonation time and increased intensity of voice sounds during vocalization induced by electrical stimulation (0.2 ms, 20-50 microA, 50 pps) of the periaqueductal gray (PAG). The quality of voice sounds evaluated by sound spectrography was shown to improve during vocalization with FES. We conclude that FES of the paralyzed laryngeal adductor muscle was effective in restoring adduction of the vocal fold and improving voice sounds impaired by unilateral laryngeal paralysis.

Animals↗
PubMed2004

Separate neural systems for processing action- or non-action-related sounds.

The finding of a multisensory representation of actions in a premotor area of the monkey brain suggests that similar multimodal action-matching mechanisms may also be present in humans. Based on the existence of an audiovisual mirror system, we investigated whether sounds referring to actions that can be performed by the perceiver underlie different processing in the human brain. We recorded multichannel ERPs in a visuoauditory version of the repetition suppression paradigm to study the time course and the locus of the semantic processing of action-related sounds. Results show that the left posterior superior temporal and premotor areas are selectively modulated by action-related sounds; in contrast, the temporal pole is bilaterally modulated by non-action-related sounds. The present data, which support the hypothesis of distinctive action sound processing, may contribute to recent theories about the evolution of human language from a mirror system precursor.

Acoustic Stimulation↗
PubMed2006

Investigation of spatial distribution of sound field parameters in ultrasound cleaning baths under the influence of cavitation.

Ultrasound cleaning baths fitting the full range from micromechanical components up to large machine parts, are regularly used in industry and in the lab. Despite the large number of applications, generally approved principles and objective criteria for parameter settings which allow an efficient operation are non-existent. The empirical selections of the running parameters often impede an optimization in terms of produce and reproducibility. One proposal for an objective description of the processes is the characterization of the sound field in the cleaning bath, which causes cavities, and subsequently, the cleaning process. Sound field measurements in the appropriate frequency range from 20kHz up to more then 1MHz incorporate a number of problems, such as large sensors disturbing the sound field, a lack of accuracy and the risk of being destroyed by cavitation bubbles. Measurement systems based on optical fiber tips and piezo-electrical hydrophones will be presented, which fulfil the accuracy requirements and withstand ultrasound fields with high power and cavitation. The spatial distribution of sound field parameters such as positive and negative peak pressure, amplitudes of fundamentals, harmonics and sub-harmonics as well as the energy density and spectral density in several frequency ranges are determined in experiments. Finally, the determined field parameters are related to the cavitation effects by means of photometric analysis of perforated aluminium foil. Perforations as well as intentions are analyzed and quantified from scanner images of the exposed foil samples using special image processing software. The experiments indicate clear differences in the structure of the sound fields and the spectral properties between the several types of cleaning baths, transducer arrangements and excitations.

Detergents↗