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PubMed1995

Involvement of cyclic AMP at the level of the nucleus reticularis pontis caudalis in the acoustic startle response.

Rats were implanted with cannulas in the nucleus reticularis pontis caudalis (PnC), an obligatory part of the neural pathway that mediates the acoustic startle reflex. Following at least 1 week of recovery, rats were tested for acoustic startle amplitude before or after infusion of compounds known to alter the second messenger, adenosine cyclic 3', 5'-monophosphate (cAMP). Local infusion into the PnC of the cAMP analog, 8-bromo cAMP (0.125-1.0 micrograms), increased the amplitude of the acoustic startle response in a dose-dependent manner. In addition, local infusion of a phosphodiesterase inhibitor, rolipram (10 micrograms) or the water soluble adenylate cyclase activator, forskolin-DHA (2.5 micrograms), produced a significant enhancement of startle amplitude. These effects probably resulted from intracellular actions because cAMP itself, which does not readily penetrate lipid membranes, had no effect. Moreover, the effects seemed somewhat specific because the precursor of cAMP, ATP or 8-bromo cGMP, also failed to alter startle at doses where 8 bromo-cAMP did. The fact that a phosphodiesterase inhibitor elevated startle suggests that cAMP serves to tonically elevate startle at this level of the pathway. Hence, treatments that either increase (fear, sensitization) or decrease (habituation, pre-pulse inhibition) startle at the level of the PnC may do so via release of neurotransmitters either positively or negatively coupled to cAMP, which in turn may alter either sound evoked transmitter release, excitability of PnC neurons or both.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1981

Strychnine: brainstem and spinal mediation of excitatory effects on acoustic startle.

The present study investigated the effects of the glycine antagonist strychnine on the acoustic startle response in rats. Strychnine (0.25, 0.50, 1.0, 1.25, 1.5 and 2.0 mg/kg) administered intraperitoneally (i.p.) was found to produce a dose-dependent increase in startle amplitude that reached its greatest magnitude within 10-15 min after injection. These doses did not produce convulsions or behavioral activation. In order to localize the site of action of this excitatory strychnine effect, rats were implanted with catheters in the lumbar region of the spinal cord (intrathecal implantation), in the cisterna magna, or in the lateral ventricle and later tested for startle after microinjections of strychnine. Dose-dependent excitatory effects on acoustic startle were found when strychnine was injected onto the spinal cord (3.12-12.5 microgram) or into the cisterna magna (6.25-25.0 microgram), whereas infusion into the lateral ventricle produced inhibition (6.25-25.0 microgram). The peak increases in startle following intrathecal (164%) and intracisternal (144%) strychnine were similar to the increase seen following systemic strychnine (160%). Thus, the excitatory effect of systemic strychnine appears to be mediated in the spinal cord and/or brainstem, consistent with data showing that glycine receptors are primarily localized in the caudal regions of the central nervous system. Furthermore, these results suggest that glycine exerts a tonic inhibitory influence on acoustic startle. The possible relation of such a system to phenomena that involve reduction in startle amplitude (e.g., habituation, pre-pulse inhibition) is discussed.

Acoustic Stimulation↗
PubMed1992

Changes in the acoustic nerve after hair cell regeneration.

Hair cells of the avian inner ear have been shown to regenerate following acoustic or ototoxic insult. The consequences of this regeneration on the acoustic nerve have yet to be defined. The purpose of the present study was to use TEM analysis following cochlear damage and hair cell regeneration to describe afferent and efferent neural terminals on hair cells in the newly repopulated sensory epithelium. Following acoustic overstimulation (12 h, 115 dB SPL, 1500 Hz) adult quail were sacrificed immediately (0 day), or at 2, 12, or 24 weeks. Serial thin sections were taken from the embedded papilla in a plane tangential to the basilar membrane in the area consistent with regenerative activity. Immediately following noise exposure very few hair cells could be seen within the epithelia; afferent terminals on remaining cells appeared normal. Two weeks later afferent terminals showed signs of degeneration; efferent terminals were rarely seen on tall hair cells but remained relatively normal on short hair cells. Three to six months later afferent terminals had regained a more normal appearance but were less numerous on tall hair cells; some return of efferent-like terminals was seen often contacting two tall hair cells. Large normal appearing, efferent terminals remained on short hair cells. These results suggest that regenerated hair cells are likely to receive neural innervation. It would appear that some degeneration of afferent terminals takes place prior to final innervation of new hair cells.

Acoustic Stimulation↗
PubMed1986

Analysis of the effect of using two different strain rates on the acoustic emission in bone.

To study the effect of strain rate on the acoustic emission amplitude signature of bone, bovine cortical bone was milled into standard tensile specimens which were tested at two different strain rates while being monitored with acoustic emission equipment. It was demonstrated that the amplitude distribution of the acoustic events in bone is dependent on strain rate. Greater numbers of events occurred with the slower strain rate (0.0001 s-1), but these events were of lower amplitude than those emitted during the more rapid strain rate (0.01 s-1). The plot of the cumulative event amplitude distribution followed the power-law model, and the slope of this output, the b-value, represented a signature of the amplitude distribution. The mechanical test results were consistent with the behavior of a viscoelastic multi-phase composite material.

Acoustics↗
PubMed1983

Some acoustic characteristics of oral reading by ten- to twelve-year-old children.

In contrast to the amount of information available on acoustic characteristics of adults' effective speech, little data are available on children's vocal effectiveness. A study, therefore, has been initiated to examine the relationship between some acoustic characteristics and listener judgments of children's vocal effectiveness. This paper reports the results of the first part of the study, that is, the acoustic analysis of oral reading by 36 10- to 12-yr-old children. The voice fundamental frequency characteristics, speaking time, pause time, and phonation-time ratio were measured using an automatic analysis method. Effects of the passage, repeated readings, and speaker sex are discussed.

Child↗
PubMed1986

Altered acoustic cue discrimination in Broca's and conduction aphasics.

The present investigation explored the acoustic cue discrimination abilities of eight Broca's and four conduction aphasic patients and nine normal controls. A word-discrimination test was used to assess the subjects' ability to discriminate selected acoustic cues for distinctive features of phonemes. The words differed from one another by a selected minimal feature, such as stop-gap duration, duration of fricative noise, direction and extent of final format transition, or relative location of friction noise in the spectrum. Results indicated that performance for normal and aphasic subjects was poorer for altered temporal subtest items than for altered spectral subtest items. Within the spectral subtest, fewer Broca's aphasics than conduction aphasics passed the items, while 90% of the normals passed. Within the temporal subtest, fewer conduction aphasics than Broca's aphasics passed the items, while 75% of the normal subjects passed this subtest. The results support previous research suggesting that deficiencies in auditory processing of selected acoustic cues are not limited to Wernicke's aphasic individuals but may be found to a varying degree in several aphasic groups.

Adult↗
PubMed1986

Clinical and acoustical variability in hypokinetic dysarthria.

Ten male patients with parkinsonism secondary to Parkinson's disease or progressive supranuclear palsy had clinical neurological, speech, and acoustical speech evaluations. In addition, seven of the patients were evaluated by x-ray computed tomography (CT) and (F-18)-fluorodeoxyglucose (FDG) positron emission tomography (PET). Extensive variability of speech features, both clinical and acoustical, were found and seemed to be independent of the severity of any parkinsonian sign, CT, or FDG PET. In addition, little relationship existed between the variability across each measured speech feature. What appeared to be important for the appearance of abnormal acoustic measures was the degree of overall severity of the dysarthria. These observations suggest that a better understanding of hypokinetic dysarthria may result from more extensive examination of the variability between patients. Emphasizing a specific feature such as rapid speaking rate in characterizing hypokinetic dysarthria focuses on a single and inconstant finding in a complex speech pattern.

Aged↗
PubMed1992

The use of artificial neural networks to estimate speech intelligibility from acoustic variables: a preliminary analysis.

Previous research has used regression analysis to attempt to predict the intelligibility of hearing-impaired speakers from acoustic speech parameters. Improvement of prediction may be achieved by the use of computerized artificial neural networks to process mathematically the acoustic input variables as part of the intelligibility process. A preliminary scheme for estimating speech intelligibility from acoustic parameters using a neural network is outlined and preliminary data illustrate its use.

Adult↗
PubMed1986

Cardiovascular concomitants of tactile and acoustic startle responses in spontaneously hypertensive and normotensive rats.

In the present study we have simultaneously investigated cardiovascular and behavioral responses to repeated tactile and acoustic stimulation in adult, male, spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Blood pressure and heart rate responses were increased in SHR vs. WKY rats following both types of stimuli. The pressor responses, but not the tachycardic responses, habituated with repeated stimulation in both strains and with both stimulus modalities. The rates of habituation were not significantly different between the two strains. Magnitudes of the behavioral startle responses were significantly elevated in SHR vs. WKY rats with tactile, but not with acoustic stimulation. No significant differences were found between the two strains with respect to the latency, with which the startle responses occurred. These data indicate that SHR as compared to WKY rats respond to repeated stimulation with two different stimulus modalities (tactile and acoustic) with significantly increased pressor and tachycardic responses. This cardiovascular hyperreactivity is not due to different degrees of habituation between the two strains and can be observed even in the absence of significant differences in standard behavioral startle response measures.

Acoustic Stimulation↗
PubMed1994

Modification of acoustic and tactile startle by single microwave pulses.

Single microwave pulses at 1.25 GHz were delivered to the head and neck of male Long-Evans rats as a prestimulus to acoustic and tactile startle. For acoustic startle, pulses averaging 0.96 microsecond in duration were tested with two specific absorption rate (specific absorption) ranges, 15.0-30.0 kW/kg (16.0-44.2 mJ/kg) and 35.5-86.0 kW/kg (66.6-141.8 mJ/kg), delivered 201, 101, 51, 3, and 1 ms before and 1 ms after onset of a startling noise. The low-intensity pulse did not affect peak amplitude, integral, or latency of the whole-body startle response. The high-intensity pulse at 101 and 51 ms inhibited the startle response by decreasing peak amplitude and integral; at 201 and 51 ms latency was increased. The high-intensity pulse at 1 ms enhanced the startle response by increasing peak amplitude and at 3 ms by increasing integral. For tactile startle, either microwave pulses averaging 7.82 microseconds in duration and 55.9-113.3 kW/kg (525.0-1055.7 mJ/kg) or 94 dB SPL clicks were delivered 157, 107, 57, and 7 ms before and 43 ms after onset of a startling air burst. The microwave pulse at 57 ms inhibited the startle response by decreasing peak amplitude; at 157, 107, 57, and 7 ms it increased latency. The microwave pulse at 43 ms after onset enhanced the startle response by increasing peak amplitude. The acoustic click at 157 and 57 ms inhibited the startle response by decreasing peak amplitude; at 157,2 107, and 57 ms it increased latency.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1981

Estrogen receptors in acoustic neurilemmomas.

Acoustic neurilemmomas are more frequent, larger, and more vascular in women, and such lesions have a rapidly progressive clinical course in pregnant women; these findings suggest that the growth of these neoplasms may bear a relationship to certain hormone levels. Tissues from 8 patients with acoustic neurilemmoma (3 men and 5 women) were studied by a new fluorescent steroid histochemical technique to detect the presence of estrogen receptors in or on neoplastic cells. Estrogen receptor protein has also been found in meningioma cells in women. Neurilemmoma of the acoustic nerve is the second neoplasm of the central nervous system in which such receptors have been demonstrated.

Adult↗
PubMed1986

Microsurgical anatomy of the brainstem surface facing an acoustic neuroma.

There is a consistent set of relationships on the brainstem surface facing an acoustic neuroma that provides the basis for identifying the displaced facial nerve on the medial side of the tumor. This review of the microsurgical anatomy of the brainstem surface facing an acoustic neuroma is based on the examination of the side of the brainstem during 42 operations for the removal of acoustic neuroma, and on the study of 50 cadaveric brains in the microsurgery laboratory. In the operative series, which included many large tumors, the facial nerve was preserved at operation in over 90% of the 42 patients. There was no mortality, and no need for cerebellar resection to remove the tumor in any patient.

Arteries↗
PubMed1994

The surgical management of benign intracranial meningiomas and acoustic neuromas in patients 70 years of age and older.

Over a 22-year-period (1967-1989) 80 patients 70 years of age and older underwent surgery for resection of a benign intracranial tumor. This group included 56 meningiomas and 24 acoustic neuromas. Forty-five of the tumors were completely excised, whereas 35 were partially removed. Tumor regrowth was documented in seven patients during the follow-up period, five of whom underwent additional surgery for resection of recurrent tumor. Thirty-six (64.3%) of the patients with meningiomas had only a minimal or no preoperative neurologic deficit, whereas twenty (35.7%) had a major deficit. Fifty-three (94.6%) patients who underwent surgery for resection of their meningioma made a good recovery (48 were improved or unchanged and five had minimal nonincapacitating worsening), one (1.8%) was worse, and two (3.6%) died. Fourteen (58.3%) of the patients with acoustic neuromas had only a minimal or no preoperative neurologic deficit, whereas 10 (41.7%) had a major deficit. Twenty-two (91.7%) of the patients who underwent surgery for resection of their acoustic neuroma made a good recovery (18 were improved or unchanged and four had minimal nonincapacitating worsening), two (8.3%) were worse, and none died. We conclude that, when indicated, surgery for intracranial meningiomas and schwannomas can be offered to patients 70 years of age and older with acceptable morbidity and mortality.

Aged↗
PubMed1994

Full recovery from deafness after removal of a large acoustic neurinoma associated with neurofibromatosis 2: case report.

The first case of full recovery from deafness after radical intracapsular removal of a large acoustic neurinoma, more than 4 cm in diameter, is reported. The patient, a 17-year-old woman, had multiple intracranial and intraspinal tumors in addition to bilateral acoustic neurinomas. Radical intracapsular removal is a useful technique to preserve nerves in patients with large acoustic neurinoma. When identifiable evoked potentials are preserved in brain stem auditory evoked potential, hearing preservation should be tried despite preoperative hearing level.

Adolescent↗
PubMed1983

Excitatory effects of the vasodilator hydralazine on acoustic startle in the rat.

Several drugs that functionally depress noradrenergic transmission depress acoustic startle amplitude (e.g., clonidine, phenoxybenzamine). Since these agents also depress blood pressure, the current study was designed to investigate the effects of hypotension per se (in the absence of decreased noradrenergic transmission) on the acoustic startle response. The vasodilator hydralazine was chosen because it produces marked hypotension in conscious rats, yet results in a compensatory increase in noradrenergic transmission (sympathetic rebound), rather than a decrease, as is seen with many other hypotensive agents. Hydralazine (0.3-20 mg/kg, IP) produced a marked and long-lasting increase in startle amplitude, compared to saline-treated controls. In a similar group of subjects, IP administration of 2.5 mg/kg hydralazine decreased mean arterial blood pressure by about 50% in conscious rats. Since, at the doses and treatment times employed in the present study, hydralazine decreases blood pressure but not startle amplitude, these data suggest that there is no relationship between changes in blood pressure and changes in startle amplitude across all drugs. Moreover, since hydralazine-induced hypotension results in an increase in noradrenergic transmission (sympathetic rebound), these data are consistent with the hypothesis that increases in central noradrenergic transmission increase acoustic startle amplitude. Lastly, since the most prominent direct action of hydralazine occurs in the periphery, hydralazine may alter startle through central actions that are triggered in the periphery.

Acoustic Stimulation↗
PubMed1990

Studies of respiratory stridor in young children: acoustical analyses and tests of a theoretical model.

Non-invasive procedures are proposed to aid the diagnosis of childhood laryngotracheal pathology and to monitor the course of such disease. The procedures capitalize on the one-to-one relationship which exists between the acoustic phenomena (stridors) associated with respiration and the configuration of the respiratory tract. Careful analysis of these acoustic patterns can thus assist in identifying and localizing constrictions, in diagnosis, and in monitoring disease severity. Based on the acoustical analysis of the stridor generated by children with congenital stridor, subglottal laryngitis, and trachea stenosis, the present paper demonstrates that a close relationship exists between the specific pathology and the spectrum of the associated respiratory stridor.

Acoustics↗
PubMed1993

The assessment of hypertrophy of nasopharyngeal tonsil by acoustical methods.

The possibilities for using acoustical analysis as a noninvasive measure of the degree of obstruction created by an enlarged pharyngeal tonsil (adenoid) are discussed. The method capitalizes on the relationship which exists between a specific obstruction of the respiratory tract and the resulting respiratory sound. Results indicate that as the adenoid increases in size relative to the size of the nasopharynx, the dominant components of the respiratory sound spectrum shift towards a higher frequency range. Furthermore, the correlation found between the assessments of the obstruction due to various sizes of the adenoid by radiological methods and acoustical analyses supports the theoretical prediction that information on the size of the constriction is carried by the respiratory sound. Therefore, careful analyses of the acoustic patterns in the respiratory sound can assist in identifying constrictions and monitoring the constriction changes in the upper respiratory tract.

Acoustics↗
PubMed1995

Acoustic features of normal-hearing pre-term infant cry.

Acoustic features of expiratory cry vocalizations were studied in 125 pre-term infants prior to being discharged from a level-3 neonatal intensive care unit. The purpose was to describe various phonatory behaviors in infants in whom significant hearing loss could be ruled out. We also compared these results with normal-hearing full-term infants, and evaluated whether linkage exists among acoustic cry features and various anthropometric, diagnostic and treatment variables obtained throughout the peri- and neonatal periods. Our analysis revealed that cry duration was significantly related to total days receiving respiratory assistance. The occurrence of other complex spectral and temporal aspects of acoustic cry vocalizations including harmonic doubling and vibrato also increased in infants receiving some form of respiratory assistance. The presence of harmonic doubling also depended on weight and conceptional age at test. The discussion focuses on the implication of these relationships and directions for future research.

Acoustics↗