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PubMed1993

Extralemniscal co-activation is not indispensable for behavioral detection of auditory stimuli.

Thresholds for triggering summed auditory evoked responses (ERs) were measured in non-auditory (= extralemniscal--EL) nuclei receiving direct auditory projections from the lateral lemniscus. Primary EL ERs with onset latency of 3-6 ms reflecting activation of direct EL projections of lemniscal auditory nuclei were registered in caudal pontine reticular nucleus (CPRN), in deep layers of superior colliculus (SC) and in ventromedial hypothalamus (VMH). Secondary EL ERs (waves of EL ERs with onset latency above 10 ms) reflecting diffuse auditory EL co-activation of the brain, were registered besides the above mentioned nuclei also in the medial amygdala (MA). Threshold sound intensities for evoking primary EL ERs in CPRN, SC and VMH, for secondary EL ERs in all extralemniscal nuclei tested, and for conditioned avoidance behavior in a two-way shuttle box, were compared mutually. There were no significant mutual differences among thresholds for inducing secondary EL ERs in all EL nuclei tested. Thresholds for evoking secondary EL ERs were lower than those for evoking primary EL ERs in deep layers of the SC, equaled to thresholds for primary EL ERs in the VMH and were higher than thresholds for primary EL ERs in the CPRN. The results suggest that auditory EL projections into SC and/or VMH (but not into CPRN) might represent the primary triggering source for secondary EL ERs in various extralemniscal nuclei. Although conditioning lowered the threshold intensities for inducing secondary EL ERs, the threshold sound intensity for triggering conditioned behavior was lower than the threshold for secondary EL ERs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Hearing threshold shift during auditory magnitude estimation.

The purpose of the present experiment was to determine the extent of hearing threshold shift that may occur during an auditory magnitude-estimation task involving stimulus intensities as great as 80 dB sensation level. Also, possible influences of hearing threshold shift on numerical magnitude-estimation responses and magnitude-function slopes were investigated. Results indicated that hearing threshold shift was insignificant (1-2 dB). Consistent small increases in numerical magnitude responses were observed on a magnitude-estimation task where hearing thresholds were retested between stimulus presentations versus a magnitude-estimation task where hearing thresholds were not retested. The stability of auditory magnitude functions across different conditions in the current investigation was in agreement with vibrotactile magnitude-scaling behavior observed by Fucci, et al. in 1989 and 1991. The over-all results supported the concept of an absolute, internal sensory-scaling mechanism being operable during magnitude estimation of auditory stimuli as discussed by Zwislocki and Goodman in 1980.

Adolescent↗
PubMed2004

Reception thresholds for sentences in bilingual (Spanish/English) and monolingual (English) listeners.

Recent evidence on the perceptual performance of bilingual listeners suggests that a nonaudibility-based cost exists in processing a second language. That is, when compared to monolingual English speakers and early bilinguals, listeners who acquired English as a second language after puberty show reduced performance when listening to the second language in background noise, despite normal auditory thresholds. However, past studies have not controlled for the homogeneity of the bilingual participants used in auditory research; therefore, it is unknown whether the deficit observed in bilingual function is due to a lack of control for language-related variables. The ability of a homogeneous group of Spanish-English bilinguals and English monolingual listeners to perceive sentences in quiet and in noise at threshold levels was evaluated using the Hearing in Noise Test (HINT). Both groups performed similarly in quiet conditions. In the noise conditions, the bilingual group's performance was significantly poorer than the monolingual group's performance. However, both groups showed a binaural advantage of 7-8 dB when the signal and noise were separated by 90 degrees.

Adult↗
PubMed1994

Rhythmic spontaneous activity in the developing avian auditory system.

Microelectrode recordings of spontaneous multiple unit activity were made from nucleus magnocellularis (NM) and nucleus laminaris (NL), second- and third-order nuclei in the chick auditory system, between 14 and 19 d of incubation (E14-E19). Spontaneous firing in E14-E18 embryos occurred in synchronous bursts at periodic intervals. A rhythmic pattern of spontaneous firing was also observed in the auditory nerve but not in nonauditory regions of the brain-stem. The mean interburst interval in NM and NL decreased from 4.9 sec at E14-E15 to 2.1 sec at E18. By E19, 2 d prior to hatching, synchronous bursting was replaced by an unpatterned, steady level of firing comparable to the background discharge that is present in NM and NL of hatchling birds. Bursting was not correlated with heart beat or respiration and was not affected by removal of the middle-ear ossicle. Rhythmic bursting could be reset, blocked, or induced by sound stimulation. Cochlea removal or pharmacological blockade of auditory nerve activity with TTX eliminated bursting. These results indicate that the synchrony and rhythmicity of impulse firing reflect normal physiological activity, most likely of cochlear origin. The present findings show that spontaneous activity in the embryonic avian auditory system, like that in the immature mammalian visual pathway (Maffei and Galli-Resta, 1990; Meister et al., 1991), occurs in a synchronously rhythmic pattern. This similarity raises the possibility that such activity may be a general feature of early sensory system development. Patterned spontaneous firing in the chick takes place during a period of embryogenesis when auditory thresholds are high and when it is unlikely that physiological function in ovo is influenced significantly by normally occurring levels of airborne sound. Brainstem auditory neurons undergo substantial changes in structure and innervation during this same period. It is speculated that the temporal pattern of spontaneous discharge may provide cues that contribute to these developmental events.

Acoustic Stimulation↗
PubMed2005

Cerebellar pilocytic astrocytoma with auditory presentation: case study.

An 8-year-old girl complained of decreased hearing and difficulty hearing from her right ear while on the telephone. Pure-tone and speech audiometry, immittance (tympanometry, acoustic reflex thresholds), auditory brainstem response, and transient click-evoked otoacoustic emissions were administered. The results were suggestive of a space-occupying lesion, and the patient was referred to a pediatric neurologist and neurosurgeon. A cerebellar pilocytic astrocytoma was found. The patient's audiologic profile is described, along with implications for pediatric neurologic evaluations.

Astrocytoma↗
PubMed2004

Noise-induced changes of neuronal spontaneous activity in mice inferior colliculus brain slices.

The inferior colliculus (IC) in vivo is reportedly subject to a noise-induced decrease of GABA-related inhibitory synaptic transmission accompanied by an amplitude increase of auditory evoked responses, a widening of tuning curves and a higher neuronal discharge rate at suprathreshold levels. However, other in vivo experiments which demonstrated constant neuronal auditory thresholds or unchanged spontaneous activity in the IC after noise exposure did not confirm those findings. Perhaps this can be the result of complex noise-induced interactions between different central auditory structures. It was, therefore, the aim of the present study to investigate the effects of noise exposure on the spontaneous electrical activity of single neurons in a slice preparation of the isolated mouse IC. Normal hearing mice were exposed to noise (10 kHz center frequency at 115 dB SPL for 3 h) at the age of 21 days under anesthesia (Ketamin/Rompun 10:1). After one week, auditory brainstem response (ABR) recordings and extracellular single-unit recordings from spontaneously active neurons within the IC slice were performed in noise-exposed and in normal hearing control mice. Noise-exposed animals showed a significant ABR threshold shift in the whole tested frequency range and a significant lower neuronal spontaneous activity in all investigated isofrequency laminae compared to controls. In both groups, the firing rate of 80% of IC neurons (approximately) increased significantly during the application of the GABA(A) receptor antagonist Bicucullin (10 microM). The present findings demonstrate a noise-related modulation of spontaneous activity in the IC, which possibly contribute to the generation of noise-induced tinnitus and hearing loss.

Acoustic Stimulation↗
PubMed2005

Erratum to "Noise-induced changes of neuronal spontaneous activity in mice inferior colliculus brain slices".

The inferior colliculus (IC) in vivo is reportedly subject to a noise-induced decrease of GABA-related inhibitory synaptic transmission accompanied by an amplitude increase of auditory evoked responses, a widening of tuning curves and a higher neuronal discharge rate at suprathreshold levels. However, other in vivo experiments which demonstrated constant neuronal auditory thresholds or unchanged spontaneous activity in the IC after noise exposure did not confirm those findings. Perhaps this can be the result of complex noise-induced interactions between different central auditory structures. It was, therefore, the aim of the present study to investigate the effects of noise exposure on the spontaneous electrical activity of single neurons in a slice preparation of the isolated mouse IC. Normal hearing mice were exposed to noise (10 kHz center frequency at 115 dB SPL for 3 h) at the age of 21 days under anesthesia (Ketamin/Rompun 10:1). After one week, auditory brainstem response (ABR) recordings and extracellular single-unit recordings from spontaneously active neurons within the IC slice were performed in noise-exposed and in normal hearing control mice. Noise-exposed animals showed a significant ABR threshold shift in the whole tested frequency range and a significant lower neuronal spontaneous activity in all investigated isofrequency laminae compared to controls. In both groups, the firing rate of 80% of IC neurons (approximately) increased significantly during the application of the GABA(A) receptor antagonist Bicucullin (10 microM). The present findings demonstrate a noise-related modulation of spontaneous activity in the IC, which possibly contribute to the generation of noise-induced tinnitus and hearing loss.

Acoustic Stimulation↗
PubMed2026

TECTB Variants Reveal Tectorial Membrane Vulnerability in Dominant Non-Syndromic Hearing Loss.

Identifying new genes responsible for non-syndromic hearing loss remains a critical goal as many patients still lack a molecular diagnosis despite comprehensive genetic testing. The tectorial membrane (TM) is a specialized acellular matrix of the inner ear, essential for stimulating mechanosensitive hair cell stereocilia bundles and maintaining frequency tuning and auditory sensitivity. Although mutations in genes encoding several non-collagenous proteins found in the TM (TECTA, CEACAM16, OTOG, OTOGL) have been identified as deafness genes, definitive evidence implicating β-tectorin (TECTB) has been lacking. Here, we present multiple lines of genetic and experimental evidence linking heterozygous missense variants in TECTB (NM_058222.3:c.674G>A, p.Cys225Tyr and NM_058222.3:c.853C>T, p.Arg285Cys), with hearing loss. Each variant affects highly conserved residues within or directly flanking the zona pellucida domain. Using a Tectb-C225Y knock-in mouse model, we show that homozygous animals exhibit severe hearing loss and profound disruption of TM morphology, while heterozygous animals display decreased staining density within the TM and increased susceptibility to noise-induced hearing loss, despite normal auditory thresholds. These findings identify TECTB as a novel human deafness gene, further elucidate its contribution to maintaining TM integrity and resilience against environmentally-related auditory decline.

beta‐tectorin (TECTB)↗
PubMed1995

Effects of developmental hypothyroidism on auditory and motor function in the rat.

Deafness is a common result of severe hypothyroidism during development in humans and laboratory animals; however, little is known regarding the sensitivity of the auditory system to more moderate changes in thyroid hormone homeostasis. The current investigation compared the relative sensitivity of auditory function, motor function, and growth to the effects of moderate to severe perinatal hypothyroidism in the rat. Rats received propylthiouracil (PTU) in drinking water at concentrations of 0, 1, 5, and 25 ppm from Gestation Day 18 until postnatal day (PND) 21, and the effects on their offspring were evaluated. At 1 ppm, PTU did not affect any of the measured endpoints. Serum thyroxin concentrations were sharply reduced in the 5 and 25 ppm PTU groups at all ages sampled (PND 1, 7, 14, and 21). Marked reductions in serum triiodothyronine (T3) concentrations were also detected for all ages > or = 7 at 25 ppm PTU, whereas no effects of 5 ppm PTU on serum T3 were apparent until PND 21. Compared to the controls, pups exposed to the highest dose of PTU demonstrated a delay in eye opening, reduced body weights, decreased and/or delayed preweaning motor activity, and persistent, postweaning hyperactivity. Only slight and transient effects on eye opening and ontogeny of motor activity were seen at the intermediate dose of PTU (5 ppm). Reflex modification audiometry revealed that, compared to controls, adult offspring from the 5 and 25 ppm treatment groups showed dose-dependent auditory threshold deficits (35 to > 50 dB) at all frequencies tested (1, 4, 16, 32, and 40 kHz). Such dose-dependent effects indicate that the developing auditory system may be sensitive to mild hypothyroidism, suggesting the possible need for routine audiometric screening for infants and children at risk for iodine deficiency, myxedema, and/or exposure to thyrotoxic environmental agents.

Acoustic Stimulation↗
PubMed1978

[High tone audiometry. II. Clinical application (author's transl)].

High tone audiometry, which is the testing of the auditory threshold between 8 and 16 KHz, increases the clinical usefulness of pure tone audiometry. Specific patterns of audiograph were obtained from 100 children and adults with auditory dysfunction of varied cause. The clinical application of high tone audiometry as an audiological aid to specific diagnosis should be pursued.

Adolescent↗
PubMed1997

Nonsurgical factors predictive of postoperative hearing for patients with vestibular schwannoma.

OBJECTIVE: The purposes of the study were to determine whether preoperative cochlear reserve as measured by evoked otoacoustic emissions (EOAE) as well as other hearing variables often associated with hearing preservation are correlated with hearing preservation after tumor removal and to determine whether any hearing variables are independent of tumor size as a predictor of hearing preservation. STUDY DESIGN: Preoperative audiologic data for 104 patients having vestibular nerve schwannomas removed via a retrosigmoid surgical approach were reviewed and subjected to factor analysis. SETTING: All patients were seen at the Mayo Clinic, Rochester, Minnesota. PATIENTS: The patient sample was divided into two groups based on hearing thresholds after surgery. Group I consisted of 73 ears without hearing preservation. The remaining 31 ears, group II, had preserved hearing (defined as average postoperative pure-tone thresholds < or = 85-dB HL for 0.5, 1, 2, and 3 kHz). MAIN OUTCOME MEASURES: Variables not predictive of hearing preservation were age, gender, tumor laterality, and cochlear reserve (EOAE). Variables predictive of hearing preservation were small tumor size, pure-tone hearing sensitivity, speech reception thresholds, word recognition scores, integrity of cochlear nerve (acoustic reflex thresholds, and auditory brain stem response [ABR] waveforms). RESULTS: A multivariate logistic regression analysis showed that only word recognition scores at 40-dB sensation level were independent of tumor size as a predictor of hearing preservation.

Acoustic Stimulation↗
PubMed2000

[Otoacoustic emissions, auditory evoked potentials, pure tone thresholds and speech intelligibility in cases of auditory neuropathy].

The combined findings of "normal evoked otoacoustic emissions (EOAE) and absent or markedly disturbed auditory evoked potentials from the brainstem and/or cortex" has been named auditory neuropathy in the English literature. The pure tone thresholds in these patients range from mild to severe loss. The loss of speech comprehension is out of proportion in comparison to the pure tone threshold elevation. This combination of findings suggests that cochlear function and in particular outer hair cell function, is normal in these patients but also suggests that the inner hair cell / VIII nerve functional unit is abnormal. Disruption in neural synchrony has previously been postulated as a reasonable explanation for the absent auditory brainstem response while otoacoustic emissions are preserved. Because the long-latency auditory evoked potentials, not having the stringent synchrony requirements of the ABR, may also be missing, the term synchrony - disruption may be somewhat misleading. The literature about auditory neuropathy is reviewed here: We now know that a set of salient features distinguishes these patients from the majority of patients with sensorineural hearing loss or other described syndromes. The symptoms defining auditory neuropathy are mild, moderate or severe elevation of auditory thresholds to pure tone stimuli by air and bone conduction, absent to severely abnormal ABRs to high level stimuli, present otoacoustic emissions (that do not suppress with contralateral noise), word recognition ability poorer than expected from the pure tone hearing loss configuration (in cases with mild to moderate hearing threshold elevation) and absent acoustic reflexes to both ipsilateral and contralateral tones. The entire set of findings, consistently seen in these patients, supports the importance of the crosscheck principle in diagnostic evaluation especially in children with delayed and/or impaired language acquisition. It is of ponderous importance that this disorder is not being confused with sensory hearing loss.

Adult↗
PubMed2003

Cisplatin ototoxicity in the guinea pig: vestibular and cochlear damage.

The aim of the present study was to investigate both vestibular and cochlear cisplatin toxicity. Twelve albino guinea pigs were divided into an experimental (n=8) and a control saline group (n=4) and were treated with cisplatin at a daily dose of 2.5 mg/kg for 6 consecutive days. Vestibular dysfunction was evaluated by computing the gain of the vestibular ocular reflex (VOR) evoked by stimulation in the horizontal (HVOR) and vertical (VVOR) planes. Changes in cochlear function were characterised as compound action potential threshold shifts. After the functional testing, tympanic bullae were removed and processed for morphological examination of the sensorineural epithelium. The onset of vestibular functional impairment was observed on the third day, although the VOR gain decrease was not significant. The impairment of the vestibular function progressed until the sixth day becoming statistically significant particularly at VVOR mid frequencies of stimulation. At these frequencies both macula and crista ampullaris functions are involved. Concomitantly a progressive auditory threshold shift was observed at all stimulus frequencies. The decline of the auditory function was statistically significant from the third day of treatment and it was more evident at high frequencies. Morphological observations showed a massive loss of outer hair cells and a degeneration of the organ of Corti in the basal/middle turns and only a slight loss of hair cells of the cristae ampullares and maculae. In conclusion, functional and morphological data provide evidence that the toxic effect of cisplatin is more pronounced in the organ of Corti than in the vestibular epithelium.

Action Potentials↗
PubMed1994

Auditory induction: reciprocal changes in alternating sounds.

When portions of a sound are replaced by a potential masker, the missing fragments may be perceptually restored, resulting in apparent continuity of the interrupted signal. This phenomenon has been examined extensively by using pulsation threshold, auditory induction, and phonemic restoration paradigms in which two sounds, the inducer and the inducee, are alternated (ABABA...), and the conditions required for apparent continuity of the lower amplitude inducee are determined. Previous studies have generally neglected to examine concomitant changes produced in the inducing sound. Results from the present experiments have demonstrated decreases in the loudness of inducers using inducer/inducee pairs consisting of tone/tone and noise/noise, as well as the noise/speech pairs associated with phonemic restorations. Interestingly, reductions in inducer loudness occurred even when the inducee was heard as discontinuous, and these decreases in loudness were accompanied by graded increases in apparent duration of the inducee, contrary to the conventional view of auditory induction as an all-or-none phenomenon. Under some conditions, the reduced loudness of the inducer was coupled with a marked alteration in its timbre. Especially profound changes in the inducer quality occurred when the alternating stimuli were tones having the same frequency and differing only in intensity--it seems that following subtraction of components corresponding to the inducee, an anomalous auditory residue remained that did not correspond to the representation of a tone.

Acoustic Stimulation↗
PubMed1990

Postnatal development of the middle ear: areal ratios in kittens.

Developmental changes in tympanic membrane to stapedial footplate areal ratios were investigated in kittens from birth through the twentieth postnatal day. Measurements from 45 kittens (85 temporal bones) were obtained from the pars tensa region of the tympanic membrane and the stapedial footplate region bounded by the annular ligament using standard macrophotographic and computer digitization techniques. Tympanic membrane and stapedial footplate areas were approximately 70% and 80%, respectively, of their adult size at birth and relevant areas increased exponentially during early postnatal life. Adultlike dimensions were achieved by the end of the first postnatal week. Tympanic membrane:stapedial footplate areal ratios increased from approximately 25:1 to 30:1 during the first postnatal week, before the developmental period during which adultlike auditory thresholds and response amplitudes are acquired. Thus, the areal ratio influences on impedance-matching characteristics of the middle ear do not appear to significantly affect the postnatal development of auditory function in cats.

Animals↗
PubMed1983

[Acoustic stimulation and adaptation to noise of the developing mouse auditory system].

To assess the effects of an acoustically enriched environment during the auditory system development, groups of mouse pups, from two strains (Swiss Albinos Rb-3 and deafness, the latter carrying a recessive gene [dn] making homozygous dn/dn totally deaf), were exposed to pulsed pure-tone stimulation (2 500 Hz; 85 +/- 5 dB SPL) at different periods of development from conception to weaning. Growth curve, weight at 40 days, eye opening and behaviour at 24 days to the same stimulus were analyzed as a function of the mother's audition (hearing or deaf) and of the period of acoustic exposure: exposed since conception, since birth or from 9 days (date of onset of audition). Eye opening is more precocious in all three experimental groups than in controls. Contrary to mouse pups exposed from 9 days, those (also from deaf mothers) treated before onset of hearing show normal growth and behavioural indifference to the stimulus at 24 days. The significant lack of physiological and behavioural effect of the sound stimulus in the groups treated before electrophysiological maturation of hearing has a certain lasting effect, at least up to age 40 days. As electrophysiological studies show no alteration of auditory thresholds in these groups, the hypothesis of a possible process of habituation, stemming from a very early effect of sound stimulation during the non-functional phase of development of the auditory system (from birth to 9 days), is discussed.

Acoustic Stimulation↗