Neurometamorphosis of the ear in the gypsy moth, Lymantria dispar, and its homologue in the earless forest tent caterpillar moth, Malacosoma disstria

The adult gypsy moth, Lymantria dispar (Lymantriidae: Noctuoidea) has a pair of metathoracic tympanic ears that each contain a two-celled auditory chordotonal organ (CO). The earless forest tent caterpillar moth, Malacosoma disstria (Lasiocampidae: Bombycoidea), has a homologous pair of three-celled, nonauditory hindwing COs in their place. The purpose of our study was to determine whether the adult CO in both species arises from a preexisting larval organ or if it develops as a novel structure during metamorphosis. We describe the larval metathoracic nervous system of L. dispar and M. disstria, and identify a three-celled chordotonal organ in the anatomically homologous site as the adult CO. If the larval CO is severed from the homologue of the adult auditory nerve (IIIN1b1) in L. dispar prior to metamorphosis, the adult develops an ear lacking an auditory organ. Axonal backfills of the larval IIIN1b1 nerve in both species reveal three chordotonal sensory neurons and one nonchordotonal multipolar cell. The axons of these cells project into tracts of the central nervous system putatively homologous with those of the auditory pathway in adult L. dispar. Following metamorphosis, M. disstria moths retain all four cells (three CO and one multipolar) while L. dispar adults possess two cells that service the auditory CO and one nonauditory, multipolar cell. We conclude that the larval IIIN1b1 CO is the precursor of both the auditory organ in L. dispar and the putative proprioceptor CO in M. disstria and represents the premetamorphic condition of these insects. The implications of our results in understanding the evolution of the ear in the Lepidoptera and insects in general are discussed.     

Aplasia and hypoplasia of the vestibulocochlear nerve: diagnosis with MR imaging

PURPOSE: To introduce aplasia or hypoplasia of the vestibulocochlear nerve (VCN) as a possible cause of hearing loss and to identify the magnetic resonance (MR) imaging characteristics of this entity. MATERIALS AND METHODS: In seven patients with congenital deafness or unexplained sensorineural hearing loss, MR imaging enabled diagnosis of aplasia or hypoplasia of the VCN. Axial (0.7-mm) three-dimensional Fourier transformation-constructive interference in steady state (3DFT-CISS) images and parasagittal reconstruction images perpendicular on the course of the VCN were obtained. Twenty normal inner ears were also studied; their findings were compared with those of the patients. RESULTS: The facial nerve and inferior and superior vestibular and cochlear branches of the VCN were identified on the MR images in the 20 normal inner ears. Aplasia of the VCN was detected in two patients with normal labyrinths but with a severe stenosis of the internal auditory canal. A common VCN with absence of the cochlear branch was found bilaterally in two patients with a congenital malformation of the labyrinth. A common VCN with absence or hypoplasia of the cochlear branch was found in three patients with normal internal auditory canals and labyrinths. CONCLUSION: Submillimetric gradient-echo images (eg, 3DFT-CISS) should always be used to exclude aplasia or hypoplasia of the cochlear branch of the VCN in all cochlear implant candidates and patients with congenital deafness. This entity, which can occur with or without associated labyrinthine malformation, should be confirmed in two planes.     

Temporal patterns of transient-evoked otoacoustic emissions in normal and impaired cochleae

The spatial distribution of outer hair cells that participate in generating transient-EOE frequency-components has been investigated in man. According to several models (e.g. Wilson (1990) Hear. Res. 2, 527-532; Zwicker (1986) J. Acoust. Soc. Am. 80, 154-162; Wilson and Kemp (Eds.), Cochlear Mechanisms, Structures, Functions and Models, Plenum Press, NY), EOEs result from interferences between broadly distributed contributions, responsible for their long frequency-dependent delay. This work presents an analysis of the temporal patterns of click- and tone-burst-EOEs in human ears when contributions to EOEs are reduced by noise-induced lesions with audiometric notches centred around 4 kHz (N = 46). Although the auditory thresholds at the frequencies of the studied EOE-components were always normal, these components exhibited drastic and predictable changes compared to normal control ears (N = 40). (1) Their temporal pattern at the highest EOE frequency fmax just below the audiometric notch appeared to be determined by the cochlear state at high frequencies (6 to 8 kHz). Either it was normal and the EOE exhibited a complicated beat-structure, or it was impaired and the time envelope of the EOE was simple. In contrast, any type of time pattern could be observed in normal ears. (2) The temporal patterns of EOEs one octave below fmax always presented many beats and short delays. The proposed interpretation is that contributions to a transient-EOE component at frequency f can come from distant basal cochlear areas, i.e. more than 1 and sometimes 1.5 octaves from the place tuned to f. Therefore, the possible relationships between transient-EOEs and tuning mechanisms which presumably involve only a small number of OHC need further investigations.     

Cytochemical and biochemical studies on adenylate cyclase activity in preneoplastic and neoplastic liver tissue and cultured liver cells

OBJECTIVE: To assess the accuracy of: 1) distortion product otoacoustic emission (DPOAE) measures for the identification of frequencies at which auditory sensitivity is normal or near normal; and 2) click and nonmasked tone burst-evoked auditory brain stem response (ABR) thresholds for behavioral threshold estimation for children with sensorineural hearing loss characterized by islands of normal sensitivity. DESIGN: DPOAEs and ABRs were recorded from five hearing-impaired and eight normal-hearing pediatric ears. The accuracy with which DPOAEs permitted identification of frequencies at which elevated hearing thresholds were present was examined. ABR and pure-tone threshold differences for the impaired ears were calculated. RESULTS: For three of the five hearing-impaired ears, significant impairments would have been missed based on click-evoked ABR thresholds. One of those hearing-impaired ears provided an essentially normal 500 Hz tone burst-evoked ABR threshold as well. Four of the hearing-impaired ears provided a 500 Hz tone burst-evoked ABR threshold within 10 dB of the respective pure-tone threshold. However, click-evoked ABR and 500 Hz tone burst-evoked ABR threshold data did not adequately delineate the hearing loss configuration for hearing aid frequency response selection. DPOAEs were present at three out of four frequencies from 1000 to 4000 Hz at which sensitivity was normal or near normal (< or =25 dB HL) and absent at 10 out of 11 frequencies at which sensitivity was impaired. The use of DPOAEs to identify frequencies at which sensitivity was normal and the use of tone burst ABR thresholds at frequencies where DPOAEs were absent provided a better estimate of these pure-tone audiograms than was provided by click-evoked and 500 Hz tone burst-evoked ABR thresholds.     

Magnesium isotopic abundance measurement in humans: comparison of two mass spectrometric methods

OBJECTIVE: A population of children having bilateral moderate to profound hearing impairment was investigated to find out the number who passed (false negatives) and who failed (true positives) a screening test based on the auditory brain stem response (ABR). DESIGN: This study of the ABR is a parallel report to Lutman, Davis, Fortnum, and Wood (1997), where the transient evoked otoacoustic emission was examined on a similar but not identical population of at-risk neonates. Hearing screening was undertaken in at-risk neonates (targeted screening) at seven hospitals in the UK using the Nottingham ABR Screener. During the period from January 1988 to December 1993, a total of 6983 neonates had been tested. Assessment of audiological records from the participating centers ascertained that 201 children born between January 1988 and December 1993 had hearing threshold levels in both ears of 50 dB or more, averaged over the speech frequencies 0.5, 1, 2, and 4 kHz. Of these, 51 had completed the ABR screening test. Examination of the ABR records, which included both machine and visual scoring, indicated whether they had passed or failed the screening test. RESULTS: Forty-six of the 51 hearing impaired babies failed the neonatal ABR screen either on one or both ears (five false negatives), and 42 failed the test on both ears (nine false negatives). This resulted in field sensitivities of 90% and 82%, respectively. Two cases of suspected progressive hearing loss have been included in the numbers of false negative results. The percentage of babies passing the screen on both ears and subsequently having normal hearing (specificity) is typically 93%. CONCLUSIONS: Neonatal hearing screening in an at-risk population using a highly automated ABR test is a viable and effective tool for identification of hearing impairment. Although the field sensitivity of the test is high, it is unable to identify all babies with a criterion level of hearing loss. There are a number of possible explanations as to the origin of false negative results: configuration of the pure-tone audiogram, a progressive hearing loss, acquired sensorineural or conductive loss, retrocochlear deafness, or an incorrect interpretation of the screening test. Passing a neonatal screening test, therefore, does not exclude the possibility of subsequent hearing impairment and highlights the need for further surveillance.     

Recruitment deafness: Functional effect of priming-induced audiogenic seizures in mice.

Investigated the absolute threshold of the auditory evoked potential (AEP) at the level of the inferior colliculus in 30 C57BL/6J mice. In Exp I, acoustic priming at 16 days of age, which induces susceptibility to audiogenic seizures, elevated this threshold for individual frequencies from 5 kHz to 25 kHz in 21-day-old mice by 5-11 db. In Exp II, the amplitude of the AEP was examined in response to a flat 10-20 kHz noise band. At low intensities, the AEP amplitude was considerably higher for nonprimed Ss, but at high sound levels this relationship reversed. Results indicate that primed mice show recruitment deafness and offer a method of investigating recruitment deafness in humans. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Change deafness and the organizational properties of sounds.

Change blindness, or the failure to detect (often large) changes to visual scenes, has been demonstrated in a variety of different situations. Failures to detect auditory changes are far less studied, and thus little is known about the nature of change deafness. Five experiments were conducted to explore the processes involved in change deafness by measuring explicit change detection as well as auditory object encoding. The experiments revealed that considerable change deafness occurs, even though auditory objects are encoded quite well. Familiarity with the objects did not affect detection or recognition performance. Whereas spatial location was not an effective cue, fundamental frequency and the periodicity/aperiodicity of the sounds provided important cues for the change-detection task. Implications for the mechanisms responsible for change deafness and auditory sound organization are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transient evoked otoacoustic emissions in patients with normal hearing and in patients with hearing loss

OBJECTIVES: 1) To evaluate transient evoked otoacoustic emission (TEOAE) test performance when measurements are made under routine clinical conditions. 2) To evaluate TEOAE test performance as a function of frequency and as a function of the magnitude of hearing loss. 3) To compare test performance using univariate and multivariate approaches to data analyses. 4) To provide a means of interpreting clinical TEOAE measurements. DESIGN: TEOAEs were measured in 452 ears of 246 patients. All measurements were made after acoustic immittance assessments, which were used to demonstrate that middle-ear function was normal at the time of the TEOAE test. TEOAE amplitudes and signal to noise ratios (SNRs), analyzed into octave bands centered at 1, 2, and 4 kHz, were compared with the pure-tone threshold at the same frequencies. Data were analyzed with clinical decision theory, cumulative distributions, discriminant analyses, and logistic regressions. RESULTS: Using univariate analysis techniques, TEOAEs accurately identified auditory status at 2 and 4 kHz but were less accurate at 1 kHz. Test performance was best when audiometric thresholds between 20 and 30 dB HL were used as the criteria for normal hearing. TEOAE SNR resulted in better test performance than did TEOAE amplitude alone; this effect decreased as frequency increased. Multivariate analysis methods resulted in better separation between normal and impaired ears than did univariate approaches, which relied on only TEOAE amplitude or SNR when test frequency band and audiometric frequency were the same. This improvement in test performance was greatest at 1 kHz, decreased as frequency increased, and was negligible at 4 kHz. CONCLUSIONS: TEOAEs can be used to identify hearing loss in children under routine clinical conditions. Univariate tests accurately identified auditory status at mid and high frequencies but performed more poorly at lower frequencies. The decrease in performance as frequency decreases may be a result of increased noise at lower frequencies but also may be due to properties of the measurement paradigm ("QuickScreen," high-pass filter at 0.8 kHz), which would not be ideal for recording energy around 1 kHz. The improvement in test performance when SNR was used and the interaction of this effect with frequency, however, would be consistent with the view that test performance in lower frequencies is at least partially influenced by the level of background noise. Multivariate analysis techniques improved test performance compared with the more traditional univariate approaches to data analysis. An approach is provided that allows one to assign measured TEOAE amplitudes, SNRs, or outputs from multivariate analyses to one of three categories: response properties consistent with normal hearing; results consistent with hearing loss; hearing status undetermined.     

Thyroxine affects physiological and morphological development of the ear

The onset and development of distortion product otoacoustic emissions (DPE) representing cochlear amplifier activity were studied in neonatal hyperthyroid (n = 10) and control (n = 10) rat pups. These were compared to the onset and development of auditory nerve-brainstem evoked responses (ABR) representing overall cochlear function, and to morphological development of the ear. DPEs were recorded at an earlier postnatal age to high (8 kHz) frequencies and progressed to lower (3 kHz) frequencies with age. ABRs to high-intensity clicks were recorded at least 2 days before DPEs, although DPE onset at 8 kHz preceded adult-like ABR thresholds. Both ABR and DPEs appeared earlier in the hyperthyroid rats. Histological evidence showed earlier morphological development of the ear in these animals. ABR thresholds and DPE amplitudes matured at a slower rate in the experimental group despite their earlier onset. There was no difference in ABR and DPE thresholds between adult hyperthyroid and control rats. However, in the experimental group, DPEs had smaller amplitudes to high (70 dB SPL) and to low (50 dB SPL) stimulus intensities at low frequencies. Hence, despite thyroxine-injected rat pups having earlier onset of auditory structure and function (lower ABR thresholds and earlier functioning active cochlear amplifier), it appeared that neonatal hyperthyroidism affected the later state of the cochlea, such that DPEs, especially to low-frequency stimuli, were depressed during and after maturation.     

CD1 hearing-impaired mice. I: Distortion product otoacoustic emission levels, cochlear function and morphology

The levels of distortion product otoacoustic emissions (DPOAEs) were measured in a strain of hearing-impaired mutant mice (CD1) at various stages of outer hair cell impairment and compared to those of a control inbred strain (CBA/J). Parallel measurements of cochlear potentials and auditory brainstem evoked responses (ABRs) were performed and surface preparations of organs of Corti were observed using phalloidin staining of filamentous actin. Comparison of DPOAEs (elicited by stimulus levels of 60 and 70 dB SPL) with standard functional tests allowed the categorization of CD1 ears into two groups on the basis of the presence or absence of DPOAE, which corresponded to mean ABR thresholds greater or less than 40 dB nHL respectively. When adopting ABR threshold as the gold standard, this procedure yielded rates of false-positives and -negatives ranging from 5 to 16%. However, individual predictions of electrophysiological function from DPOAE levels were not accurate, owing to their large variance, and attempts to optimize stimulus levels did not reduce this variance. In contrast, the profiles of DPOAE level vs. f2 exhibited large correlations with ABR threshold profiles as a function of f2. It was also noteworthy that the mean levels of DPOAEs in CD1 mice recorded in frequency intervals with normal ABR thresholds were significantly smaller than those of CBA/J mice. Although hearing loss was revealed early both by DPOAEs and by other functional tests, surface preparations often remained normal until about 3-4 months of age.     

Changes in otoacoustic emissions in patients with idiopathic sudden deafness

Transiently click-evoked (TEOAE), distortion product (DPOAE) and spontaneous otoacoustic emissions (SOAE) were recorded and changes in these tests were studied during the recovery process in 15 cases of idiopathic sudden deafness (ISD). In all these cases the amplitudes of TEOAEs and DPOAEs increased concurrently with the recovery of the hearing threshold. Ears with ISD were not different in their OAE characteristics from ears with other forms of sensorineural hearing loss (SNHL). In 4 of the 15 cases, SOAEs could be detected when hearing had recovered. These results suggest that the function of outer hair cells (OHCs) had deteriorated when the hearing threshold was elevated and that OHC activity recovered as hearing improved to nearly normal levels in ISD cases with good outcome.     

The Precedence Effect in Three Species of Birds (Melopsittacus undulatus, Serinus canaria, and Taeniopygia guttata).

The perceived locations of paired auditory images, simulating direct sounds and their echoes, have been recently studied in budgerigars (Melopsittacus undulatus; M. L. Dent & R. J. Dooling, 2003a, 2003b). In this article, the authors extend those experiments to include measurements of the precedence effect using a discrimination paradigm in two additional bird species: canaries (Serinus canaria) and zebra finches (Taeniopygia guttata). Although time courses of summing localization, localization dominance, and echo thresholds were similar across all species, budgerigars had slightly higher overall levels of discrimination. The results from these experiments add further support that the precedence effect in birds is similar to that found in other animals and that the ability to suppress echoes that might degrade localization and auditory object perception may be a general property of the vertebrate auditory system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potential effects of managed care organizations in rural communities: a framework

OBJECTIVE: To define mechanisms accounting for transient deafness in three children (two siblings, ages 3 and 6, and an unrelated child, age 15) when they become febrile. DESIGN: Audiometric tests (pure-tone audiometry, speech and sentence comprehension), tympanometry, middle ear muscle reflex thresholds, otoacoustic emissions (OAEs), and electrophysiological methods (auditory brain stem responses [ABRs], sensory evoked potentials, peripheral nerve conduction velocities) were used to test the children when they were afebrile and febrile. RESULTS: ABRs, when afebrile, were abnormal with a profound delay of the IV-V and absence of waves I-III. The ABR in one of the children, tested when febrile, showed no ABR components. Measures of cochlear receptor function using OAEs were normal in both febrile and afebrile states. Cochlear microphonic potentials were present in the three children, and a summating potential was likely present in two. When afebrile, there was a mild threshold elevation for all frequencies in the 15-yr-old and a mild elevation of thresholds for just low frequencies in the two siblings. Speech comprehension in quiet was normal but impaired in noise. One of the siblings tested when febrile had a profound elevation (>80 dB) of pure-tone thresholds and speech comprehension was absent. Acoustic reflexes subserving middle ear muscles and olivocochlear bundle were absent when febrile and when afebrile. No other peripheral or cranial nerve abnormalities were found in any of the children. Sensory nerve action potentials from median nerve in one of the children showed no abnormalities on warming of the hand to 39 degrees C. CONCLUSION: These children have an auditory neuropathy manifested by a disorder of auditory nerve function in the presence of normal cochlear outer hair cell functions. They develop a conduction block of the auditory nerves when their core body temperature rises due, most likely, to a demyelinating disorder of the auditory nerve. The auditory neuropathy in the two affected siblings is likely to be inherited as a recessive disorder.     

Phenotypic patterns of distortion product otoacoustic emission in inbred and F1 hybrid hearing mouse strains

Distortion product otoacoustic emissions (DPOE) were obtained from five different hearing mouse groups: CBA/J, MOLF/Rk, ct (homozygous normal mice of the curly-tail stock), and the F1 hybrid offspring of the matings CBA/J x dn/dn and MOLF/Rk x dn/dn (dn/dn mice are the curly-tail stock with recessive deafness). The DPOE patterns of the CBA/J and ct strains were similar to each other and different from that of the MOLF/Rk. The two sets of F1 hybrid mice, (CBA/J x dn/dn)F1 and (MOLF/Rk x dn/dn)F1, were found to have significantly larger DPOE amplitudes than their hearing parent strains, MOLF/Rk and CBA/J, respectively. In addition, the DPOE amplitudes were greater for the offspring of the MOLF/Rk x dn/dn cross than for those of the CBA/J x dn/dn cross, even though they were lower for MOLF/Rk than for CBA/J. The distinct features of DPOE patterns among these five groups suggest that DPOE testing can be used for auditory phenotyping.     

Animal pharmacokinetics and interspecies scaling of Ro 25-6833 and related (lactamylvinyl)cephalosporins

To evaluate the potential of distortion product otoacoustic emissions (DPOAEs) in differential diagnosis of hearing loss, these were routinely measured in 232 ears of severe or profound sensorineural hearing loss. Normally recordable DPOAEs were found in 16 ears (8 patients) and the results were confirmed through retests after intervals; positive responses of transiently evoked otoacoustic emissions (TEOAEs) were additionally tested. The findings suggest that nerve deafness and hair cell deafness may be partly distinguishable.     

The Wolfram syndrome: diabetes mellitus, hypacusis, optic atrophy and short stature in STH deficiency

HISTORY AND CLINICAL FINDINGS: A 43-year-old man was known for 3 years to have diabetes mellitus. For 2 months before admission he had symptoms of hyperglycaemia with polyuria, polydipsia, weight loss, as well as impairment of vision and declining fitness. In addition to bilateral deafness he was clearly of normally proportioned short stature (150 cm). INVESTIGATIONS: The levels of blood sugar (221 mg/dl), HbA1c(10.2%), triglycerides (496 mg/dl) and cholesterol (323 mg/dl) were raised, while the concentration of somatotropic hormone was diminished, both before and after arginine administration. Fundoscopy revealed concentric diminution of the visual fields with left amblyopia. Visual evoked potentials and colour sense testing revealed bilateral optical atrophy, and the audiogram demonstrated deafness. These findings provided the diagnosis of Wolfram syndrome, namely insulin-dependent diabetes mellitus, deafness, optical atrophy and small stature with somatotropic hormone deficiency. TREATMENT AND COURSE: On insulin treatment the metabolic state became normal (HbA1c 7.5%, normal lipid profile). It was decided that the deficiency in somatotropic hormone regulation did not require treatment. CONCLUSION: Cardinal symptoms of the autosomally recessive Wolfram syndrome are insulin-dependent diabetes and optic nerve atrophy. Several types of hormonal abnormalities are associated with it, including a deficiency in the somatotropic axis. To obtain early and adequate hormonal substitution requires extensive endocrinological diagnosis of a disease which frequently becomes manifest in childhood or adolescence.     

Spontaneous otoacoustic emissions in preterm neonates: prevalence and gender effects

A number of lines of evidence indicate that the human cochlea is fully functional as a mature sound transducer by 6 months of age. However, information about the development of the active cochlear mechanisms and notably the development of outer hair cell (OHC) activity is yet incomplete. Recording and analysis of otoacoustic emissions (OAEs), probably generated by the OHCs of the organ of Corti, have led to a better understanding, in humans, of how sounds are analysed in the cochlea by means of active mechanisms. Evoked OAEs (EOAEs) and spontaneous OAEs (SOAEs), when they can be recorded in full-term and preterm neonates, show different characteristics from those in adults, suggesting that maturation of the peripheral auditory system is incomplete at birth. To learn more about this maturation, using the best-established facts concerning SOAEs in adults, such as their greater prevalence in females and also in right ears, SOAEs were studied in more detail in 81 preterm neonates, from 30 to 40 weeks of conceptional age, all presenting bilateral EOAEs according to objective criteria. The first finding of this study was that SOAEs existed and could be recorded as of 30 weeks of conceptional age in humans. Some SOAE characteristics in preterm neonates, such as prevalence, peak number and acoustic frequencies, showed similarity with full-term neonates. Comparison of other criteria between the two populations, such as greater SOAE prevalence in right ears and higher SOAE peak number in females, suggested that these developmental factors emerge around term in humans. Comparison of SOAE characteristics between male and female preterms suggested that male preterms were less advanced in peripheral auditory development than were female preterms.     

Auditory deprivation and recovery in adults with asymmetric sensorineural hearing impairment

The purpose of this investigation was to investigate (1) whether auditory deprivation effects are present in the poorer ears of adults with asymmetric sensorineural hearing impairment and (2) whether, if such effects are present, they can be reversed by amplification. Subjects were 16 males with asymmetric sensorineural hearing impairment, 8 of whom had never been aided, 6 of whom were aided monaurally at the initial test, and 2 of whom were unaided at the initial test but aided monaurally later on. Data were obtained from a retrospective review of records. The initial and retest (2-13 years post initial test) suprathreshold speech-recognition scores for 50-word, taped lists of the CID W-22 PB words were analyzed. The results revealed a significant difference between the initial and retest mean suprathreshold speech-recognition scores for the poorer ears of the unaided subjects. The results also revealed no significant change from the initial test to retest in six of the aided ears and significant improvement from the initial test to retest in the two of the aided ears. The findings are discussed with reference to the theory of auditory deprivation and recovery from auditory deprivation by amplification.     

Distortion product otoacoustic emissions for the assessment of auditory sensitivity

Distortion product otoacoustic emissions (DPOAEs) were evaluated in 494 normal and 506 cochlear-impaired human ears, to determine whether DPOAEs depend on factors such as background noise, the shape of the pure tone audiogram, sex and aging, and whether a DPOAE test can perform well in distinguishing normal-hearing from hearing-impaired ears. The amplitudes of DPOAEs were measured at the frequency of 2f1-f2 (f1 < f2, f2/f1 = 1.22, f2 at 1, 2 and 4 kHz) using as stimuli two pure tones at level of 70 dB from an ILO92 Otoacoustic Emission Analyzer. The correlation coefficients between the DPOAE level and the auditory threshold decreased as the background noise levels at 1 kHz and 2 kHz increased. Therefore, it appeared that ears with large background noise levels would be inadequate for the study of DPOAEs predicting the hearing state. The sensitivity (normal-hearing ears identified as normal hearing) and the specificity (hearing-impaired ears identified as hearing impaired) at the equal-sensitivity-specificity condition were 80.7-86.7% at 1, 2 and 4 kHz, and the areas under the receiver operating characteristic (ROC) curves, which were used to estimate the test performance, were 0.88 for 1 kHz, 0.91 for 2 kHz and 0.92 for 4 kHz. Since these results suggest that a DPOAE can be used as a reliable technique for objective auditory tests, it is thought that actual values (DPOAE level: 4.3 dB at 1 kHz, 5.0 dB at 2 kHz and 2.9 dB at 4 kHz) of false-positive (hearing-impaired ears identified as normal hearing) rates corresponding to 5% can be used in clinical evaluation to separate normal hearing from hearing-impaired ears. There was, however, a significant age effect at 4 kHz on DPOAEs in the ears with the same pure tone hearing thresholds, and the areas of the ROC curves in subjects ranging from 10 to 29 years old were larger than in subjects over 50 years (1 kHz: 0.88 to 0.94 versus 0.83 to 0.84, 2 kHz: 0.95 versus 0.89, 4 kHz: 0.95 to 0.96 versus 0.88 to 0.89). Therefore, it is thought that age-adjusted norms may be necessary for the accurate interpretation of DPOAE results.     

Subjective assessment of allergy relief following group hypnosis and self-hypnosis: a preliminary study

Distortion Product Otoacoustic Emissions (DPOEs) are otoacoustic emissions evoked by two pure equilevel tones (f1, f2) called primaries and are believed to provide frequency-specific information regarding cochlear function. We recorded DPOEs at 2f1-f2 frequency with a constant frequency ration (f2/f1 = 1.22) in 8 normal hearing subjects (16 ears, mean age 28 +/- 1.5) to establish the characteristics of these emissions in the adult population. DPOEs were measured at the following F2 frequencies and respective fp geometric mean frequencies: 696/632, 1001/904, 1501/1360, 2002/1809, 3003/2714, 4004/3626, 5005/4531 e 6006/5435 Hz. Detailed testing included the recording of DPOE "audiograms" and input-output functions depicting the relationship of the amplitudes of DPOE to primary-tone levels ranging from 25 to 70 dB SPL in 5 dB steps. The present findings are in good agreement with investigations based on evoked otoacoustic emissions published by other researchers. The average DPOE "audiograms" demonstrated a low-frequency maximum at 1501 Hz (f2)/1360 (fp) and a high-frequency peak at 5005 Hz (f2)/4531 (fp). The two maximum regions were separated by a minimum around 3003 Hz (f2)/2714 (fp). This study confirms the feasibility of DPOE measurements among adults and provide a normal baseline for this age group. DPOEs could be useful, in association with evoked otoacoustic emissions and with auditory brainstem responses, in obtaining a precise evaluation of the peripheral auditory system.