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PubMed1999

Auditory temporal processing impairment: neither necessary nor sufficient for causing language impairment in children.

Fourteen twin pairs, aged 8 to 10 years, were tested 3 times over 12 months; they included 11 children with language impairment (LI), 11 control children matched on nonverbal ability and age, and 6 co-twins who did not meet criteria for LI or control status. Thresholds were estimated for detecting a brief backward-masked tone (BM), detection of frequency modulation (FM), and pitch discrimination using temporal cues (deltaf0). Both BM and FM thresholds improved with training, and by the 2nd test session, FM thresholds were in the adult range. There were marked individual differences on BM and deltaf0 and, for both tasks, performance correlated with Tallal's Auditory Repetition Task administered 2 years previously. However, no auditory measure gave significant differences between LI and control groups; performance was influenced more by nonverbal than language ability. Some children did have a stable pattern of poor performance on certain auditory tasks, but their good FM detection raised questions about whether processing of auditory temporal information is abnormal. We found no evidence that auditory deficits are a necessary or sufficient cause of language impairments.

Adult↗

PubMed2001

Daily variation and appetitive conditioning-induced plasticity of auditory cortex receptive fields.

Long-term modification of cortical receptive field maps follows learning of sensory discriminations and conditioned associations. In the process of determining whether appetitive - as opposed to aversive - conditioning is effective in causing such plastic changes, it was discovered that multineuron receptive fields, when measured in rats under ketamine-sedation, vary substantially over the course of a week, even in the absence of classical conditioning and electrode movement. Specifically, a simple correlation analysis showed that iso-intensity frequency response curves of multiunit clusters and local field potentials recorded from auditory cortex are nonstationary over 7 days. Nevertheless, significant plastic changes in receptive fields, due to conditioned pairing of a pure tone and electrical stimulation of brain reward centres, are detectable above and beyond these spontaneous daily variations. This finding is based on a novel statistical plasticity criterion which compares receptive fields recorded for three days before and three days after conditioning. Based on a more traditional criterion (i.e. one day before and after conditioning), the prevalence of learning-induced changes caused by appetitive conditioning appears to be comparable to that described in previous studies involving aversive conditioning.

Acoustic Stimulation↗

PubMed2002

Response properties of neurons in the core of the central nucleus of the inferior colliculus of the barn owl.

The central nucleus of the inferior colliculus (ICC) is particularly important for the processing of interaural time differences (ITDs). In the barn owl, neuronal best frequencies in a subnucleus of the ICC, the ICCcore, span the animal's entire hearing range (approximately equal to 200-10 000 Hz). This means that low-frequency ITD-sensitive ICCcore neurons in the owl can be directly compared to ITD-sensitive mammalian ICC neurons with similar best frequencies as well as to the high-frequency ITD-sensitive neurons usually studied in owls. This report represents a first attempt to systematically describe important physiological properties of ICCcore neurons in the barn owl, with particular attention to the low-frequency region (< 2 kHz). Responses were obtained from 133 neurons or small clusters of neurons; recording sites were confirmed by histological reconstruction of electrode tracks based on electrolytic lesions. Iso-intensity frequency response functions were typically approximately equal to 1 octave wide in the low-frequency range and approximately equal to 1/3 octave wide in the high-frequency range. Most neurons were ITD-tuned; both noise and pure tone stimuli yielded periodic ITD tuning curves with several equivalent response maxima. In most cases ITD tuning curves had a response peak within the barn owl's physiological ITD range. ITD tuning widths were inversely correlated with neuronal best frequency. None of the ICCcore neurons studied were sensitive to interaural level differences. Monaural inputs to ICCcore cells were typically binaurally balanced, i.e. they exhibited similar response thresholds, dynamic ranges, slopes and saturation levels, for both left and right ear monaural stimulation.

Acoustic Stimulation↗

PubMed2002

Auditory event-related brain potentials in parents of children with specific language impairment.

Auditory event-related brain potentials evoked in response to tone stimuli and to speech stimuli were recorded in a group of parents of children with specific language-impairment and a group of parents of normally speaking children. The parents of the language-impaired children showed longer P3 latencies than the parental control group in the speech task requiring a phonological discrimination, but did not differ from the controls in the linguistically non-demanding tone discrimination task. The longer P3 latency was associated with a positive parental history of language delay. There were no group differences concerning the N1 component in any of the tasks. The findings indicate that parents of children with specific language impairment show signs of deficient late-stage perceptual higher order linguistic processing, whereas the earlier central sensory detection stage of the phonological information is no different from the controls. Our observations are particularly interesting with regard to a study of the children of these two parental groups, where the language-impaired children showed longer P3 latencies than controls in both a tone task and a speech task, whereas there were no differences between the children concerning the N1 component. We propose that deficient late-stage auditory higher order perceptual processing as indexed by the longer P3 latency to speech stimuli observed both in children with specific language-impairment and in their parents may represent a constitutional trait, contributing to the language acquisition difficulties in these children.

Adult↗

PubMed1998

[Visualization of central auditory processes with functional magnetic resonance tomography].

BACKGROUND: Central auditory processes can be visualized using functional MRI in a non-invasive manner and at high spatial resolution. Acoustic stimulation leads to an increase of blood flow of activated areas in the plane of the superior temporal gyrus. Radiologically, this may be visualized based on the long T2-relaxation time of oxyhemoglobin. PATIENTS: Ten normal-hearing subjects with ages between 28 and 38 years took part in the investigations. They received binaural, monaural right, and monaural left stimulation with pulsed sine tones of 1000 Hz at a pulse rate of 6 Hz and a sound pressure level of 100 dB SPL. Tonotopic organization of the auditory cortex was visualized using stimulation by pulsed sine tones of 500 Hz and 4000 Hz. RESULTS: Following monaural acoustic stimulation, increased activity of the contralateral auditory cortex could be demonstrated in 9 subjects. In one subject, bilateral activity was noted. Concerning the tonotopic organization of the auditory cortex, we could show that the higher frequencies were localized more medially and anteriorly; the lower frequencies were localized more laterally and posteriorly in the superior temporal gyrus. However, considerable overlap was noted. CONCLUSIONS: The overlap of the different frequencies could explain the controversial discussion of the tonotopic organization of the auditory cortex. The results of the monaural acoustic stimulation show clearly the predominant signal increase of contralateral areas in the primary auditory cortex. These results confirm the opinion of the current textbooks that the fiber of the auditory pathways mostly cross. Further investigations using functional MRI are necessary for better understanding of physiological and pathophysiological central-auditory processes.

Acoustic Stimulation↗

PubMed1994

[3-dimensional representation of transient evoked otoacoustic emissions].

A new method for the transformation of TEOAE signals into 3-dimensional diagrams is presented. The special transformation algorithm is based on a latency related frequency analysis of the cochlear response. The analysis and presentation are implemented in a C-programme. In a first clinical study 390 TEOAE signals from ears with and without hearing impairment were evaluated. For normal hearing the 3-dimensional diagram of TEOAE-signals is characterised by a typical wave form: with increasing frequency the latency of the cochlear response decrease. In the case of hearing loss there is an overall tendency to increasing wave latencies in comparison to normal hearing. An additional wave in the 3-dimensional diagrams of ears with tinnitus was observed. This characteristic is interpreted as an indicator of cochlea dysfunction. The 3-dimensional diagram promises to give a new aspect in the clinical interpretation of click-evoked otoacoustic emissions.

Adolescent↗

PubMed1994

[Evoked otoacoustic emissions and middle ear function].

Transiently evoked otoacustic emissions (TEOAE) recorded in 98 ears were compared depending on the results of tympanometry. The values of middle ear pressure in patients without detectable TEOAE are significantly smaller compared to those of patients with detectable TEOAE. In cases of detectable TEOAE, the amplitudes and frequency components were compared to the results of tympanometry. When maximal compliances are shifted towards negative values of middle ear pressure, the amplitudes of TEOAE are reduced with a loss of low frequency components. Small compliance values result in reduced amplitudes of TEOAE with the loss of low frequency components. By means of cluster analysis in the scatter plot of middle ear compliance and pressure, a classification is obtained separating two groups representing significantly groups of patients with and without detectable TEOAE. Summing up, it must be stated that there is an effect of middle ear function on TEOAE which must be taken into consideration when TEOAE are used in clinical application.

Acoustic Impedance Tests↗

PubMed1994

[Temporal resolution with a hearing aid in hearing impaired persons].

The purpose of hearing aid fitting is to improve the communication of the hearing impaired. Despite rigorous efforts to optimize hearing aid fitting there are still some patients who remain unsatisfied. The subject of research was to find improved methods of measuring, to increase the correlation between subjective information from the patient and objectively measurable data. With this goal in mind the variation of temporal resolution in hearing aid fitting was investigated in 88 patients comparing unaided and aided hearing basing on the method of determining the temporal resolution factor TRF at 500 Hz, 1500 Hz and 4000 Hz under free sound field conditions, as previously described by Schorn and Zwicker. The method is based on masking period patterns but measures only their maximum and minimum using continuous and 30-Hz square-wave amplitude modulated masking noise. The following three values of interest are measured: Threshold in quiet using interrupted continuous tones (500 ms on, 500 ms off) with the masker off; threshold masked by a continuous masker (octave-wide continuous noise) and threshold masked by a rectangulary modulated masker using 14 Hz, so that periods of 72 ms and pauses of 36 ms occur. TRF was defined as the ratio between the level differences derived from the three measured values. For normal hearing subjects this factor is about 1. The results show significant variation of the TRF comparing the data of the patients with and without hearing aids. The values for TRF unaided were 0.5 and 0.6 as well as under hearing aid.(ABSTRACT TRUNCATED AT 250 WORDS)

Audiometry, Pure-Tone↗

PubMed1994

[Effect of sedation on otoacoustic emissions].

Even though the measurement of transitory evoked otoacoustic emissions (TEOAE) is easy and without problems in babies, sedation might be necessary in children aged between 1 and 4 years. As only very little information is available on the influence of a sedation on the TEOAE, the present study was performed. 35 normal hearing patients who were treated with benzodiazepines as a premedication for an operation were included in the investigation. 15 patients received diazepam and 20 were given flunitrazepam in a dosage of 10 and 1 mg respectively. The TEOAE were measured using the ILO 88 system by Bray and Kemp 1 day before, 1 hour after and 3 days after drug intake. 10 additional subjects of whom measurements were taken at the same time intervals served as controls. No statistically significant changes could be detected before and after drug treatment in respect of amplitudes of the TEOAE and frequency of maximum amplitudes. Hence, we conclude that sedation as used in this study must be considered negligible when measuring TEOAE.

Acoustic Stimulation↗

PubMed1997

[Possibility for quantitative and frequency-specific assessment of auditory threshold with otoacoustic emissions].

BACKGROUND: Otoacoustic emissions can be used to study cochlear function in a non-invasive manner. They are an effective clinical tool for infant hearing screening. The purpose of this study was to determine their utility for a frequency-specific and quantitative estimation of the hearing threshold. METHODS: Transiently evoked otoacoustic emissions (TEOAE) and distortion-product emissions (DPOAE) were recorded from 16 normal and 86 hearing impaired ears and correlated with their hearing threshold between 0.5 and 6.0 kHz. RESULTS: The correlations of TEOAE and the hearing threshold ranged from 0.53 (0.5 kHz) to 0.69 (6.0 kHz), of the DPOAE from 0.51 (0.5 kHz) to 0.83 (6.0 kHz). Based on the optimal correlating OAE frequency we tried to predict the hearing threshold. We obtained 95% prediction intervals for TEOA between 19 dB (1.0 kHz) and 39 dB (4.0 and 6.0 kHz), for DPOAE between 21 dB (1.0) and 34 dB (3.0 and 4.0 kHz). CONCLUSION: Despite their clinically irrelevant greater prediction intervals at the low frequencies, our results suggest that DPOAEs are generally more valuable for the frequency-specific estimation of the hearing threshold. Prediction intervals may improve the interpretation of OAEs.

Adolescent↗

PubMed1995

[Diagnosis of endolymphatic hydrops with low tone masked otoacoustic emissions].

BACKGROUND: A new method of diagnosis of endolymphatic hydrops by recording low-tone masked evoked otoacoustic emissions (TEOAE) is presented. METHODS: A short acoustic stimulus and a masker tone of 30 Hz are applied in an adjustable phase relation simultaneously to the same ear. In the normal hearing ear the masker shows little influence on the TEOAE at 0 degrees, whereas the suppression at phase 270 degrees (maximal rarefaction at the eardrum) is nearly complete. However, in cases of endolymphatic hydrops this masking effect is reduced or absent, indicating impaired mobility of the basilar membrane. RESULTS: The masked TEOAE were recorded of patients with normal hearing, Menière's disease, and sudden hearing loss without vertigo. In Menière cases with supposed endolymphatic hydrops, the amplitude modulation of the emissions was found to be much less than in the other groups. CONCLUSIONS: Where TEOAE can be recorded, low-tone masking is a quick, objective, and noninvasive method for the diagnosis of endolymphatic hydrops.

Acoustic Stimulation↗

PubMed1993

[Value of in situ measurement for evaluating effective hearing aid amplification at high sound pressure levels].

A careful hearing aid fitting requires consideration of various characteristics of inner ear pathology. The recruitment phenomenon restricts the dynamic range of the impaired hearing and this increase the demands on the hearing aids for a satisfactory correction of the frequency characteristics as well as for an intensity reduction at higher sound pressure level SPL. For years data from coupler or KEMAR (Knowles Electronics Manikin of Acoustical Research) have served to estimate the real ear gain of a hearing aid at higher input levels. In previous papers we reported on some of the differences between coupler measurement and probe tube measurement. The object of this study was to investigate the differences between these two methods at higher input SPL. Therefore, we measured the real ear insertion gain as well as the output characteristics with a 2 cm3 coupler in 80 patients at input levels of 60 dB, 80 dB and 100 dB. The results show differences between the two methods up to 30 dB in both directions in the single patient. Furthermore, the highest compression rate was found in the middle and high frequency range which are crucial for speech discrimination. Consequently, probe tube measurement should be used not only to adjust the frequency characteristics of the hearing aid but also to characterise the real effect of Automatic Gain Control AGC and Peak Clipping PC on insertion gain at higher input SPL. Multichannel hearing aids should be used whenever possible to reduce the disturbances to speech discrimination at low frequencies.

Hearing Aids↗

PubMed2003

Effects of vocal training on the acoustic parameters of the singing voice.

Vocal training (VT) has, in part, been associated with the distinctions in the physiological, acoustic, and perceptual parameters found in singers' voices versus the voices of nonsingers. This study provides information on the changes in the singing voice as a function of VT over time. Fourteen college voice majors (12 females and 2 males; age range, 17-20 years) were recorded while singing, once a semester, for four consecutive semesters. Acoustic measures included fundamental frequency (F0) and sound pressure level (SPL) of the 10% and 90% levels of the maximum phonational frequency range (MPFR), vibrato pulses per second, vibrato amplitude variation, and the presence of the singer's formant. Results indicated that VT had a significant effect on the MPFR. F0 and SPL of the 90% level of the MPFR and the 90-10% range increased significantly as VT progressed. However, no vibrato or singers' formant differences were detected as a function of training. This longitudinal study not only validates previous cross-sectional research, ie, that VT has a significant effect on the singing voice, but also it demonstrates that these effects can be acoustically detected by the fourth semester of college vocal training.

Acoustics↗

PubMed1987

Relative effectiveness of three stimulus variables for locating a moving sound source.

A study is reported in which it is shown that observers can use at least three types of acoustic variables that indicate reliably when a moving sound source is passing: interaural temporal differences, the Doppler effect, and amplitude change. Each of these variables was presented in isolation and each was successful in indicating when a (stimulated) moving sound source passed an observer. These three variables were put into competition (with each indicating that closest passage occurred at a different time) in an effort to determine their relative importance. It was found that amplitude change dominated interaural temporal differences which, in turn, dominated the Doppler effect stimulus variable. The results are discussed in terms of two interpretations. First, it is possible that subjects based their judgements on the potential discriminability of each stimulus variable. However, because the stimuli used involved easily discriminable changes, subjects may instead have based their judgements on the independence of a stimulus variable from different environmental situation conditions. The dominance ordering obtained supports the second interpretation.

Attention↗

PubMed1987

Simulation of the response of a multichannel nerve array to pulse shapes produced by single-channel electrostimulation.

Results of experiments on single-channel electrostimulation of the cochlea which throw light on the performance of the central auditory nervous system (CANS) have recently been reported by Dobie and Dillier. Trains of pulses with different rise times could be distinguished by subjects with cochlea implants, even though time differences involved were very small. It was suggested by the authors that the information is carried to the CANS by an array of nerve fibres with characteristic time differences. In the present paper, simulations produced by means of a nerve model are reported and used to compute the patterns of action potentials evoked on the nerve array by different pulse trains. The changes in the patterns of the nerve responses resulting from the shape variations which have to be perceived by the CANS are examined.

Cochlear Implants↗

PubMed2003

"Seeing things in my head": a synesthete's images for music and notes.

We explored synesthetic experiences (photisms) elicited by music and notes for GS, a 22-year-old female college student, who is a genuine digit synesthete (Mills et al 1999 Cognitive Neuropsychology 16 181-191). After extensive interviews, we conducted five studies using synthesizer notes in different octaves and in different instrument sounds. GS described, drew, or selected her photisms from alternatives. The results were: (a) her photisms had shape, color, movement, and texture: (b) different instruments had photisms with different shapes and families of instruments had similar shapes; (c) low-pitched notes were darker and larger than high notes; (d) instrument and pitch affected each other; (e) a given note was perceived as darker after a high note than after a low note; and (f) GS's drawings of notes became more consistent with repeated trials. Theoretical observations are discussed on the basis of these results.

Acoustic Stimulation↗

PubMed2003

Musical alexia for rhythm notation: a discrepancy between pitch and rhythm.

In the process of reading music, the reading of rhythm and pitch might be differentiated, although there is no evidence of this to date. There have been cases of disorders restricted to the reading of pitch, but none in which the disorder has been restricted to the reading of rhythm. We present a case of musical alexia and agraphia with Wernicke's aphasia. An in-depth assessment of the subject's musical reading ability showed that her musical alexia was restricted to unfamiliar melodies. When a melody was divided into rhythm elements and pitch elements, pitch reading was preserved, but rhythm reading was severely disturbed. This is the first case reported of a disorder restricted to rhythm reading, and suggests the independence of rhythm reading and pitch reading.

Aphasia, Wernicke↗

PubMed2000

Cortical mechanisms for auditory spatial illusions.

Frequency transformation by the external ears provides the spectral cues for localization of broadband sounds in the vertical plane. When human subjects listen to spectrally-impoverished narrowband sounds presented in a free field, the perceived locations vary with the centre frequency and are largely independent of the actual source locations. The present study explored the substrate of spatial illusion by examining the responses of cortical neurons to narrowband stimuli. Single-unit responses were recorded in area A2 of anaesthetized cats. Broadband noise bursts were presented at 14 locations in the vertical median plane, from 60 degrees below the front horizon, up and over the head, to 20 degrees below the rear horizon. Narrowband (1/6-oct) noise bursts were presented at + 80 degrees elevation. An artificial neural network was trained to recognize the spike patterns elicited by broadband noise and, thereby, to register the spike patterns with sound-source elevation. When the trained network was presented with neural responses elicited by narrowband noise, the elevation estimated by the neural network varied with the centre frequency of the narrowband stimuli. Consistent with psychophysical results in human, the locations associated with a given centre frequency could be predicted by comparing the stimulus spectrum with the directional transfer functions of the cat's external ear. The results support the hypothesis that full spike patterns (including spike counts and spike timing) of cortical neurons code information about sound location and that the auditory cortical neurons play a pivotal role in localization behaviour.

Acoustic Stimulation↗