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PubMed1975

Susceptibility to delayed auditory feedback and dependence on auditory or oral sensory feedback.

Studies of the delayed auditory feedback (DAF) effect have consistently reported marked individual differences in susceptibility to DAF among normal speakers. It has been suggested that speakers showing extreme susceptibility to DAF may be differentially dependent on auditory feedback in regulating their speech production. Assuming this is the case, then a reduction in sensory feedback would also be expected to produce differential effects on these speakers. To test this hypothesis, normative data on the actual range of susceptibility to 180 msec DAF were first obtained from a group of 400 normal male speakers. Subjects from the extremes of this distribution were then tested under conditions that selectively reduces sensory feedback. Auditory masking, whispering and local anaesthesia were used separately and in combination to achieve a reduction in one or more feedback channels (air-conducted, bone-conducted and oral sensory feedback). The results obtained did not support the feedback dependence hypothesis. Measures of reading duration, disfluency and correct syllabel rate revealed similar changes in the speech of high and low susceptible speakers when auditory and/or oral feedback was reduced. Alternative explanations of individual differences in DAF susceptibility are considered.

Adult↗
PubMed1994

After-discharges in the auditory cortex of the mustached bat: No oscillatory discharges for binding auditory information.

Action potentials of single or multi-neurons were recorded from the DSCF, FM-FM and DF areas in the auditory cortex of the mustached bat to study stimulus-induced neural oscillation in the auditory system. Out of 125 neurons 120 recorded in these three areas showed after-discharges to a best stimulus. Durations of after-discharges of 120 neurons ranged between 4.8 and 217 ms. In the remaining 5 neurons, the duration of the discharges was shorter that of the stimulus. The PST histograms displaying responses of these 125 neurons showed no oscillatory component locked to the stimulus. 98% of the autocorrelograms of responses (122/125) showed no sign of oscillation, but the remaining two percent showed a very weak oscillatory component that was not stimulus-locked. The duration of the after-discharges had no correlation with the best delay or cortical depth of neurons. After-discharges are common in the auditory cortex of the mustached bat, but oscillatory discharges are very rare, so that neural oscillations play no role in binding various types of biosonar information processed in the different 'specialized' areas in the auditory cortex.

Action Potentials↗
PubMed2004

Interaction between auditory and visual stimulus relating to the vowel sounds in the auditory cortex in humans: a magnetoencephalographic study.

We investigated the interaction between auditory and visual stimulus relating to the vowel sounds in the auditory cortex in humans, using magnetoencephalography. We compared the difference in the main component, M100 generated in the auditory cortex, in terms of peak latency, amplitude, dipole location and moment, following the vowel sound_/a/_between two conditions: (1) showing a face with closed mouth; and (2) showing the same face with mouth movement appearing to pronounce/a/using an apparent motion method. We found no significant difference in the M100 component between the two conditions within or between the right and left hemispheres. These findings indicated that the vowel sound perception in the auditory cortex, at least in the primary processing stage, was not affected by viewing mouth movement.

Acoustic Stimulation↗
PubMed1997

Human auditory cortex is activated by omissions of auditory stimuli.

Cortical signals associated with infrequent tone omissions were recorded from 9 healthy adults with a whole-head 122 channel neuromagnetometer. The stimulus sequence consisted of monaural (left or right) 50-ms 1-kHz tones repeated every 0.2 or 0.5 s, with 7% of the tones randomly omitted. Tones elicited typical responses in the supratemporal auditory cortices. Omissions evoked strong responses over temporal and frontal areas, independently of the side of stimulation, with peak amplitudes at 145-195 ms. Response amplitudes were 60% weaker when the subject was not attending to the stimuli. Omission responses originated in supratemporal auditory cortices bilaterally, indicating that auditory cortex plays an important role in the brain's modelling of temporal characteristics of the auditory environment. Additional activity was observed in the posterolateral frontal cortex and in the superior temporal sulcus, more often in the right than in the left hemisphere.

Acoustic Stimulation↗
PubMed1980

Auditory function in newborn intensive care unit patients revealed by auditory brain-stem potentials.

The relations between clinical illness and auditory response (as revealed by auditory brain-stem potentials) were prospectively studied in a neonatal intensive care unit. Forty-nine tests were performed on 29 infants with gestational age 24 to 43 weeks and birth weight 530 to 3,380 gm. Auditory test results were classified as pass or fail, depending on the presence or absence of wave V at a latency of 7 to 11 ms in response to clicks 60 dB above the normal adult threshold. Six patients failed and 23 patients passed. The failures were not correlated with excessive noise exposure or ototoxic medication. Five of the patients who failed had intracranial hemorrhage. Routine screening of infants in the NICU for auditory impairment is a clinically feasible and useful procedure.

Brain Stem↗
PubMed2000

The effect of interstimulus intervals and between-block rests on the auditory evoked potential and magnetic field: is the auditory P50 in humans an overlapping potential?

OBJECTIVE: The human auditory P50 may consist of overlapping potentials. To test this hypothesis, we manipulated interstimulus intervals (ISIs) and between-block rests, and recorded the P50, P50m, N100 and the N100m simultaneously. METHODS: Subjects were 12 right-handed healthy adults. Four conditions included: (1) 1.5 s/rest, (2) 1.5 s/successive, (3) 0.5 s/rest, and (4) 0.5 s/successive. Auditory stimuli were presented a total of 880 times for each condition. Auditory evoked potentials and magnetic fields were recorded. We examined the P50, N100, P50m, N100m and dipoles of the P50m and the N100m. RESULTS: There was no significant effect of the ISI on the P50 amplitudes, but the P50m amplitudes in the 0.5 s ISI conditions were significantly smaller than those in the 1.5 s ISI conditions. The N100 and the N100m amplitudes in the 0.5 s ISI conditions were significantly smaller than those in the 1.5 s ISI conditions. The N100 and the N100m amplitudes in the resting conditions were significantly larger than those in the successive conditions. The P50m dipoles were slightly deeper and more anterior than those of the N100m in primary auditory cortex. CONCLUSIONS: Central structures other than supratemporal cortex contribute to the P50 and that the P50 in humans represents overlapping potentials.

Acoustic Stimulation↗
PubMed1977

Auditory-visual interactions and the correspondence between perceived auditory space and perceived visual space.

Changes in the physical rate of a clicking or fluttering sound caused changes in the rate at which a simultaneously viewed light appears to flicker, even though the physical flicker rate remains constant. Perceived flicker rate increases in response to a rate of change of flicker frequency, and this auditory 'driving' does not depend on whether the auditory and visual sources have the same location. Visual evoked potentials do not correlate with 'driving'. Thus, the effect of auditory flutter upon perceived visual frequency is not due to the properties of Morrell-type bimodal neurons, nor does it reflect the activities of neurons responsible for maintaining correspondence between perceived auditory space and perceived visual space. The effect is possibly due to modification of a subjective criterion rather than, as previously suggested, to the entrainment or time-locking of physiological signals in the visual pathway.

Auditory Perception↗
PubMed1977

The relation of auditory, visual, and auditory-visual matching to reading performance of Israeli children.

Six same-different matching tests, both verbal and nonverbal, in three modalities, along with a set of reading tests, were administered to 120 Israeli children in second, third, and fourth grade. The main effect of all S variables, except sex (grade, socioeconomic level, and ability) were significant, as were the test factors of modality (visual, auditory, cross-modal) and form (verbal-nonverbal), but interactions between S and test factors were small. Multiple regression analysis revealed that overall matching test scores accounted for 35% of the variance in reading scores, although the additional contribution of specific subtests was negligible. Performance on the visual-visual tests was virtually perfect. Auditory-auditory matches were more difficult than auditory-visual matches with nonverbal stimuli, while the reverse was true with verbal stimuli.

Auditory Perception↗
PubMed2000

Visual cognitive tests, central auditory function and auditory communication.

A cognitive, text-based test battery, presented as text on a computer screen (TIPS), was used to assess properties of central cognitive processing relevant for visual and audiovisual speech comprehension. TIPS was compared and contrasted with another, purely auditory, battery, ACE, aimed at assessing afferent (A), central (C) and efferent (E) auditory communicative functions. The results show that there is no overlap with the 'A' component, but some overlap between TIPS parameters and the 'C' component, especially when the auditory-language tests are used in the C estimate. However, the TIPS parameters show high correlations with the 'E' component (i.e. measuring output and phonological parameters), suggesting that the efferent component may be composed of an interesting central feature. TIPS parameters do not fare as well in the predictions of the auditory ecological test performances, but the ACE parameters do, especially when organized according to a cognitive complexity parameter. In order to optimize the conceptual and practical benefit of the TIPS and ACE concepts, TIPS needs to be adapted auditorily and ACE tests need to be audiovisual. These developments will become important for ecological audiology.

Adult↗
PubMed2001

Effects of the auditory stimuli of an auditory evoked potential system on levels of consciousness, and on the bispectral index.

Investigators in the field of depth of anaesthesia monitoring sometimes measure the auditory evoked potential (AEP) and the Bispectral Index (BIS) concurrently. However, the auditory stimuli required to generate an AEP may increase the level of consciousness, and cause an increase in the BIS. They may also alter the BIS by producing phase-locked harmonics in the surface electroencephalogram. The aim of this study was to determine if AEP stimuli have clinically significant effects on levels of consciousness and BIS values during sedation and general anaesthesia. Ten healthy adult patients were studied by measuring and recording the BIS for 6 epochs of 5 min each. The first 3 epochs took place during steady-state sedation, during which time the Observer's Assessment of Awareness/Sedation (OAA/S) score was also measured. The second 3 epochs took place during steady-state anaesthesia. During alternate epochs, patients were subjected to the auditory stimuli generated by an AEP system. The auditory stimuli were not associated with a change in BIS values (during sedation and anaesthesia) or OAA/S scores (sedation).

Acoustic Stimulation↗
PubMed2000

Congenital auditory deprivation reduces synaptic activity within the auditory cortex in a layer-specific manner.

The present study investigates the functional deficits of naive auditory cortices in adult congenitally deaf cats. For this purpose, their auditory system was stimulated electrically using cochlear implants. Synaptic currents in cortical layers were revealed using current source density analyses. They were compared with synaptic currents found in electrically stimulated hearing cats. The naive auditory cortex showed significant deficits in synaptic activity in infragranular cortical layers. Furthermore, there was also a deficit of synaptic activities at longer latencies (>30 ms). The 'cortical column' was not activated in the well-defined sequence found in normal hearing cats. These results demonstrate functional deficits as a consequence of congenital auditory deprivation. Similar deficits are likely in congenitally deaf children.

Animals↗
PubMed1989

The clinical assessment of obscure auditory dysfunction--1. Auditory and psychological factors.

We define obscure auditory dysfunction (OAD) as the clinical presentation of reported difficulty understanding speech in the presence of noise accompanied by clinically "normal" hearing thresholds, and no other obvious cause. The term deliberately avoids particular pathophysiological connotations. A detailed characterization of such patients was undertaken as the basis for future diagnosis and management of OAD by clinicians. Twenty patients were compared with 20 pairs of controls (matched for age, sex, educational level, and noise exposure) on tests of auditory, linguistic, and psychological function. Patients showed a genuine performance deficit on a speech-in-noise task, due in part to minor auditory dysfunction and poor linguistic ability. Their high level of self-rated disability and handicap cannot, however, be entirely explained by this genuine deficit. An anxious personality and a history of otological symptoms typified the patient group; either or both have presumably contributed to patients' seeking of medical or audiological advice. OAD is thus a multifactorial syndrome with contributions from auditory, psychological, and linguistic factors. The variance in (and correlation between) performance levels on two sentence-in-noise tests, present only within the patient group, indicates that these patients are not a homogenous group.

Adolescent↗
PubMed2006

Auditory-nerve first-spike latency and auditory absolute threshold: a computer model.

A computer model of the auditory periphery was used to address the question of what constitutes the physiological substrate of absolute auditory threshold. The model was first evaluated to show that it is consistent with experimental findings that auditory-nerve fiber spikes can be predicted to occur when the running integral of stimulus pressure reaches some critical value [P. Heil and H. Neubauer, J. Neurosci. 15, 7404-7415 (2001)]. It was then modified to examine two ways in which the accumulation and clearance of receptor presynaptic calcium might explain this effect. Both methods gave results that matched the animal data. It was also shown how the rate of clearance of presynaptic calcium could be used to explain the origin of differences between low and high spontaneous-rate fiber types. When spiking activity is aggregated across a number of similar high spontaneous-rate fibers and used as the input to a model of a cochlear nucleus coincidence neuron, its response can be used to judge whether or not a stimulus is present. A simulated psychophysical experiment then demonstrated that this simple decision procedure can reproduce measurements of absolute auditory threshold for tones in quiet where the threshold is a joint function of both time and level.

Acoustic Stimulation↗
PubMedDate not supplied

Temporal relationship between the auditory brainstem response and focal responses of auditory nerve root and cochlear nucleus during development in the tammar wallaby (Macropus eugenii).

Thirty-two pouch-young tammar wallabies were used to discover the generators of the auditory brainstem response (ABR) during development by the use of simultaneous ABR and focal brainstem recordings. A click response from the auditory nerve root (ANR) in the wallaby was recorded from postnatal day (PND) 101, when no central auditory station was functional, and coincided with the ABR, a simple positive wave. The response of the cochlear nucleus (CN) was detected from PND 110, when the ABR had developed 1 positive and 1 negative peak. The dominant component of the focal ANR response, the N1 wave, coincided with the first half of the ABR P wave, and that of the focal CN response, the N1 wave, coincided with the later two thirds. In older animals, the ANR response coincided with the ABR's N1 wave, while the CN response coincided with the ABR's P2, N2 and P3 waves, with its contribution to the ABR P2 dominant. The protracted development of the marsupial auditory system which facilitated these correlations makes the tammar wallaby a particularly suitable model.

Animals↗
PubMed2006

Auditory outcomes in tumor vs. nontumor patients fitted with auditory brainstem implants.

Auditory brainstem implants (ABIs) are currently indicated for patients older than 12 years with neurofibromatosis type 2 (NF2) who had bilateral schwannoma removed. Over the last 10 years, we have extended the indications for ABIs to nontumor children and adult patients with cochlear or cochlear nerve injuries or malfunctions who would not benefit from a cochlear implant. We have provided ABIs for patients with cochlear nerve aplasia and other injuries, and patients in whom any benefit was, or would be, severely compromised as in extensive cochlear ossification. In the present chapter we report our recent findings in adult ABI patients and compare the psychophysical and speech perception outcomes in tumor with those in nontumor patients. We demonstrate that the ABI can stimulate the central auditory system in a way that gives the ability of open set speech understanding, and can thus be indicated in nontumor adult patients who are not candidates for a cochlear implant. From April 1997 to January 2006, a total of 80 patients, 62 adults and 18 children, were fitted with ABIs in the University of Verona ENT Department; age ranged from 14 months to 70 years. Twenty-six patients had NF2 with bilateral vestibular schwannoma removal, and 54 had nontumor diseases of the cochlear nerve or cochlea. The retrosigmoid approach was used in all patients. All patients had a functioning implantation, and no complications were observed during the operation, activation as well as long-term use of the ABI. All patients, except 1 (NF2), reported auditory sensations with activation of various numbers of electrodes (from 5 to 21). Different electrodes elicited different pitch sensations. At 1 year after implantations nontumor adults scored from 12 to 100% in open set speech perception tests (average 59%), and tumor (NF2) patients scored from 5 to 30% (average of 11%). The differences between these results are statistically significantly (p < 0.01). To investigate the cause of the differences in performance between tumor and nontumor ABI recipients, a series of psychophysical tests were done consecutively in 39 adult patients with implants (25 nontumor and 14 tumor patients) from May 1999 to April 2004 and with a follow-up of at least 1 year. The outcome of this study shows that: (1) The ABIs allow most tumor and nontumor patients to experience improved communication as well as awareness of environmental sounds. (2) Nontumor patients had better hearing outcomes than tumor patients when the variation in the auditory benefit with the ABI in relation to the patient's underlying pathological conditions were taken into consideration. (3) A significant number of nontumor patients are able understand speech at a level comparable to that of the most successful cochlear implant users including conversational telephone use. (4) The ABI represents the tool for hearing rehabilitation in patients with profound hearing loss who cannot be fitted with cochlear implants.

Adolescent↗
PubMed1992

Auditory and psychological factors in 'auditory disability with normal hearing'.

Patients who have 'Auditory Disability with Normal Hearing' (ADN) complain of hearing difficulties even although their hearing is audiometrically 'normal'. The auditory and psychological factors involved in ADN have been investigated by comparing 20 patients of employment age with 20 controls (matched for age, sex and socioeconomic group) on appropriate auditory tests and questionnaires. From the results it was concluded that both auditory and psychological factors are involved in ADN. The principal finding was that as a result of their problems with discriminating speech in noise, individuals with ADN have a tendency to anxiety, depression and loneliness. In addition the otological history of an individual was found to be important in the development of ADN. Finally, it was suggested that bad coping strategies may lead to increased anxiety in those with ADN.

Adaptation, Psychological↗
PubMed2005

Intraoperative auditory brainstem responses in patients with cerebellopontine angle meningiomas involving the inner auditory canal: analysis of the predictive value of the responses.

OBJECT: Meningiomas of the cerebellopontine angle (CPA) can either arise from or secondarily grow into the inner auditory canal (IAC). This location may have a great impact on hearing function following surgery to remove these lesions. The aim of this retrospective study was to investigate the reliability and predictive importance of auditory brainstem responses (ABRs) for the determination of postoperative auditory function in patients with CPA meningiomas in comparison with results obtained in patients who undergo surgery for vestibular schwannomas. METHODS: In a consecutive series of 1800 meningiomas surgically treated between 1978 and 2002, 421 lesions were located in the CPA. In 38 patients with CPA meningiomas involving the IAC, the findings of intraoperative ABR monitoring and the hearing status of each patient before and after surgery were retrospectively analyzed. On analysis, ABR monitoring demonstrated stable findings in 24 patients throughout tumor resection and fluctuating signals in 10 patients. Among the 24 patients with stable ABRs, postoperative hearing function improved in three patients, remained the same in 15, and worsened in six patients, including one patient who displayed postoperative deafness. There was even one patient recovering from preoperative deafness. Among the 10 patients with unstable ABRs, intermittent decreases in amplitude and deformations of variable duration in the ABR wave were noted. The risk of deafness was considerably higher in patients with prolonged phases of intermittent ABR deterioration. CONCLUSIONS: The presence and absence of ABRs during surgery for CPA meningiomas reliably predicted the presence and absence of postoperative auditory function. Intermittent deterioration of ABRs may result in postoperative deafness, depending on the duration of these events during surgery. Improvements in hearing are only seen when the ABRs are stable for amplitudes and latencies throughout surgery.

Adult↗
PubMed1992

Visual projections routed to the auditory pathway in ferrets: receptive fields of visual neurons in primary auditory cortex.

How does cortex that normally processes inputs from one sensory modality respond when provided with input from a different modality? We have addressed such a question with an experimental preparation in which retinal input is routed to the auditory pathway in ferrets. Following neonatal surgical manipulations, a specific population of retinal ganglion cells is induced to innervate the auditory thalamus and provides visual input to cells in auditory cortex (Sur et al., 1988). We have now examined in detail the visual response properties of single cells in primary auditory cortex (A1) of these rewired animals and compared the responses to those in primary visual cortex (V1) of normal animals. Cells in A1 of rewired animals differed from cells in normal V1: they exhibited larger receptive field sizes and poorer visual responsivity, and responded with longer latencies to electrical stimulation of their inputs. However, striking similarities were also found. Like cells in normal V1, A1 cells in rewired animals exhibited orientation and direction selectivity and had simple and complex receptive field organizations. Furthermore, the degree of orientation and directional selectivity as well as the proportions of simple, complex, and nonoriented cells found in A1 and V1 were very similar. These results have significant implications for possible commonalities in intracortical processing circuits between sensory cortices, and for the role of inputs in specifying intracortical circuitry.

Animals↗