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PubMed1981

Cochlear responses to dynamic click patterns in the guinea pig.

Fast cochlear adaptation, expressed as percent inhibition of the summed action potential, is studied from the guinea pig cochlea responses to click trains, ramps, and steps in both directions. The transition time function of adaptation to constant click trains does not depend on click strength, but rather on click interval. On the background of steady state adaptation, click steps produce only transient changes of the adaptive state, opposite to step direction. Compared to constant train stimulation, adaptation is enhanced by descending click ramps, and diminished or reversed (near threshold) by ascending ramps.

Acoustic Stimulation↗
PubMed2006

Locating the initial stages of speech-sound processing in human temporal cortex.

It is commonly assumed that, in the cochlea and the brainstem, the auditory system processes speech sounds without differentiating them from any other sounds. At some stage, however, it must treat speech sounds and nonspeech sounds differently, since we perceive them as different. The purpose of this study was to delimit the first location in the auditory pathway that makes this distinction using functional MRI, by identifying regions that are differentially sensitive to the internal structure of speech sounds as opposed to closely matched control sounds. We analyzed data from nine right-handed volunteers who were scanned while listening to natural and synthetic vowels, or to nonspeech stimuli matched to the vowel sounds in terms of their long-term energy and both their spectral and temporal profiles. The vowels produced more activation than nonspeech sounds in a bilateral region of the superior temporal sulcus, lateral and inferior to regions of auditory cortex that were activated by both vowels and nonspeech stimuli. The results suggest that the perception of vowel sounds is compatible with a hierarchical model of primate auditory processing in which early cortical stages of processing respond indiscriminately to speech and nonspeech sounds, and only higher regions, beyond anatomically defined auditory cortex, show selectivity for speech sounds.

Adult↗
PubMed2004

Speech intelligibility of the callsign acquisition test in a quiet environment.

This paper reports on preliminary experiments aimed at standardizing speech intelligibility of military Callsign Acquisition Test (CAT) using average power levels of callsign items measured by the Root Mean Square (RMS) and maximum power levels of callsign items (Peak). The results obtained indicate that at a minimum sound pressure level (SPL) of 10.57 dBHL, the CAT tests were more difficult than NU-6 (Northwestern University, Auditory Test No. 6) and CID-W22 (Central Institute for the Deaf, Test W-22). At the maximum SPL values, the CAT tests reveal more intelligibility than NU-6 and CID-W22. The CAT-Peak test attained 95% intelligibility as NU-6 at 27.5 dBHL, and with CID-W22, 92.4% intelligibility at 27 dBHL. The CAT-RMS achieved 90% intelligibility when compared with NU-6, and 87% intelligibility score when compared with CID-W22; all at 24 dBHL.

Adolescent↗
PubMed1999

Hemispheric differences in processing tone frequency and amplitude modulations.

Transient frequency and amplitude modulations (FMs, AMs) of sound are requisite to speech recognition. We recorded whole-head magnetoencephalographic signals from seven subjects to binaural 620 ms 667 Hz tones, with 3, 30, or 300 ms FMs or AMs in the beginning or middle of the tone. Responses were significantly larger and earlier for FMs than AMs, for rapid than slow modulations, and for modulations at the beginning (BEG) than in the middle (MID) of the sound. BEG 3 ms FMs elicited strongest signals in the left and MID 3 ms FMs in the right hemisphere. Fast MID modulations produced significantly stronger responses in the right than left hemisphere. These differences may reflect different functions of the left and right hemisphere in speech perception.

Adult↗
PubMed2006

Perception of acoustic scale and size in musical instrument sounds.

There is size information in natural sounds. For example, as humans grow in height, their vocal tracts increase in length, producing a predictable decrease in the formant frequencies of speech sounds. Recent studies have shown that listeners can make fine discriminations about which of two speakers has the longer vocal tract, supporting the view that the auditory system discriminates changes on the acoustic-scale dimension. Listeners can also recognize vowels scaled well beyond the range of vocal tracts normally experienced, indicating that perception is robust to changes in acoustic scale. This paper reports two perceptual experiments designed to extend research on acoustic scale and size perception to the domain of musical sounds: The first study shows that listeners can discriminate the scale of musical instrument sounds reliably, although not quite as well as for voices. The second experiment shows that listeners can recognize the family of an instrument sound which has been modified in pitch and scale beyond the range of normal experience. We conclude that processing of acoustic scale in music perception is very similar to processing of acoustic scale in speech perception.

Acoustic Stimulation↗
PubMed1986

Simulation of mechanical to neural transduction in the auditory receptor.

A probabilistic model is described for transmitter release from hair cells, auditory neuron EPSP's, and discharge patterns. The model assumes that the release fraction of the transmitter is a function of stimulus intensity. It further assumes that some of this transmitter substance is taken back into the cell while some is irretrievably lost from the cleft. These assumptions differ from other recent models which propose multiple release sites, fixed release fractions, and no transmitter reuptake. The model produces realistic mammalian rate intensity functions, interval and period histograms, incremental responses, and adaptation effects. It mimics successfully the adaptation of successive EPSP amplitudes of the afferent neuron of the goldfish sacculus and offers a reinterpretation of the implications of these studies for hair cell synaptic mechanism.

Animals↗
PubMed2005

Auditory electrical tinnitus suppression in patients with and without implants.

The aim of this study was to evaluate the effectiveness of electrical tinnitus suppression in two groups of chronic severe tinnitus sufferers. Through standard tinnitus questionnaires, we compared the effectiveness of extratympanic and intratympanic auditory electrical stimulation (AES) by cochlear implants (CI) for the suppression or abolition of the perception of tinnitus and the decrease of its associated complaints. We made otolaryngological and comprehensive audiological assessment and also tinnitus measurement in each group of patients before and after AES and 50 days later. We investigated the dimensions of psychological complaints due to chronic and disabling tinnitus by means of the tinnitus questionnaire (TQ). The control examination during at least seven sessions (50 days) after AES in the group of patients without implants showed improvement in 20 of 32 patients (62.5%); 12 (37.5%) did not notice any change. In the comparative group of patients with implants, improvement occurred in 16 of 20 patients (75%); during the switch-on of the speech processor, these patients reported significant attenuation or complete suppression of their tinnitus. Complete suppression of the tinnitus after CI was observed for 11 patients (55%), and 5 patients (25%) demonstrated significant attenuation of tinnitus. Nonsuppression of tinnitus was observed for only 4 patients (25%). None of our patients was affected by an increment in the tinnitus owing to CI. The differences of means of scores in the standard TQ were significant in both groups of patients. A comparison of TQ score differences between patients with and without implants showed no significance. We concluded that AES is a useful and effective therapeutic intervention in patients with tinnitus. Extratympanic AES reduces the effects of the tinnitus but presents limitations, mainly owing to the short duration of the electrical residual inhibition of the tinnitus. CI is shown to be more efficient for the treatment of tinnitus, mainly because the electrical stimulation affects a wider area of the cochlea and is presented for longer sessions. Therefore, patients affected by incapacitating tinnitus should be considered for continuous use of electrical stimulation.

Adolescent↗
PubMedDate not supplied

[Habituation of auditory evoked potentials and emotional state].

"Fast" and "slow" habituation of N1 and N1-P2 components of auditory evoked potentials was studied in healthy subjects and in depressed patients. In patients, initially more low amplitudes of N1 and N1-P2 were revealed, as well as slowing down of habituation in the beginning of stimuli series and acceleration to its end (in healthy people--the greatest habituation in the initial part of the series and amplitude increase at its end), the absence of power effect in the component N1 at reaching, in the process of habituation, of the same minimum parameters as in healthy subjects. This points to weakening of dishabituation process parallel with well expressed "slow" habituation in patients and allows to suggest at expressed negative emotions a deficit of attention processes as a result of "internal abstraction".

Adolescent↗
PubMed1982

Auditory brainstem responses and masking level differences from persons with brainstem lesion.

Twenty subjects with abnormal auditory brainstem responses (ABR) and diagnosed brainstem lesion or disease were studied. Normal listeners were used as controls. The objective of the project was to examine the relationship of the particular ABR patterns exhibited by these subjects to the binaural masking level differences (MLD) and transbrainstem acoustic reflex (AR) patterns yielded by the same subjects. Patients whose ABR abnormalities commenced with brainstem potentials I, II, or III had small or no MLD and absent or abnormal AR. Patients whose ABR abnormalities commenced with brainstem potentials IV or V yielded normal MLD and AR behavior. Most important, these findings suggest that MLD size is influenced by activity which also contributes importantly to the development of the early auditory brainstem potentials.

Adult↗
PubMed1982

[Time resolution ability of the ear in presbycusis and sensorineural hearing disorders].

In psychoacoustical and electrophysiological experiments the time resolution ability in monaural and binaural hearing was investigated for defined signal parameters. The binaural stimulation is characterized by signals of different structure (dichotic stimulation). With regard to different functional changes in the peripheral and central areas of the hearing organ caused by presbycusis, these investigations confirm that there are similar changes in time resolution processes which may influence speech discrimination in presbycusis to a high degree. In patients with sensorineural hearing loss time resolution ability was reduced only slightly. No defined correlation between lack of time resolution ability and type or degree of hearing loss could be established.

Adult↗
PubMed1987

The Hitselberger sign as a perception phenomenon.

In the Hitselberger test the patient has to estimate the magnitude of the tactile part of a compound audio-tactile stimulus. From this point of view it is doubtful, that the sign is a simple peripheral phenomenon based on the impairment of the facial nerve by tumor pressure. To investigate the process of audiotactile perception we developed a device which delivers a calibrated compound audio-tactile stimulus. In the tested 70 patients with different sensorineural lesions there was no significant difference between the percentage values of positive Hitselberger signs in the various diagnostic groups. Evaluation of the different factors influencing the Hitselberger test results in a new concept of audiotactile perception.

Acoustic Stimulation↗
PubMed1988

Audiological evaluation of nonalcoholic, drug-free posttraumatic stress disorder patients.

Auditory functions of 32 Israeli soldiers with posttraumatic stress disorder (PTSD) were evaluated and compared with those of 32 matched controls without PTSD. The evaluation included peripheral auditory functions, tolerance to noise, and central auditory informational functions. Tolerance of intense auditory stimuli by PTSD patients was similar to that of controls. Significant differences were found between left and right ear central auditory functions in a subgroup of 13 PTSD subjects, but neither in other PTSD patients nor in controls. These findings are discussed in the light of previous research concerning abnormal responses to auditory stimulus in PTSD, hemispheric disconnection, alexithymia, and psychosomatic disorders.

Adult↗
PubMed2004

Transient brain responses predict the temporal dynamics of sound detection in humans.

The neural events leading up to the conscious experience of stimulus events have remained elusive. Here we describe stimulation conditions under which activation in human auditory cortex can be used to predict the temporal dynamics of behavioral sound detection. Subjects were presented with auditory stimuli whose energy smoothly increased from a silent to a clearly audible level over either 1, 1.5, or 2 s. Magnetoencephalographic (MEG) recordings were carried out in the passive and active recording conditions. In the active condition, the subjects were instructed to attend to the auditory stimuli and to press a response key when these became audible. In both conditions, the stimuli elicited a prominent transient response whose emergence is unexplainable by changes in stimulus intensity alone. This transient response was larger in amplitude over the right hemisphere and in the active condition. Importantly, behavioral sound detection followed this brain activation with a constant delay of 180 ms, and further the latency variations of the brain response were directly carried over to behavioral reaction times. Thus, noninvasively measured transient events in the human auditory cortex can be used to predict accurately the temporal course of sound detection and may therefore turn out to be useful in clinical settings.

Adult↗
PubMed2004

Interference and enhancement effects on interaural time discrimination and level discrimination in listeners with normal hearing and those with hearing loss.

It is known that many listeners with sensorineural hearing loss (SNHL) have difficulty performing binaural tasks. In this study, interference and enhancement effects on interaural time discrimination and level discrimination were investigated in 4 listeners with normal hearing (NH) and 7 listeners with SNHL. Just-noticeable differences were measured using 1/3-octave narrowband noises centered at 0.5 and 4 kHz. Noises were presented in isolation and together at equivalent sound pressure level (EqSPL) and equivalent sensation level (EqSL). Each noise served as target and distractor in the dual-band conditions. Congruent conditions included interaural differences in both noises that varied together, and incongruent conditions included an interaural difference in one noise with the second noise diotic. No significant enhancement effects were observed for either group in either task. Interference effects for the NH group were limited to the interaural level discrimination task in the 0.5-kHz target and 4-kHz distractor condition. Performance of participants with SNHL was similar to that of the NH group for interaural time discrimination with noises at EqSL but not EqSPL. In interaural level discrimination, listeners with SNHL demonstrated interference with a 4-kHz target and 0.5-kHz distractor. Results indicated that the relative levels of low- and high-frequency targets and distractors could affect binaural performance of individuals with SNHL but that in some conditions listeners with SNHL performed similarly to those with normal hearing. Implications of these results for binaural clinical tests and hearing aid fitting strategies are discussed.

Adult↗
PubMedDate not supplied

Threshold prediction from the auditory 40-Hz evoked potential.

This is an investigation of the accuracy with which the 40-Hz evoked potential (EP) threshold can be used to predict low frequency behavioral audiometric thresholds. The EP thresholds for 500 and 1000 Hz tone bursts were compared with behavioral thresholds obtained from 40 hearing-impaired ears. Correlation coefficients (between EP and behavioral thresholds) of 0.79 and 0.87 were obtained for the 500 and 1000 Hz signals, respectively. Confidence intervals for EP estimates of behavioral thresholds were -10 to +30 dB for 500 Hz signals and -20 to +20 for 1000 Hz. Problems associated with the use of the EP for predicting behavioral thresholds are discussed.

Adolescent↗
PubMed2006

The role of intensity upon pitch perception in cochlear implant recipients.

OBJECTIVES: Pitch plays a key role in the perception of speech and music, the recognition of a speaker's voice, and in analyzing complex auditory patterns. To date, little consideration has been given to the influence of stimulation level on pitch perception. The aim of this study was to investigate the impact of a sound's intensity on pitch perception in cochlear implant recipients using monopolar stimulation. STUDY DESIGN: Thirteen patients with an average implant use of 4.13 years took part in this study. All patients were implanted with MedEl Combi 40/40+ cochlear implants. METHODS: In the first part of the study, we performed a pitch ranking procedure to confirm that all patients were able to judge pitch changes. Using a visual scale, study participants were then asked to compare the pitch of an intensity-constant reference tone with the pitch of a test tone of varying intensity. RESULTS: Eleven (85%) patients were found to perceive a clear change in pitch with changing stimulus intensity. Statistical analysis showed a strong positive correlation in 10 patients (correlation coefficients between 0.99 and 0.71) and a strong negative correlation in 1 patient (r = -0.92). CONCLUSIONS: The results suggest that a distinct relationship exists between pitch perception and intensity of the stimulus. To date, speech coding strategies do not support these findings. Nevertheless, we believe that for the optimized most natural perception of sounds, especially music, the described particularities of pitch perception need to be respected, and further investigations on this topic are necessary.

Acoustic Stimulation↗