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At least 145 records · Page 8Linked to original sources
PubMed2002

Axonal injury in auditory nerve observed in reversible latency changes of brainstem auditory evoked potentials (BAEP) during cerebellopontine angle manipulations in rats.

Intraoperative monitoring of brainstem auditory evoked potentials (BAEP) has been widely utilized to reduce the incidence of postoperative hearing disturbance due to cerebellopontine angle manipulations. The prolongation of wave V of BAEP is usually used as a criterion to warn the surgeons to modify their surgical maneuvers. However, it is not known whether all neuropathological changes are avoided if BAEP latency intraoperatively returns to the baseline level or some neuropathological changes 'silently' occur even if BAEP normalizes. The aim of this study was to experimentally clarify this point that would be important for the long-term prognosis of patients' hearing. The cerebellopontine angle portion of the auditory nerve was quantitatively compressed in the rats and reversible prolongation of BAEP latency was reproduced just as it occurs during surgery in humans. Twenty-four hours after the compression, the auditory nerve was removed for beta-APP immunostaining to investigate the degree of axonal injury. The results of the present study disclosed that axonal injury occurred even in the cases where the intraoperative normalization of prolonged wave IV (equivalent to wave V in humans) latency had been obtained. Therefore, the interpretation of BAEP changes based only on the prolongation of the latency of BAEP was not enough to prevent the auditory nerve from developing morphological changes. Changes in the amplitude of wave V of BAEP appears to be more sensitive than its latency change as an intraoperative indicator for axonal injury in the auditory nerve.

Amyloid beta-Protein Precursor↗
PubMed1999

The N100 auditory cortical evoked potential indexes scanning of auditory short-term memory.

OBJECTIVE: To study activity of auditory cortex reflected by the N100 and P200 components of the auditory evoked potentials during memorization and scanning of short-term memory stores. METHODS: In a MEMORY task subjects classified a probe digit either as a member or not a member of a previously presented list of digits that varied in size from one, 3, 5 and 7 items. For comparison, subjects in a NUMBER task listened to a list of digits as in the MEMORY task but determined only whether the probe digit as odd or even. Evoked potentials to the presentation list and to probes were recorded from scalp electrodes and separately averaged for both tasks. The components peaking at approximately 100 ms (N100) and 200 ms (P200) that reflect activity of primary auditory cortex were identified and peak amplitudes and latencies were measured. RESULTS: For presentation set items, the amplitude of N100 was affected by set size in the MEMORY but not in the NUMBER task; N100 was larger for the one item set than for the 3, 5, and 7 item sets. P200 increased in amplitude in a linear manner for both the MEMORY and NUMBER tasks. For probe items, N100 but not P200 amplitude decreased in a linear manner as the number of items in the presentation set increased in the MEMORY but not in the NUMBER task. The linear change of N100 amplitude during memory scanning was particular to inset but not to out-of-set probes. The amplitudes of both N100 and P200 were almost twice as large in probe digits than in the digits in the presentation set in both the MEMORY and NUMBER tasks. CONCLUSION: Auditory sensory cortical activity in humans during an auditory short-term memory task shows dynamic changes during both memorization and memory scanning.

Acoustic Stimulation↗
PubMed1994

Effects of auditory and visual interference on auditory-visual delayed matching to sample in monkeys (Macaca fascicularis).

Two monkeys were trained on an auditory-visual (AV) delayed matching-to-sample (DMS) task with auditory cues serving as sample stimuli and visual cues serving as comparison stimuli. To determine whether the monkeys were remembering auditory or visual information during the delay period, auditory and visual interference were presented following the sample stimulus. Auditory interference had little effect on AV DMS performance. In contrast, visual interference severely impaired AV DMS performance, indicating that the monkeys were remembering visual information during the delay period. This finding may reflect a predisposition of monkeys toward remembering information via their dominant visual modality.

Animals↗
PubMed2000

Behavioral auditory assessment of young infants: methodological limitations or natural lack of auditory responsiveness?

The determination of auditory thresholds by means of behavioral techniques in young infants can be difficult. This could be the result of limitations in methodology, a lack of observable auditory responsiveness, or both. In the current study, 2- and 4-month old infants were tested under enhanced conditions for obtaining behavioral responses (i.e., salient auditory stimuli, reduced visual distractions, reinforced correct responses). A two-interval, forced-choice task with four intensity levels was used. Although a behavioral threshold was obtained for the 4-month-olds, threshold determination for the 2-month-olds remained elusive. In light of the current findings and previous studies of visual acuity of infants, these results suggest a lack of behavioral responsiveness to auditory stimuli for the younger infants rather than methodological limitations. With infants in the 2-month-old age range, clinical audiologists should expect few behavioral responses to auditory stimuli at intensity levels below those that elicit startle responses.

Attention↗
PubMed1997

Auditory evoked potential index: a quantitative measure of changes in auditory evoked potentials during general anaesthesia.

We describe a novel index derived from the auditory evoked potential, the auditory evoked potential index, and we compare it with latencies and amplitudes related to clinical signs of consciousness and unconsciousness. Eleven patients, scheduled for total knee replacement under spinal anaesthesia, completed the study. The initial mean (SD) value of the auditory evoked potential index was 72.5 (11.2). During the first period of unconsciousness it decreased to 39.6 (6.9) and returned to 66.8 (12.5) when patients regained consciousness. Thereafter, similar values were obtained whenever patients lost and regained consciousness. Latencies and amplitudes changed in a similar fashion. From all parameters studied, Na latencies had the greatest overlap between successive awake and asleep states. The auditory evoked potential index and Nb latencies had no overlap. The consistent changes demonstrated suggest that the auditory evoked potential index could be used as a reliable indicator of potential awareness during propofol anaesthesia instead of latencies and amplitudes.

Anesthesia, General↗
PubMed2005

Opposite effects of tetanic stimulation of the auditory thalamus or auditory cortex on the acoustic startle reflex in awake rats.

The amygdala mediates both emotional learning and fear potentiation of startle. The lateral amygdala nucleus (LA) receives auditory inputs from both the auditory thalamus (medial geniculate nucleus; MGN) and auditory association cortex (AAC), and is critical for auditory fear conditioning. The central amygdala nucleus, which has intra-amygdaloid connections with LA, enhances startle magnitude via midbrain connections to the startle circuits. Tetanic stimulation of either MGN or AAC in vitro or in vivo can induce long-term potentiation in LA. In the present study, behavioural consequences of tetanization of these auditory afferents were investigated in awake rats. The acoustic startle reflex of rats was enhanced by tetanic stimulation of MGN, but suppressed by that of AAC. All the tetanization-induced changes of startle diminished within 24 h. Blockade of GABAB receptors in the LA area reversed the suppressive effect of tetanic stimulation of AAC on startle but did not change the enhancing effect of tetanic stimulation of MGN. Moreover, transient electrical stimulation of MGN enhanced the acoustic startle reflex when it lagged behind acoustic stimulation, but inhibited the acoustic startle reflex when it preceded acoustic stimulation. The results of the present study indicate that MGN and AAC afferents to LA play different roles in emotional modulation of startle, and AAC afferents are more influenced by inhibitory GABAB transmission in LA.

Acoustic Stimulation↗
PubMed2006

Posttraining lesions of the auditory thalamus, but not cortex, disrupt the inhibition of fear conditioned to an auditory stimulus.

The purpose of this study was to examine the effects of lesions within the auditory system in an effort to disrupt the processing of the noise stimulus conditioned to inhibit fear. To accomplish this, three experiments were conducted in which rats were first given feature-negative discrimination training in which a noise was conditioned to inhibit fear to a light that signals danger. Following training, rats were given lesions of the medial geniculate body (MGB), auditory thalamus (ADT), or auditory cortex (CTX). Next, rats were tested for the ability to inhibit fear in the presence of the noise safety signal. The results of these experiments indicated that bilateral lesions of ADT disrupted the ability of the noise inhibitor to inhibit fear. In contrast, lesions largely restricted to the MGB or CTX did not disrupt the inhibition of fear. Along with past studies, these results suggest that an auditory pathway(s), which includes projections from the tectum to the ADT, is used to detect the safety properties previously conditioned to an auditory stimulus.

Acoustic Stimulation↗
PubMed1994

Processing of auditory stimuli during auditory and visual attention as revealed by event-related potentials.

Auditory event-related brain potentials (ERPs) were recorded during auditory and visual selective attention tasks. Auditory stimuli consisted of frequent standard tones (1000 Hz) and infrequent deviant tones (1050 Hz and 1300 Hz) delivered randomly to the left and right ears. Visual stimuli were vertical line gratings randomly presented on a video monitor at mean intervals of 6 s. During auditory attention, the subject attended to the stimuli in a designated ear and responded to the 1300-Hz deviants occurring among the attended tones. During visual attention, the subject responded to the occasional visual stimuli. ERPs for tones delivered to the attended ear were negatively displaced relative to ERPs elicited by tones delivered to the unattended ear and to ERPs elicited by auditory stimuli during visual attention. This attention effect consisted of negative difference waves with early and late components. Mismatch negativities (MMNs) were elicited by 1300-Hz and 1050-Hz deviants irrespective of whether they occurred among attended or unattended tones. MMN amplitudes were unaffected by attention, supporting the proposal that the MMN is generated by an automatic cerebral discrimination process.

Adult↗
PubMed1991

A composite model of the auditory periphery for the processing of speech based on the filter response functions of single auditory-nerve fibers.

A composite model of the auditory periphery, based upon a unique analysis technique for deriving filter response characteristics from cat auditory-nerve fibers, is presented. The model is distinctive in its ability to capture a significant broadening of auditory-nerve fiber frequency selectivity as a function of increasing sound-pressure level within a computationally tractable time-invariant structure. The output of the model shows the tonotopic distribution of synchrony activity of single fibers in response to the steady-state vowel [e] presented over a 40-dB range of sound-pressure levels and is compared with the population-response data of Young and Sachs (1979). The model, while limited by its time invariance, accurately captures most of the place-synchrony response patterns reported by the Johns Hopkins group. In both the physiology and in the model, auditory-nerve fibers spanning a broad tonotopic range synchronize to the first formant (F1), with the proportion of units phase-locked to F1 increasing appreciably at moderate to high sound-pressure levels. A smaller proportion of fibers maintain phase locking to the second and third formants across the same intensity range. At sound-pressure levels of 60 dB and above, the vast majority of fibers with characteristic frequencies greater than 3 kHz synchronize to F1 (512 Hz), rather than to frequencies in the most sensitive portion of their response range. On the basis of these response patterns it is suggested that neural synchrony is the dominant auditory-nerve representation of formant information under "normal" listening conditions in which speech signals occur across a wide range of intensities and against a background of unpredictable and frequently intense acoustic interference.

Animals↗
PubMed1983

Early auditory experience aligns the auditory map of space in the optic tectum of the barn owl.

Auditory and visual space are mapped in the optic tectum of the barn owl. Normally, these maps of space are in close mutual alignment. Ear plugs inserted unilaterally in young barn owls disrupted the binaural cues that constitute the basis of the auditory map. Yet when recordings were made from the tecta of these birds as adults, the auditory and visual maps were in register. When the ear plugs were removed from these adult birds and binaural balance was restored, the auditory maps were shifted substantially relative to the visual maps and relative to the physical borders of the tecta. These results demonstrate that the neural connectivity that gives rise to the auditory map of space in the optic tectum can be modified by experience in such a way that spatial alignment between sensory modalities is maintained.

Acoustic Stimulation↗
PubMed2006

Cortical response to auditory motion suggests an asymmetry in the reliance on inter-hemispheric connections between the left and right auditory cortices.

The aim of the current study was to measure the brain's response to auditory motion using electroencephalography (EEG) to gain insight into the mechanisms by which hemispheric lateralization for auditory spatial processing is established in the human brain. The onset of left- or rightward motion in an otherwise continuous sound was found to elicit a large response, which appeared to arise from higher-level nonprimary auditory areas. This motion onset response was strongly lateralized to the hemisphere contralateral to the direction of motion. The response latencies suggest that the ipsilateral response to the leftward motion was produced by indirect callosal projections from the opposite hemisphere, whereas the ipsilateral response to the rightward motion seemed to receive contributions from direct thalamocortical projections. These results suggest an asymmetry in the reliance on inter-hemispheric projections between the left and right auditory cortices for auditory spatial processing.

Acoustic Stimulation↗
PubMed2000

Functional anatomy of auditory verbal imagery in schizophrenic patients with auditory hallucinations.

OBJECTIVE: This study investigated the functional neuroanatomy of inner speech and auditory verbal imagery in schizophrenic patients predisposed to auditory hallucinations. METHOD: Eight patients with schizophrenia with a history of prominent auditory hallucinations and six comparison subjects underwent functional magnetic resonance imaging while generating inner speech or imagining external speech. RESULTS: Patients showed no differences while generating inner speech but experienced a relatively attenuated response in the posterior cerebellar cortex, hippocampi, and lenticular nuclei bilaterally and the right thalamus, middle and superior temporal cortex, and left nucleus accumbens during auditory verbal imagery. CONCLUSIONS: Patients with schizophrenia who were prone to auditory hallucinations show attenuated activation when processing inner speech in areas implicated in verbal self-monitoring.

Adult↗
PubMed2002

Electrical stimulation of the auditory nerve via cochlear implants in patients with auditory neuropathy.

Auditory neuropathy (AN) is a term used to describe an auditory disorder in which there is evidence of normal outer hair cell function (otoacoustic emissions and/or cochlear microphonics) and poor function of the auditory nerve (absent or highly distorted auditory brain stem response starting with wave I). Many of these patients have evidence of generalized peripheral nerve disease, leading to an assumption that the peripheral portion of the auditory nerve is the most likely site of lesion. A small group of these patients has received cochlear implants, and the majority of them achieve average to above-average performance. Although this outcome may seem incongruous with neural disease, average performance by patients with AN may be a result of the reintroduction of neural synchrony by electrical stimulation and/or the fact that most deaf patients have poor nerve survival. Although cochlear implants are promising for deaf patients with AN, more study of the disorder is needed.

Adult↗
PubMed2004

Elevated pitch perception owing to carbamazepine-activating effect on the peripheral auditory system: auditory brainstem response study.

Auditory disturbance is an uncommon side effect of carbamazepine, the pathophysiologic mechanism of which has not been clearly elucidated. We performed an auditory brainstem response study in a 9-year-old boy with epilepsy who had suffered from falsely higher pitch perception immediately after the start of carbamazepine treatment. The auditory brainstem response results showed that both the peak latency of wave V and the interpeak latencies of waves I to V were significantly prolonged with 85 dB HL click stimulation and that the peak amplitudes of the waves were noticeably elevated, particularly with lower click stimulation intensity. Although it has been shown that carbamazepine has a suppressive effect on the central nervous system, these auditory brainstem response findings might constitute evidence of a carbamazepine-activating effect on the peripheral auditory system, which probably increased the sensitivity to low-pitched sounds, causing the development of falsely higher pitch perception in our patient.

Anticonvulsants↗
PubMed1996

Auditory nerve disease of both ears revealed by auditory brainstem responses, electrocochleography and otoacoustic emissions.

We report on two patients who showed absence of auditory brainstem response (ABR) but broad compound action potentials on electrocochleograms and almost normal otoacoustic emissions, together with absence of caloric response and preservation of per rotatory nystagmus for both ears. Patient 1, a 53-year-old woman, had noted auditory and vestibular problems since the age of 15 years, and Patient 2, a 68-year-old woman, had noted problems of the same age of 30 years. They could hear words and understand sentences if spoken slowly, but they could not discriminate monosyllables very well. Their auditory examinations disclosed mild threshold elevation in pure-tone audiometry and markedly poor scores in speech audiometry and good scores in auditory comprehension test. They were diagnosed as having auditory nerve disease of unknown cause.

Acoustic Stimulation↗
PubMed2002

Auditory dominance in temporal processing: new evidence from synchronization with simultaneous visual and auditory sequences.

Evidence that audition dominates vision in temporal processing has come from perceptual judgment tasks. This study shows that this auditory dominance extends to the largely subconscious processes involved in sensorimotor coordination. Participants tapped their finger in synchrony with auditory and visual sequences containing an event onset shift (EOS), expected to elicit an involuntary phase correction response (PCR), and also tried to detect the EOS. Sequences were presented in unimodal and bimodal conditions, including one in which auditory and visual EOSs of opposite sign coincided. Unimodal results showed greater variability of taps, smaller PCRs, and poorer EOS detection in vision than in audition. In bimodal conditions, variability of taps was similar to that for unimodal auditory sequences, and PCRs depended more on auditory than on visual information, even though attention was always focused on the visual sequences.

Analysis of Variance↗
PubMedDate not supplied

[Communication and auditory behavior obtained by auditory evoked potentials in mammals, birds, amphibians, and reptiles].

METHODS ANIMALS: amphibians, Frog catesbiana (frog bull, 30 animals); reptiles, Sceloporus torcuatus (common small lizard, 22 animals); birds: Columba livia (common dove, 20 animals), and mammals, Cavia porcellus, (guinea pig, 20 animals). With regard to lodging, all animals were maintained at the Institute of Human Communication Disorders, were fed with special food for each species, and had water available ad libitum. Regarding procedure, for carrying out analysis of auditory evoked potentials of brain stem SPL amphibians, birds, and mammals were anesthetized with ketamine 20, 25, and 50 mg/kg, by injection. Reptiles were anesthetized by freezing (6 degrees C). Study subjects had needle electrodes placed in an imaginary line on the half sagittal line between both ears and eyes, behind right ear, and behind left ear. Stimulation was carried out inside a no noise site by means of a horn in free field. The sign was filtered at between 100 and 3,000 Hz and analyzed in a computer for provoked potentials (Racia APE 78). RESULTS: In data shown by amphibians, wave-evoked responses showed greater latency than those of the other species. In reptiles, latency was observed as reduced in comparison with amphibians. In the case of birds, lesser latency values were observed, while in the case of guinea pigs latencies were greater than those of doves but they were stimulated by 10 dB, which demonstrated best auditory threshold in the four studied species. Last, it was corroborated that as the auditory threshold of each species it descends conforms to it advances in the phylogenetic scale. CONCLUSIONS: Beginning with these registrations, we care able to say that response for evoked brain stem potential showed to be more complex and lesser values of absolute latency as we advance along the phylogenetic scale; thus, the opposing auditory threshold is better agreement with regard to the phylogenetic scale among studied species. These data indicated to us that seeking of auditory information is more complex in more evolved species.

Amphibians↗
PubMed2006

[Auditory capability evaluation for children after cochlear implantation using meaningful auditory integration scale].

OBJECTIVE: To analyze the auditory capability of preschool children before and after cochlear implantation using meaningful auditory integration scale (MAIS) questionnaire. METHODS: Eighty-two prelingually deaf patients participated in this study. They received a cochlear implant at the age of 3 to 6 years and 11 months. The audiologists who were trained for the research used the MAIS questionnaire. Audiologists asked for the parents' answers and recorded all the information about the device using (Q1,2) and the patient's spontaneous auditory behavioural responses including spontaneous alerting to sound Q3 approximately 6 and deriving meaning from sound (Q7 approximately 10). The evaluation was performed before operation and 1 , 3, 6 months, 1, 1.5, 2 years after switch-on. RESULTS: The scores of question 1a and 1b were not significantly different among the different periods after switch-on. The scores of question 2 to 10 were significantly different among the different periods after switch-on. CONCLUSIONS: Considerable variability across subjects' auditory ability after cochlear implantation was noted. Most of the patients showed no consistent response to sound in everyday life before implantation. After cochlear implantation, a significant increase in auditory capability occurred. The children demonstrated faster development of device using relative to spontaneous alerting to sound and deriving meaning from sound.

Auditory Perception↗