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At least 1,315 records · Page 73Linked to original sources
PubMed1995

Auditory brainstem response findings in brainstem ischemia following selective occlusion of the anterior inferior cerebellar artery in the rat.

Auditory brainstem responses (ABRs) were measured ipsilaterally (n = 13) or contralaterally (n = 5) after inducing permanent right and left anterior inferior cerebellar artery (AICA) occlusion. Three types of wave patterns were classified when ABRs were recorded ipsilaterally. In type 1 (n = 4) all components disappeared; in type 2 (n = 2) all components disappeared transiently and then reappeared; and in type 3 (n = 7) only the latency difference between components I and IV increased. These findings indicate that all components reappeared in type 2 responses because cochlear blood flow was re-established quickly by collateral circulation, while type 3 changes reflected the relative sensitivity of the cochlea to ischemic damage when compared with the rest of the auditory pathways. When the ABRs were recorded contralaterally, characteristic findings included a delay in latency of component IV and a significant increase in inter-peak latency in components I-IV and IIb-IV.

Animals↗
PubMed1978

Vestibulothalamic projections in man--a sixth primary sensory pathway.

1. Responses suggesting activation of the vestibular system, elicited by electrical stimulation of the human thalamus during 22 routine stereotaxic neurosurgical procedures, were examined in a retrospective study to determine the possible existence of vestibulothalamo-cortical projections in man. 2. Such responses were most frequently described as sensations of movement through space and were associated with two distinct vestibulothalamic projections: a) an anterior relay was situated ventral to the medial lemniscus, passing lateral to the red nucleus and dorsal to the subthalamic nucleus prior to terminating in the nucleus ventrointermedius (Vim) (comparable to VPLo in primates); b) a posterior relay associated with the auditory pathway (lateral lemniscus and brachium of the inferior colliculus) projected to the medial geniculate body. 3. The production of sensations of motion in conscious patients by stimulating areas that are similar to those reported constituting vestibulothalamic pathways in cats and primates implies a distinct primary sensory cortical projection for processing information from the vestibular receptors pertaining to the recognition of spatial movements.

Brain Mapping↗
PubMed1992

Influence of masker bandwidth on binaural masking level differences.

Masking level differences (MLDs) were investigated using masking noise with 160 Hz (amplitude-modulated noise) and 600 Hz (filtered-random noise) bandwidth. One hundred normally hearing subjects received the MLD test under both types of noise. Significant differences between noise types were observed in both N0S pi and N pi S0 conditions; MLDs were larger in amplitude-modulated noise. Consideration of these differences would indicate that older MLD norms based solely on filtered-random noise are invalid for amplitude-modulated noise especially where bandwidth differences in the noise exist. Were the norms for 600-Hz-wide filtered-random noise to be applied to results of MLD testing performed using 160-Hz-wide amplitude-modulated noise, patients with lesions in the central auditory pathway might exhibit normal or borderline normal results. Clinical MLD norms established on one type of noise should not be used to interpret MLD results obtained using a different type of noise.

Adolescent↗
PubMed1976

[Adaptational behaviour of peripheral and central acoustic responses in guinea pigs under the influence of various fractions of an extract from Gingko biloba (author's transl)].

Experimental studies on 114 guinea pigs proved definitely the influence of an extract from Ginkgo biloba batch no. 02 on the acoustic system. Experiments with animals ensured that the adaptation of excitation of the organ of Corti is significantly influenced. This result is shown by registrations of the acoustic nerve potentials in the adapted and nonadapted state. The relation of excitation to adaptation is significantly changed. Under adaptation of excitation an influence on the metabolism of involution is probable. The slow evoked potentials of the acoustic cortex showed no additional influence on the central auditory pathways. With the Ginkgo biloba extract it is probably possible to diminish sound damages caused by white noise. Further experiments on animals are necessary to ensure the application of this pharmaceutical preparation for clinical use.

Acoustic Stimulation↗
PubMed1985

Effect of bilirubin on brainstem auditory evoked potentials in the asphyxiated rat.

We measured brainstem auditory evoked responses (BAER) in four groups of paralyzed, ventilated, adult rats. Group A (n = 2) received intravenous albumin; group B (n = 5) received bilirubin in albumin; group C (n = 7) was asphyxiated and then received albumin; and group D (n = 19) was asphyxiated and received bilirubin in albumin. When compared with control values, no changes in BAER occurred in groups A or B and only slight changes were found in group C. In group D, seven rats died and seven suffered a marked secondary deterioration of the BAER following recovery, a phenomenon that did not occur in group C (p = 0.02). Bilirubin toxicity appears to be responsible for the changes in BAER but prior asphyxia was necessary for this effect to occur. Because the changes that occurred in group D involved all four major waves, it is not possible to separate out a toxic effect of bilirubin, localized to the auditory nerve and the auditory pathway, from a generalized systemic effect which could cause attenuation of the entire response. The BAER may be useful, however, as a noninvasive means of identifying bilirubin toxicity in the newborn.

Animals↗
PubMed1983

Studies on the temporary effect of noise on the auditory function in man.

ECoG and ABR recordings were performed on 22 young, normal-hearing persons, before and after exposure to fatiguing noise. Temporary Threshold Shift (TTS) of up to 35 dB at 4-6 kHz was induced by octave band noise with centre frequency at 2.8 kHz. The latency of waves I, III, V and ACAP (Auditory Compound Action Potential) and intervals between waves I-III, III-V, I-V and ACAP-V were analysed as functions of stimulus intensity in pre- and post-exposure recordings. In post-exposure recordings a threshold elevation, a significant increase of latency and unaltered intervals between the successive waves and ACAP were observed. It was concluded that the noise-induced auditory fatigue, measured as TTS, originates within the cochlea and is transferred to the auditory pathways. The great intersubject variability of the data obtained indicates that the TTS may be a useful measure of individual sensitivity to noise, but prognosis on the presumed Permanent Threshold Shifts (PTS) based on the evaluation of TTS would seem doubtful.

Auditory Fatigue↗
PubMed1992

[Auditory evoked potentials and tumor of the cerebellopontine angle].

The technique of auditory evoked potentials evaluates the auditory pathways along the vestibulocochlear nerve and in the brainstem. The authors stress the importance of this examination in the diagnosis of tumours of the cerebellopontine angle and they discuss its place in relation to radiological investigations.

Cerebellar Neoplasms↗
PubMed2003

Acute effects of cholecystokinin tetrapeptide on brain stem auditory evoked potentials in healthy volunteers.

This study investigated the effects of continuous slow intravenous infusion of cholecystokinin tetrapeptide (CCK-4) on brain stem auditory evoked potentials (BSAEP) in healthy subjects. Twenty-four subjects, 15 females and 9 males, were assigned to infusion with either placebo or CCK-4 in a randomized, double-blind, parallel group design. BSAEPs, mood, physical symptoms, and vital signs were assessed once before infusion and at 10 min and 40 min after the onset of infusion. In the 16 subjects (N = 8, CCK-4; N = 8, placebo) CCK-4, compared to placebo, delayed peak I latency during early infusion, slowed the latencies of peaks III and V, and decreased the amplitude of peak III throughout the infusion. No significant treatment differences were observed with respect to symptoms, mood, or cardiovascular measures. These preliminary findings suggest that CCK-4 may interfere with information processing in the brain stem auditory pathways and that prolonged intravenous CCK-4 administration may be a useful challenge paradigm for investigating CCK's modulatory role on brain stem mechanisms mediating anxiety and panic in humans.

Adolescent↗
PubMed1997

Synergestic effects of noise and aminoglycoside antibiotic (gentamicin) on auditory function in the gerbil.

Exposure to excessive noise can cause auditory impairment in people as well as in animals, which can be aggravated by many different ototoxic substances, such as aminoglycosides. In the present study, the gerbil was selected as the experimental animal because the gerbil has low-frequency auditory sensitivity that is similar to human beings. Auditory function in gerbils upon exposure to noise and/or gentamicin was evaluated from non-invasive records of brainstem auditory evoked potentials (BAEPs). Fifty mature male Mongolian gerbils were divided randomly into four groups. The control group was exposed neither to noise nor to gentamicin. The noise group was exposed to 100dBA noise ten hours a day for four weeks. The gentamicin group was treated with one dose of gentamicin, 75 mg/Kg i.m., daily for four weeks. The noise + gentamicin group was exposed concurrently to both noise and gentamicin treatment. BAEPs were recorded from all gerbils 24 hours before any experimental treatment, then every week for eight consecutive weeks. Long-term exposure to noise and/or gentamicin treatment was found to reduce gerbil's body weight. The increase in auditory threshold upon concurrent exposure to both noise and gentamicin treatment (evaluated from BAEPs) exceeded the sum of effects caused by exposure to noise alone and to gentamicin alone. Although differences of peak or interpeak latencies among the four groups were not statistically significant, large standard deviations were noted in the noise+gentamicin group. Thus the apparent threshold shifts in gerbils indicated a major noise and/or gentamicin induced auditory impairment to the cochlea, and the slight latency variations probably suggested a minor injury to the auditory pathways. We emphasize that noise and aminoglycoside antibiotic gentamicin can cause damage to the hearing ability at the frequency range vital to human speech recognition, and their effects are synergetic.

Animals↗
PubMed1998

Long-term degeneration in the cochlear nerve and cochlear nucleus of the adult chinchilla following acoustic overstimulation.

Adult chinchillas were exposed once to an octave-band noise, centered at 4 kHz, and allowed to survive for 16 days or for 1, 2, 4, and 8 months. Axonal degeneration was mapped in the cochlear nucleus, using the Nauta-Rasmussen silver method, and related to hair cell damage and to loss of myelinated nerve fibers in the osseous spiral lamina of the cochlea. Axonal degeneration in the dorsal cochlear nucleus had already reached a peak by 16 days and disappeared after 1 month. Meanwhile, myelinated nerve fiber degeneration in the cochlea extended basally, followed 2 weeks to 2 months later by spread of axonal degeneration into the corresponding high-frequency region of the ventral cochlear nucleus. Axonal degeneration occurred early in the low-frequency region of the ventral cochlear nucleus, followed 2-4 weeks later by spread of myelinated fiber degeneration into more apical regions of the cochlea. New degeneration of axons in the cochlear nerve and in the ventral cochlear nucleus continued to occur for up to 8 months after stimulation. These findings imply that plastic changes in the central auditory pathways could play a role in the long-term effects of cochlear damage and acoustic overstimulation, possibly leading to a chronic neurodegenerative condition in the ear and in the brain.

Acoustic Stimulation↗
PubMed1990

The effects of experimental brain-stem ischaemia on brain-stem auditory evoked potentials in primates.

We related intracranial auditory brain-stem evoked potentials (BAEPs) to the surface BAEP using a model of focal brain-stem ischaemia. In 17 baboons anaesthetised with alpha-chloralose, BAEPs were recorded bilaterally at the mastoids and in the caudal lateral lemniscus (LL) and inferior colliculus (IC), in response to monaural click stimulation. Electrodes at these sites were each connected to the positive input of a differential amplifier, and one other electrode, placed at the vertex, was connected to all the negative inputs. Measurements of local cerebral blood flow (CBF) by hydrogen clearance were made at the LL and IC sites. The LL wave form contained 5-7 positive peaks, the second (B wave) being dominant and coinciding with the negative wave II of the surface BAEP. Following graded ischaemia, produced by basilar artery occlusion and controlled hypotension, the latency changes of these two peaks were significantly correlated, as were those of the third wave (C wave) of the LL response and the surface wave III. In the IC, the contralateral wave form contained 4 positive waves (A-D) and a later, dominant, slow negative wave; changes in its peak latency and those of the slow negative surface wave were similarly correlated. The thresholds of local CBF for increases in latency of waves B and C in the LL were similar (12-15 ml/100 g/min), but in the IC the thresholds were 20, 30-35 and 20-24 ml/100 g/min for the B, C and slow negative waves, respectively. Our data indicate that a gradient of sensitivity to ischaemia is present along the brain-stem auditory pathways; this could explain the earlier change of the late, rather than early, BAEP components as reported in clinical cases involving brain-stem lesions.

Animals↗
PubMed1995

Changes in auditory P300 event-related potentials and brainstem evoked potentials in diabetes mellitus.

To investigate the influence of diabetes mellitus on higher cognitive functions electrophysiologically, we studied auditory P300 event-related potentials (P300) in 40 NIDDM patients, taking into account wave I-V latencies (I-V) in auditory brainstem evoked potentials, clinical parameters and head MRI findings. Compared with 20 controls, diabetics had significantly longer P300 and I-V latencies. P300 latencies in diabetics correlated with neither I-V, HbA1, blood glucose levels, nor disease duration. Of the 13 diabetics investigated neuroradiologically, four had lacunar infarcts with prolonged electrophysiological values. The remaining nine had normal MRI scans, but their physiological parameters were still significantly longer than those of controls. These findings suggest that NIDDM can independently alter higher cognitive and the central auditory pathway functions. Our data also suggest that these alterations occur regardless of the recent metabolic derangement and disease duration. Cerebrovascular ischemia, if present, also appears to contribute in part to cognitive alterations.

Acoustic Stimulation↗
PubMed1998

Strategies for hearing in noise: peripheral control over auditory sensitivity in the bushcricket sciarasaga quadrata (Austrosaginae: tettigoniidae)

The carrier frequency of the call of the Australian bushcricket Sciarasaga quadrata is unusually low for tettigoniids at 5 kHz. The sound transmission measured in the habitat of the insect reflects the advantages of producing low- rather than high-frequency signals; attenuation is explained almost entirely by the spherical spreading of sound. The natural vibration frequency of the wings is controlled by size and stiffness. The small tegmina are unusually fleshy, with an order-of-magnitude higher water content than in comparable sagine species. Reduced stiffness allows the insect to call at low carrier frequencies, albeit at lower intensity levels (60 dB SPL at 1 m), than bushcrickets of comparable size (80-90 dB SPL). The responses of the tympanic nerve and a first-order interneurone (omega neurone) in the afferent auditory pathway showed that the hearing system is most sensitive to frequencies of 15-20 kHz, an effective mismatch to the conspecific call resulting in a reduced sensitivity of approximately 20 dB at the carrier frequency of the call. S. quadrata can occlude its spiracular opening, which increases the sensitivity of the ear to lower frequencies. Under such conditions, the best frequency of the ear matched that of the carrier frequency of the call. We measured the activity of auditory neurones in the field, noting the ability of the open and partially closed ear to filter out potentially masking calls of congenerics. At the same time, the directionality of the system was only slightly reduced in the closed relative to the open spiracle status. We discuss the evolutionary advantages of an insect both calling with a low carrier frequency and having the ability to close down the tracheal system to avoid the effects of masking. In addition, we consider the advantages of such a signalling system in avoiding the most significant predator of the male, the ormine fly Homotrixa alleni.

Journal Article↗
PubMed2006

Sensorineural hearing loss in insulin-like growth factor I-null mice: a new model of human deafness.

It has been reported that mutations in the gene encoding human insulin-like growth factor-I (IGF-I) cause syndromic hearing loss. To study the precise role of IGF-I in auditory function and to hypothesize the possible morphological and electrophysiological changes that may occur in the human inner ear, we have analysed the auditory brainstem response in a mouse model of IGF-I deficiency. We show here that homozygous Igf-1(-/-) mice present an all-frequency involved bilateral sensorineural hearing loss. Igf-1(-/-) mice also present a delayed response to acoustic stimuli; this increases along the auditory pathway, indicating a contribution of the central nervous system to the hearing loss in Igf-1(-/-) mice. These results support the use of the Igf-1(-/-) mouse as a new model for the study of human syndromic deafness.

Acoustic Stimulation↗
PubMed1996

Brainstem auditory evoked potentials in respiratory insufficiency following encephalitis.

Brainstem auditory evoked potentials (BAEPs) were recorded in 14 artificially ventilated patients (12 males, 2 females; mean age 33.3 +/- 16.3 years, range 18-67) with respiratory insufficiency resulting from severe inflammatory encephalopathies. The results were compared with those of 17 healthy volunteers (13 males, 4 females; mean age 27.4 +/- 5.3 years, range 21-45). BAEPs in the study patients showed prolonged interpeak latencies (I-III, I-V, III-V, IV-V) and delayed absolute latencies of waves I, II, III, and V at least on one side. Because the auditory pathways are in the near vicinity of the respiratory control centers in the brainstem, the electrophysiologic abnormalities of wave III and the IV/V complex may be a reflection of the disturbed central control of ventilation.

Acoustic Stimulation↗
PubMed1985

Postnatal development of auditory function in the chicken revealed by auditory brain-stem responses (ABRs).

Auditory evoked brain-stem responses (ABRs) were recorded from the surfaces of the brain of lightly anesthetized newborn (1-7 days old) and adult (7-9 weeks old) chickens as a measure of the development of auditory processing. One-day-old and older chickens showed a series of waves within 5 msec after the stimulus onset. This precocity of the ABR in chickens contrasts with the first appearance of the ABR in cats at 4 days of age. The ABR onset latency was shorter in adult chickens than in newborns. This indicates that developmental modifications of mechanical transmission in the external and middle ear or cytodifferentiation of the sensory hair cells of the basillar papilla and the neurons of the acoustic nerve continue postnatally. Within the complex wave form of the response, most of the inter-wave latencies decreased with maturation, indicating that development of the central auditory pathway also continues postnatally. One inter-wave latency (N1 to P3-4) was significantly shorter (P less than 0.05) in adults than in newborns for intense click stimuli, and even among newborns, this inter-wave latency was significantly shorter in 6- and 7-day-old specimens than in 1-3-day-old specimens. It seems likely that changes in the N1 to P3-4 inter-wave latency reflect changes in evoked activity of second order auditory neurons that are located in the nucleus angularis and nucleus magnocellularis, and that intensive developmental changes occur in these neurons during the first postnatal week. The ABR recorded in chickens is a reliable measure of functional activity in the auditory system which is reproducible between individuals and capable of demonstrating developmental changes in specific segments of the wave form.

Animals↗