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PubMed1997

Brain stem auditory-evoked response in relation to neonatal glucose metabolism.

Imprecise control of glucose homeostasis is a hallmark of neonatal glucose metabolism. A relatively wide range of glucose concentrations is considered 'euglycemic' (2.22-6.94 mmol/l, 40-125 mg/dl) in the neonatal period. We investigated the effects of a wide range of glucose concentrations on brain stem conduction time (BCT) I-V interpeak latency or prolonged wave V latency. Neonates were assessed by brain stem auditory-evoked response followed immediately by heelstick sampling to determine the blood glucose concentration. Twenty-seven appropriate for gestational age (AGA) term neonates (birth weight 3,245 +/- 766 g, mean +/- SD; gestational age 39 +/- 2 weeks) were studied 3.1 +/- 3.7 days after birth. Twenty-three AGA preterm neonates (birth weight 2,175 +/- 477 g; gestational age 35 +/- 1 weeks) were studied 6.0 +/- 7.2 days after birth. Brain stem conduction time wave I-V interpeak latency and wave V latency were determined in two trials using a Grason-Stadler ABR screener at a 60-decibel stimulation level in the right ear. Neonates were studied between 33 and 40 weeks gestational age. Although the blood glucose concentration ranged from 1.38 to 6.83 mmol/1 (25-123 mg/dl), there was no correlation between either brain stem conduction time wave I-V interpeak latency or wave V latency and blood glucose concentration. We conclude that alterations in glucose concentration within the generally accepted neonatal euglycemic range do not effect the functional status of the brain stem auditory pathway. We suggest that the data can be interpreted to affirm that tighter clinical control of glucose homeostasis is probably not required in the neonatal period.

Birth Weight↗

PubMed2005

[The study of early auditory evoked potentials in primary headaches in children and adolescents and their pathogenetic implications].

UNLABELLED: Neurophysiological examinations, especially auditory evoked potentials which enable us to make the neurophysiological evaluation of the auditory pathway play an important role in the explanation of pathophysiology of primary headaches, especially migraine. The functional neuroimaging studies in patients with migraine during pain attacks have shown the activation of brainstem. It is suggested that the appearance of photophobia in patients with migraine may be related to the disturbances of brainstem functions. The aim of the studies was to evaluate the brainstem auditory evoked potentials (BAEP) in children with primary headaches. The obtained results were interpreted with consideration of the complex pathomechanism of migraine. MATERIAL AND METHODS: 125 patients participated in these examinations with 90 ones with migraine and 35 ones with tension-type headache (TTH), diagnosed according to the criteria of the International Headache Society (IHS). The control group for neurophysiological examinations consisted of 66 healthy children and adolescents of the same age. BAEP were recorded using 4-channel Multiliner (Toennies, Germany). The following parameters were evaluated: morphology of the recording, absolute latencies of I to V waves and interlatencies between I-III, III-V and I-V. RESULTS: Essential prolongation of latencies in III and IV waves of BAEP was found only in patients with migraine, especially with visual aura. They were significant in comparison to latencies obtained in children with TTH and in the control group. No correlations between the clinical data from patients with migraine and TTH, and neuropsychological parameters were found. CONCLUSIONS: 1. The significant prolongation of III and IV wave latencies of BAEP was found in migraine patients only. The obtained results suggest that the brainstem contributes to the pathomechanism of these headaches. 2. The BAEP recordings in children and adolescents with TTH were not different from the parameters obtained in healthy children.

Adolescent↗

PubMed1981

[Speech audiometry in advanced age - differentiating between the elements of primary and secondary presbyacusis (author's transl)].

Tone threshold, speech intelligibility by the Freiburg test with loss of hearing for speech, discrimination loss and total word intelligibility, dichotic discrimination and binaural summation ability were all measured in 167 test subjects aged between 65 and 91 years. The statistical processing of the numerous parameters shows that all parameters manifest a worsening of hearing with age, the individual values revealing a considerable scatter. Tone loss proved to be largely cochlear in nature. All the speech audiometric parameters correlated highly significantly (binaural summation significantly) with age, in the sense that increasing was accompanied by a worsening of the hearing ability. The complex correlations among all the hearing parameters lead us to believe that ageing affects the organ of hearing as a whole, and not merely specific parts of the auditory pathway. A possibility for differentiating between the elements of primary and secondary presbyacusis, and for measurement of the biological age of the sense organ, ear, is discussed.

Age Factors↗

PubMed2005

Asymmetry in corticofugal modulation of frequency-tuning in mustached bat auditory system.

Focal electric stimulation of the auditory cortex is well suited for exploration of the function of the corticofugal (descending) system and the neural mechanism of plasticity in the central auditory system, because it evokes changes in frequency-tuning, called best frequency (BF) shifts, as does auditory fear conditioning. The Doppler-shifted constant frequency (DSCF) area of the primary auditory cortex of the mustached bat is highly specialized for fine frequency analysis. Focal electric stimulation of the DSCF area evokes the BF shifts of ipsilateral cortical and collicular neurons away from the BF of stimulated neurons, whereas the stimulation evokes the BF shifts of contralateral cortical and collicular neurons either toward or away from the stimulated BF. The direction of contralateral BF shifts shows a flip-flop, depending on the spatial relationship between the stimulated and recorded neurons. This asymmetry in corticofugal modulation is mostly, if not totally, created by two subdivisions of the stimulated DSCF area that transmit signals to the contralateral DSCF area, presumably through the corpus callosum. This intriguing asymmetry in corticofugal modulation presumably functions for equalization of the reorganization of the frequency maps of the DSCF areas and subcortical auditory nuclei on both sides.

Acoustic Stimulation↗

PubMed1984

[Neuronal populations in the posterior group of thalamic nuclei projecting into the amygdaloid complex and auditory cortex in the cat].

Location of neurons in posterior thalamic nuclei and neighbouring structures of the midbrain regions projecting to the amygdaloid complex and auditory cortex of cat was studied by the method of horseradish peroxidase. The main sources of these brain region projections to amygdaloid complex are peripeduncular , subparafascicular and suprageniculate nuclei and caudal division of the medial geniculate body. The cells of origin of projections to the auditory cortex are located in all medial geniculate nuclei and wide regions of the posterior thalamic group. Neuron pools projecting to the auditory cortex and amygdala exist in medial parts of the posterior thalamic nuclei. The role of posterior thalamic nuclei in transmission of auditory signals to amygdala is discussed.

Amygdala↗

PubMed1990

Promontory electrical stimulation in labyrinthectomized ears.

Bilateral deafness can occur in patients with Menière's disease who have undergone a labyrinthectomy in one ear. To investigate the feasibility of a cochlear implant in the labyrinthectomized ear, promontory electrical testing by transtympanic needle was performed in six patients who had undergone a unilateral transmastoid labyrinthectomy 6 weeks to 5 years previously. All patients had a behavioral response to the stimulus, and each described a different pitch percept with the four frequencies used. Five of the patients demonstrated an electrically evoked middle latency response. These data are comparable with behavioral and electrophysiologic responses from ears deafened by other causes and now successfully implanted. The results suggest that peripheral neural elements and central auditory pathways remain at least partially functional many years after a labyrinthectomy. Thus, a labyrinthectomy should not be withheld as a surgical option if otherwise indicated.

Adult↗

PubMed1992

Brainstem auditory evoked potentials during procaine toxicity in dogs.

Although the toxic effect of local anaesthetics on the activity of cerebral cortex has been extensively studied, little is known about their toxic effect on brainstem. Accordingly, the influence of procaine on brainstem auditory evoked potentials (BAEPs) and on the electroencephalogram (EEG) was observed in 15 dogs. After the administration of procaine (15 mg.kg-1, i.v.), the amplitudes of wave I (1.88 +/- 0.56 vs 2.06 +/- 0.61 microV, mean +/- SD) and wave II (1.91 +/- 0.41 vs 2.06 +/- 0.46 microV) in BAEPs increased (P less than 0.05), while the amplitudes of wave III (0.97 +/- 0.27 vs 0.81 +/- 0.24 microV), wave IV (1.15 +/- 0.43 vs 0.85 +/- 0.29 microV) and wave V (1.04 +/- 0.46 vs 0.92 +/- 0.41 microV) were decreased (P less than 0.05), and both the I-III inter-peak latency (1.57 +/- 0.04 vs 1.70 +/- 0.07 msec) and III-V inter-peak latency (2.15 +/- 0.09 vs 2.35 +/- 0.12 msec) were prolonged (P less than 0.01). The EEG changed from an awake pattern to seizure activity. These results suggest that the electrical activity of the brainstem auditory pathway is suppressed even when the cerebral cortex is in an excitatory state at the convulsive stage of procaine toxicity.

Animals↗

PubMed2004

Dissociable functional cortical topographies for working memory maintenance of voice identity and location.

In order to ascertain whether the neural system for auditory working memory exhibits a functional dissociation for spatial and nonspatial information, we used functional magnetic resonance imaging and a single set of auditory stimuli to study working memory for the location and identity of human voices. The subjects performed a delayed recognition task for human voices and voice locations and an auditory sensorimotor control task. Several temporal, parietal, and frontal areas were activated by both memory tasks in comparison with the control task. However, during the delay periods, activation was greater for the location than for the voice identity task in dorsal prefrontal (SFS/PreCG) and parietal regions and, conversely, greater for voices than locations in ventral prefrontal cortex and the anterior portion of the insula. This preferential response to the voice identity task in ventral prefrontal cortex continued during the recognition test period, but the double dissociation was observed only during maintenance, not during encoding or recognition. Together, the present findings suggest that, during auditory working memory, maintenance of spatial and nonspatial information modulates activity preferentially in a dorsal and a ventral auditory pathway, respectively. Furthermore, the magnitude of this dissociation seems to be dependent on the cognitive operations required at different times during task performance.

Acoustic Stimulation↗

PubMed1996

Effects of intratympanically delivered lidocaine on the auditory system in humans.

Since lidocaine is used to relieve the symptoms of Meniere's disease and tinnitus, its effects on the human cochlea is of specific interest. In experimental animals, topically administered lidocaine affects cochlear electrophysiology in a specific, dose-dependent manner. In the current study, lidocaine (40 mg in 1 ml of saline) was delivered intratympanically in six patients with essentially normal hearing in an attempt to alleviate tinnitus. Auditory function was assessed by pure tone audiometry, auditory evoked brain stem responses (ABR), and transiently evoked otoacoustic emissions (TEOAE) to observe possible drug effect in the auditory system. In five patients, saline was injected prior to lidocaine for control purposes. Saline injection did not create significant changes in any of the measures. After a 2 hr follow-up period, intratympanic injection of lidocaine caused a 2 to 10 dB reduction in TEOAE level at 1 to 3 kHz frequencies. This reduction was at its maximum at the 30 min post-injection sampling point, and was followed by a slow recovery. At 2 hr post-injection, TEOAE amplitude was still 2 to 4 dB below baseline level. Pure tone thresholds were slightly affected 30 min after intratympanic lidocaine injection, but were fully recovered 1 hr after the injection. Lidocaine injection did not cause any changes in ABR latencies or amplitudes in any of the patients. These results suggest that the dose of intratympanically administered lidocaine used here has a specific effect on the organ of Corti structures in human subjects, without significantly affecting the auditory nerve or central auditory pathways. The relationship of the drug effect in conjunction with a possible effect on inner ear disorder might help to localize the site of disorder.

Acoustic Stimulation↗

PubMedDate not supplied

Effects of inhaled carbon disulfide on sensory-evoked potentials of Long-Evans rats.

Peripheral nerve conduction time and parameters of potentials evoked from brain by somatosensory, auditory, and visual stimulation were studied as a function of the concentration of carbon disulfide (CS2) chronically inhaled by female Long-Evans rats. Thirty rats were divided into three groups of ten each and exposed to air or 400 or 800 ppm CS2 7 hours per day, 7 days per week, for 11 weeks. Stimuli consisted of tail shock, clicks, tone pips, light flashes, and reversing visual patterns to evoke multisensory potentials. Effects were observed on conduction time in the periphery, in brainstem auditory pathways and in the visual system. The effects on pattern-reversal potentials were greater than those on flash-evoked potentials.

Action Potentials↗

PubMed1982

Effects of sodium pentobarbital, ketamine, halothane, and chloralose on brainstem auditory evoked responses.

A parametric study was performed in cats comparing the effects on the brainstem auditory evoked response of four anesthetic agents used either in the operating room or the laboratory: sodium pentobarbital, ketamine, halothane, and chloralose. Each anesthetic agent was administered to each of four cats in varying sequence. Click-evoked brainstem auditory evoked responses (BAER) were compared for differences in wave form configuration, latencies, and amplitudes of the component peaks. Five distinct peaks (I to V) could be identified in the brainstem auditory evoked responses of every animal using each anesthetic agent. There were no statistically significant differences in mean latencies of the component peaks among anesthetic agents. Amplitude differences of the component peaks between animals using the same anesthetic agent were too large to be meaningfully compared. This study suggests that the click-evoked brainstem auditory response is a useful means of monitoring the integrity of the ascending auditory pathway during neurosurgical procedures as the wave form and latencies of the component peaks are not affected by a variety of parenteral and inhalation anesthetic agents.

Animals↗

PubMed1993

Acute and long-term effects of adrenocorticotropin and dexamethasone on the auditory brainstem response in multiple sclerosis patients.

Auditory brain-stem responses (ABRs) were compared in two groups of multiple sclerosis (MS) patients receiving standard treatment with adrenocorticotropin (ACTH) and with dexamethasone (DEX). ABRs were recorded prior to treatment, on the 1st and 8th day of therapy, and 21 days after the hormonal treatment had been discontinued. ABRs in MS patients were within the normal range of variability. Latencies of ABR components increased with increasing rate of presentation, and with decreasing intensity of the click stimuli. Changes in ABRs displayed a consistent pattern in patients treated with ACTH, but showed less coherence after DEX. In ACTH treated patients' latencies of the late ABR waves V and Vn were prolonged after clicks of high intensity, and reduced following clicks of low intensity resulting in a decreased slope of the latency-intensity function of these ABR waves. This pattern became most prominent in the recordings after the treatment had been discontinued, and could reflect an improved transmission across both afferent excitatory and recurrent inhibitory synapses in the auditory pathways. The findings indicate that--besides a common anti-inflammatory action--therapies with ACTH and DEX differ with regard to their influence on central nervous functioning.

Adolescent↗

PubMed1991

Brainstem auditory evoked potential study in children with autistic disorder.

Brainstem auditory evoked potentials were compared in 109 children with infantile autism, 38 with autistic condition, 19 with mental retardation, and 20 normal children. Children with infantile autism or autistic condition had significantly longer brainstem transmission time than normal (p less than .001). Autistic features, rather than age, sex, or lower mentality, correlated with brainstem transmission time (p less than .0001). The autistic characteristics may be related to dysfunction of the brainstem which affects the processing of the sensory input through the auditory pathway. The brainstem lesion may be part of a generalized process of neurological damage that accounts for the deviant language, cognitive, and social development in the spectrum of autistic disorder.

Autistic Disorder↗

PubMed2001

Second-order modulation detection thresholds for pure-tone and narrow-band noise carriers.

Modulation perception has typically been characterized by measuring detection thresholds for sinusoidally amplitude-modulated (SAM) signals. This study uses multicomponent modulations. "Second-order" temporal modulation transfer functions (TMTFs) measure detection thresholds for a sinusoidal modulation of the modulation waveform of a SAM signal [Lorenzi et al., J. Acoust. Soc. Am. 110, 1030-2038 (2001)]. The SAM signal therefore acts as a "carrier" stimulus of frequency fm, and sinusoidal modulation of the SAM signal's modulation depth (at rate f'm) generates two additional components in the modulation spectrum at fm - f'm and fm + f'm. There is no spectral energy at the envelope beat frequency f'm in the modulation spectrum of the "physical" stimulus. In the present study, second-order TMTFs were measured for three listeners when fm was 16, 64, and 256 Hz. The carrier was either a 5-kHz pure tone or a narrow-band noise with center frequency and bandwidth of 5 kHz and 2 Hz, respectively. The narrow-band noise carrier was used to prevent listeners from detecting spectral energy at the beat frequency f'm in the "internal" stimuli's modulation spectrum. The results show that, for the 5-kHz pure-tone carrier, second-order TMTFs are nearly low pass in shape; the overall sensitivity and cutoff frequency measured on these second-order TMTFs increase when fm increases from 16 to 256 Hz. For the 2-Hz-wide narrow-band noise carrier, second-order TMTFs are nearly flat in shape for fm = 16 and 64 Hz, and they show a high-pass segment for fm = 256 Hz. These results suggest that detection of spectral energy at the envelope beat frequency contributes in part to the detection of second-order modulation. This is consistent with the idea that nonlinear mechanisms in the auditory pathway produce an audible distortion component at the envelope beat frequency in the internal modulation spectrum of the sounds.

Adult↗

PubMedDate not supplied

Transtympanic and surface recordings in the diagnosis of retrocochlear disorders.

A series of patients presenting with subsequently surgically confirmed central tumour involving the auditory pathways were investigated using both transtympanic electrocochleography (TT ECochG) and surface recordings of brainstem evoked responses (BER). While ECochG allows a detailed study of peripheral function, BER allow the investigation of neural conduction up to the level of the inferior colliculus. Valuable information can be obtained from: (1) comparison of the amplitudes of the sensory and neural components of the ECochG; (2) comparison of ECochG, BER and auditory thresholds; (3) time interval measurements between the auditory nerve response (N1 on the ECochG) and the inferior colliculus (wave P4-5 on BER); (4) contralateral comparisons. Similar measurements performed in pure cochlear pathologies, mainly in Meniere's disease, yielded very significant differences.

Audiometry↗

PubMed1994

Effects of surgical stimulation on midlatency auditory evoked potentials during general anaesthesia with propofol/fentanyl, isoflurane/fentanyl and flunitrazepam/fentanyl.

During general anaesthesia, midlatency auditory evoked potentials are suppressed in a dose dependent manner by a number of general anaesthetics. The activating effects of surgical stimuli on midlatency auditory evoked potentials have been demonstrated during light inhalational anaesthesia, and indicate that midlatency auditory evoked potentials reflect the activity of the central nervous system and not only anaesthetic concentrations. We investigated the effect of surgical stimulation (skin incision, sternotomy) on midlatency auditory evoked potentials under high dose opioid analgesia in 30 patients undergoing elective cardiac surgery. High dose opioid analgesia was maintained using fentanyl (1.2 mg.h-1) and combined with either propofol (4-8 mg.kg-1.h-1) (group I, n = 10), isoflurane (0.6-1.2 vol%) (group II, n = 10) or flunitrazepam (1.2 mg.h-1) (group III, n = 10). Midlatency auditory evoked potentials were recorded in the awake state, during general anaesthesia before skin incision, after skin incision and after sternotomy. During general anaesthesia there were marked statistically significant increases in latencies and decreases in amplitudes of midlatency auditory evoked potentials in the propofol/fentanyl and isoflurane/fentanyl groups. In contrast, in the flunitrazepam/fentanyl group there were only small changes of midlatency auditory evoked potentials. The latencies of the early cortical potentials were similar to those in the awake state. After skin incision as well as after sternotomy no significant changes of midlatency auditory evoked potentials could be observed in any of the experimental groups. These results indicate that activation of the auditory pathway by surgical stimuli may be blocked when analgesia is provided by high dose fentanyl.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗

PubMed2004

Evaluation of hearing thresholds in 3-month-old children with a cleft palate: the basis for a selective policy for ventilation tube insertion at time of palate repair.

Hearing thresholds in children with a cleft palate prior to cleft palate repair are not widely documented, and audiological criteria for short-term ventilation tube insertion do not exist. The aims of this prospective study are to estimate hearing thresholds in 40 children with a cleft palate by 3-month developmental age with auditory brainstem responses (ABRs) under natural sleep and to estimate a hearing threshold guideline for short-term ventilation tube insertion. Our results show a wide range of air conduction hearing thresholds using click ABRs (2-4 Hz), which ranged from 25 to 102 dBnHL in the left ear and from 25 to 80 dBnHL in the right ear with means of 53 and 49 and standard deviations of 17 and 13 respectively. The bone conduction thresholds ranged from 0 to 55 dBnHL with a mean of 26 and a standard deviation of 13. Eighty-three per cent of children had flat, type B, on high-frequency tympanograms, indicative of middle ear effusion. Thirty per cent of the infants had a cleft palate associated with a known syndrome. Currently, it is the authors' practice to use short-term ventilation tubes on a selective basis at the time of cleft palate repair when there is a conductive hearing loss of more than 55 dBnHL in the better ear as determined by ABR with type B high-frequency tympanograms. This threshold level takes into account electrophysiological and auditory pathway maturation discrepancies. With this as the guideline, between 28% and 35% of the children in this study would be eligible for surgery. This criterion still requires further validation.

Acoustic Impedance Tests↗

PubMed2004

Auditory hypersensitivity in children and teenagers with autistic spectrum disorder.

OBJECTIVE: To verify if the clinical behavior of auditory hypersensitivity, reported in interviews with parents/caregivers and therapists/teachers of 46 children and teenagers suffering from autistic spectrum disorder, correspond to audiological findings. METHOD: The clinical diagnosis for auditory hypersensitivity was investigated by means of an interview. Subsequently, a test of the acoustic stapedial reflex was conducted, and responses to intense acoustic stimulus in open field were observed. RESULTS: Of the 46 subjects, 11 (23.9%) were clinically diagnosed as oversensitive to sound and only 2 showed discomfort when exposed to intense acoustic stimulus in open field. There was no statistically significant difference for the test of the ipsilateral acoustic stapedial reflex between the groups. CONCLUSION: Behavioral manifestations to sounds are not associated to hypersensitivity of the auditory pathways, but instead these are associated to difficulties in the upper processing, involving systems that usually are impaired in autistic spectrum patients, such as the limbic system.

Acoustic Stimulation↗