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PubMed1986

Effects of presbycusis and other types of hearing loss on auditory brainstem responses.

Auditory brainstem responses were studied in 373 healthy individuals of various ages and with sensorineural hearing loss of differing degrees. 209 subjects were elderly and had a hearing loss which included a component of presbycusis. The remainder were young or middle-aged with cochlear hearing loss. Altogether 606 ears were tested. The old individuals had generally longer ABR wave latencies than the young subjects. The I-V interpeak latency (IPL) was also prolonged in the older age groups compared with the group of younger individuals, except for subjects with pronounced hearing loss. The results of the study indicate that an age-related dysfunction of the auditory pathway in the brainstem can be present in presbycusis.

Adult↗
PubMed1986

Origin of ascending auditory projections to the nucleus mesencephalicus lateralis pars dorsalis in the chicken.

Ascending auditory projections to the nucleus mesencephalicus lateralis pars dorsalis (MLd) were studied in white Leghorn chickens by means of unilateral injections of horseradish peroxidase into the MLd and by injections of tritiated leucine into nucleus angularis or the combined nucleus magnocellularis and nucleus laminaris. The experiments showed that nucleus angularis sends an extensive projection to the contralateral MLd and a smaller projection to the rostral pole of the ipsilateral MLd; the lagenar region contributes to these bilateral connections. Nucleus angularis also projects bilaterally to the superior olive and nucleus ventralis lemnisci lateralis and to the contralateral nucleus lemnisci lateralis pars ventralis and dorsal nucleus of the lateral lemniscus. Projections from nucleus laminaris were demonstrated to the ipsilateral superior olive, to the contralateral lemniscal nuclei and a small medial region in MLd bilaterally; the contralateral projection is much denser than the ipsilateral one. Other nuclei having ascending connections with MLd include the contralateral superior olive, the ipsilateral nucleus lemnisci lateralis pars ventralis, the contralateral nucleus ventralis lemnisci lateralis and the contralateral MLd. The ipsilateral superior olive and nucleus ventralis lemnisci lateralis also project to MLd but much more sparsely than in their contralateral projection. Although several of these findings correspond with auditory connections previously shown in the pigeon brainstem, they differ fundamentally in that we find both nucleus angularis and nucleus laminaris projecting to different areas of the MLd on both sides of the brain. In particular, our observation that the cochlear nucleus has bilateral connections with MLd demonstrates an important avian similarity with the brainstem auditory pathways of other terrestrial vertebrates.

Animals↗
PubMed1995

Effects of maternal preeclampsia on brain-stem auditory evoked response in very low birth weight infants.

OBJECTIVE: Because stress in utero may enhance neuromotor maturation, we hypothesized that infants born to mothers with preeclampsia would have a shorter absolute latency V and interpeak latency I-V period (brain-stem conduction time) of brain-stem auditory evoked response (BAER) than infants born to normotensive mothers. STUDY DESIGN: A retrospective cohort study was performed to assess the effects of maternal preeclampsia on BAER of very low birth weight infants. The cohort consisted of 24 infants with a birth weight less than 1251 gm born to mothers with preeclampsia, and 48 infants born to normotensive mothers, matched for birth date within 2 months, gestational age, and chronologic age at the time of the BAER test. The BAER test was completed before discharge, with the infant in a quiet state and the use of a 30 dB stimulus. RESULTS: The mean latencies of wave V were shortened bilaterally (left 8.60 +/- 0.6 msec vs 9.02 +/- 0.6 msec, p < 0.008; right 8.61 +/- 0.6 msec vs 8.96 +/- 0.6 msec, p < 0.033, and the interpeak latency of I-V was significantly shortened compared with the control subjects on the left (left 4.91 +/- 0.5 msec vs 5.38 +/- 0.6 msec, p < 0.003; right 5.17 +/- 0.5 msec vs 5.37 +/- 0.6 msec, not significant). CONCLUSION: These results suggest that the intrauterine stress of maternal preeclampsia accelerates the maturation of the auditory nerve and brain-stem auditory pathway in very low birth weight infants.

Adult↗
PubMed1984

Visual evoked potentials and brain stem auditory potentials in Friedreich's ataxia--a longitudinal study.

Six patients with Friedreich's ataxia, 4 males and 2 females, their ages ranging from 13 to 33 years, were studied. The early manifestations started between age 7 and 13 with an evolution time between 6 and 20 years. Serial visual and brain stem auditory evoked potential recordings were made. A progressive increase in latency, reduction in amplitude and in latency inter-ocular difference of P100 were observed. The pattern of the reversal checker-board visual evoked potential was preserved. A disorganized BAEP pattern, a well defined potential I, a very small potential V and a delay in the interpeak latency were constant findings. The assumption is made of a progressive involvement of both visual and central auditory pathways. Pathophysiological mechanisms are discussed.

Adolescent↗
PubMed2002

Vocal-acoustic circuitry and descending vocal pathways in teleost fish: convergence with terrestrial vertebrates reveals conserved traits.

Vocal behavior is multifaceted and requires that vocal-motor patterning be integrated at multiple brain levels with auditory, neuroendocrine, and other social behavior processes (e.g., courtship and aggression). We now provide anatomical evidence for an extensive vocal network in teleost fishes (Batrachoididae: Porichthys notatus; Opsanus beta) that is strongly integrated with neuroendocrine and auditory pathways and that exhibits striking similarities to the vocal-acoustic circuitry known for mammals. Biotin compound injections into neurophysiologically identified vocal regions of the forebrain (preoptic area and anterior hypothalamus) and of the midbrain (periaqueductal gray and paralemniscal tegmentum) reveal extensive connectivity within and between these regions, as well as reciprocal relationships with the auditory thalamus and/or auditory midbrain (torus semicircularis). Thus, specific components of the basal forebrain and midbrain are here designated as the forebrain vocal-acoustic complex (fVAC) and midbrain vocal-acoustic complex (mVAC), respectively. Biotin injections into the mVAC and a previously identified hindbrain vocal pattern generator likewise provide anatomical evidence for a distributed network of descending projections to the vocal pacemaker-motoneuron circuitry. Together, the present experiments establish a vocal-auditory-neuroendocrine network in teleost fish that links the forebrain and midbrain to the hindbrain vocal pattern generator (i.e., fVAC --> mVAC --> pattern generator) and provides an anatomical framework for the previously identified neuropeptide modulation of vocal activity elicited from the forebrain and midbrain, which contributes to the expression of sex- and male morph-specific behavior. We conclude with a broad comparison of these findings with those for other vertebrate taxa and suggest that the present findings provide novel insights into the structure of conserved behavioral regulatory circuits that have led to evolutionary convergence in vocal-acoustic systems.

Animals↗
PubMed1986

Evoked potential components in the layers of the auditory cortex of the cat.

The intracortical distribution of evoked potentials was studied by seven-contact multielectrodes implanted into the primary auditory cortex of freely moving cats. The aim of the study was to compare the intracortical profiles of the responses evoked by click stimuli and by electrical stimulation of the medial geniculate body in different states of alertness and in Nembutal anesthesia. Only the early surface positive component showed phase reversal in the depth of the cortex. The middle latency components which were faithful indicators of vigilance appeared without phase reversal. Nembutal wiped out these components. A negative component of about 50 ms latency appeared in the attentive animal which had the highest amplitude close to the surface and decreased toward the depth indicating that it was generated in the most superficial layers of the cortex. The stimulation of the last nucleus of the specific auditory pathway elicited evoked potential patterns including also the middle latency components, which were closely similar to those induced by click stimuli.

Animals↗
PubMed1985

Combined electrophysiological and autoradiographic delimitation of retrocochlear dysfunction in a mouse mutant.

The hereditary retrocochlear dysfunction in the quivering (qv) mouse was investigated with autoradiography and single unit recordings. Whilst the cochlea appears to function normally, earlier studies had indicated some single unit dysfunction detectable at the level of the cochlear nucleus (CN) and abnormality of auditory evoked potentials recorded at the inferior colliculus (IC). The present study investigated the possibility of progressive deterioration of function at successive higher levels in the auditory system. The 2-deoxyglucose technique illustrated auditory activity in the CN of quivering mice similar to that seen in normally-hearing control animals. There was only a slight increment in metabolic activity detectable at the level of the IC. Electrophysiology demonstrated that this minimal IC activity was the result of abnormally raised thresholds associated with all single units recorded, rather than of activity in a few normally responding cells. There was no evidence from autoradiography for any enhanced auditorily evoked metabolic activity in either the superior olivary complex or the lateral lemniscus. This study suggests that the retrocochlear dysfunction in quivering mice is due to a specific abnormality at a low stage in the auditory pathway rather than being non-specific and cumulative over stages.

Animals↗
PubMed1985

Pathway and hemispheric differences in the event-related potential (ERP) to monaural stimulation: a comparison of schizophrenic patients with normal controls.

Previous research has established the stability of the contralateral dominance effect of the auditory temporal N120 peak amplitude. The purpose of this experiment was to examine event-related potential (ERP) asymmetries in schizophrenia, with particular reference to this contralateral dominance phenomenon. Ten unmedicated schizophrenic patients and ten controls heard a series of monaural tones, with no task requirements, while EEG was recorded from Cz, Pz, T3, and T4 referred to linked earlobes. Patients were characterized by smaller N120 amplitudes than controls, an effect that was slightly more pronounced at temporal sites. Patients failed to show the normal N120 contralateral dominance effect. Hemisphere asymmetry ratios revealed that 50% of the patients showed ipsilateral dominance in the auditory pathways. Furthermore, the hemisphere asymmetries (whether ipsilaterally or contralaterally dominant) seen in patients were significantly greater than for controls. These data offer a new level of explanation for schizophrenic performance abnormalities in dichotic listening paradigms and an explanation for for the apparent dichotomy in patient performance between exaggerated right ear advantage (REA) and left ear advantage (LEA).

Acoustic Stimulation↗
PubMed2002

Auditory neural responses to click stimuli of different rates in the brainstem of very preterm babies at term.

Auditory neural responses to acoustic stimuli of different rates were studied by analyzing changes in brainstem auditory evoked responses (BAER) with increasing repetition rate of clicks, or rate-dependent changes, in 62 very preterm babies (gestation 24-32 wk). None had perinatal asphyxia or major complications at the time of testing (37-42 wk postconceptional age) to exclude their possible effects on the recorded BAER. As the rate of clicks was increased from 21/s to 51/s and 91/s, I-V interpeak interval in these babies increased similarly to that in normal term neonates. The rate-dependent change decreased significantly in I-III interval, but increased significantly in III-V intervals and III-V/I-III interval ratio (all p < 0.01). At all three rates of clicks, the I-V interval, the most commonly used BAER variable, tended to increase slightly but did not differ significantly from the term neonates. The I-III interval decreased significantly at higher click rates (ANOVA p < 0.05 at 51/s and < 0.001 at 91/s), whereas the III-V interval and III-V/I-III interval ratio increased significantly at all 21/s, 51/s, and particularly 91/s (p < 0.01-0.001). No abnormalities were found in wave V amplitude at any rates. These results suggest that very preterm babies have an advanced peripheral development of the brainstem auditory pathway but a retarded central development or central impairment. A nearly normal I-V interval does not exclude a possible abnormality in its subcomponents (I-III and III-V intervals). In babies who have a normal BAER at a conventionally used low rate of clicks, we cannot exclude an abnormal BAER at higher rates.

Acoustic Stimulation↗
PubMed1984

Auditory brainstem anomalies in albino cats: II. Neuronal atrophy in the superior olive.

In a previous paper (Brain Res., 260:1-9, 1983) we reported that albino cats show abnormal auditory brainstem evoked responses that appear to arise from structural defects in or near the superior olivary complex. In the present study, neuronal cross-sectional area in brainstem nuclei was compared in albino and normally pigmented adult cats. The albinos were true tyrosinase-negative (cc) and should not be confused with the deaf white cat (W); the albinos are not deaf. Neurons in the medial superior olivary nucleus (MSO) of albinos were, on average, 41% smaller than in pigmented animals; there was no overlap in the neuronal size distributions for the two groups of animals. Cell size in the lateral superior olive, medial nucleus of the trapezoid body, ventral nucleus of the lateral lemniscus, anteroventral cochlear nucleus, dorsal cochlear nucleus, and facial nucleus was also smaller (by 9-21%) in albinos than in pigmented animals but none of these differences was statistically reliable. In the abducens nucleus, neurons were 12% larger in albinos than in pigmented animals, demonstrating that neuronal size in the albinos is not uniformly smaller. Several lines of evidence suggest that the auditory system defects in albinos are related to abnormal pigmentation rather than to other gene effects. It is possible that a subtle pigment-related disruption of inner ear development in albinos results in a central cascade of atrophic changes along the auditory pathway.

Animals↗
PubMed1995

[The study of factors affecting ABR in high risk newborn infants].

A.B.R. was employed to examine auditory pathways in a group of 78 newborn infants at risk and one of 20 normal infants. The impaired newborn group suffered of various risk factors or pathologies: 20 premature infants, 12 undersize (small for date), 12 with breathing distress, 11 hiv positive, 5 with neonatal jaundice, 4 suffered of convulsion, 4 at risk for hereditary deafness, 4 born by mothers with mellitus diabetes, 2 with dolichocefalia, 1 with the Albers-Schomberg syndrome, 1 with congenital heart disease and 1 with congenital glycogenosis. The results of A.B.R. of the risk group were compared statistically employing the "t Student's test" with those of the group of normal infants. The influence of risk factors in the first group on alterated A.B.R. parameters was then examined using a step-by-step logistic regression analysis method. The result showed a significant increase in a latency of waves V and III and inter-waves I-V and III-V in risk infants, while wave I and I-III internals were normal. These findings appear to demonstrate that in infants at risk, brainstem acoustic pathways are more sensitive to damage than the cochlea and acoustic nerve. This could be explained by the different degree of maturation that exists between the central acoustic pathways and the coclea and acoustic nerve. Analysis of the influence of pathologies and risk factors on A.B.R. indicate that birth weight followed by chronological age and length of the gestation period are significant in the development of A.B.R. alterations. The Albers-Schomberg syndrome, dolicocephalia, microcephalia, congenital glicogenosys, hiv infection, breathing difficulty and neonatal jaundice proved to be the main pathologies responsible for bringing about A.B.R. alterations.

Auditory Pathways↗
PubMed1988

Neuroanatomical distribution of receptors for three potential inhibitory neurotransmitters in the brainstem auditory nuclei of the cat.

In order to visualize the relative abundance of each of three potentially inhibitory neurotransmitters in the nuclei of the brainstem auditory pathway, receptor sites for glycine, GABA-A, and muscarinic acetylcholine (ACh) have been localized in the cat's brainstem auditory system. Conventional autoradiographic receptor-binding procedures were used and the distributions of the receptors were inferred from the respective distributions of tritiated strychnine, muscimol, and quinuclidinyl benzilate (QNB) binding sites. The results show that glycine may be the major inhibitory neurotransmitter in the auditory system as it ascends to the midbrain in that relatively high levels of strychnine binding are present in every major nucleus of the system. In contrast, high levels of muscimol binding of high-affinity GABA-A receptors are confined mostly to the dorsal cochlear nucleus, the dorsal nucleus of the lateral lemniscus, and the central and cortical regions of the inferior colliculus, while high levels of QNB binding of muscarinic ACh receptors are seen only in the central and cortical regions of the inferior colliculus.

Animals↗
PubMed1986

GABA immunoreactivity in the primary nuclei of the auditory central nervous system.

Structures containing gamma-amino butyric acid (GABA) were investigated in the guinea pig cochlear nuclei and superior olivary complexes by means of an immunohistochemical procedure using an antibody directed against GABA. Immunoreactivity was observed in cell bodies of the superficial layers of the ventral and dorsal cochlear nuclei, in lateral superior olive, in some neurons of the medial superior olive, in lateral preolivary nuclei and in the lateral nucleus of the trapezoid body. Fibers and profiles exhibiting GABA immunoreactivity were found in almost all regions of the lower auditory pathways. The abundance of GABA in these regions indicates an important role of this inhibitory amino-acid in the auditory brainstem.

Animals↗
PubMed2003

Clinical usefulness of laser-evoked potentials.

In contrast to the function of the visual or auditory pathways which are electrophysiologically accessible by visual or auditory evoked potentials, the somatosensory pathway cannot be investigated as a whole by conventional somatosensory evoked potentials (SEP), because these only reflect function of large fibers, dorsal columns, medial lemniscus and their thalamo-cortical projections mediating sensations like touch and vibration. The other half of the somatosensory system, signaling temperature and pain perception, uses a different set of afferents and different central pathways, the function of which is accessible by laser-evoked potentials (LEPs). LEP can document lesions of the spinothalamic tract and (lateral) brainstem and of thalamo-cortical projections conveying thermo-nociceptive signals. In the peripheral nerve, LEP can help distinguish between large and small fiber neuropathies. The rapid heating of the skin by infrared laser pulses can easily be applied to non-glabrous skin in any dermatome. In recent years, many clinical studies have demonstrated that LEP can supply evidence for establishing clinical diagnoses when deficits of the nociceptive system are present. This review outlines principles and recording techniques for LEP in patients and compiles typical LEP findings in patients with lesions due to different diseases at various levels of the nociceptive pathways. Limitations for the use of LEP are pointed out, too, like the uncertainty of lesion location along these pathways and the fact that LEP can reliably show correlates of reduced nociceptive function but only rarely of enhanced transmission (like in hyperalgesia).

Electric Stimulation↗
PubMed1999

Brainstem auditory evoked potentials among rubber factory workers.

The study was conducted on 27 rubber factory workers for the functional assessment of brainstem auditory pathway. Neurobehavioural questionnaire was administered to the workers and the personal sampler was used to evaluate the respirable particulate load inhaled per day of each worker along with qualitative analysis for PAH compounds. Evoked potential recording was carried out for brainstem auditory responses. Chest X-rays of workers exhibited varied abnormal features. Multiple regression analysis of data showed definite prolongation of latencies with increasing concentration of respirable particulate load though it was not statistically significant. Comparison with normative data indicated prolongation of latencies of rubber factory workers.

Adult↗
PubMed1996

Representation of frequency in the primary auditory field of the barn owl forebrain.

1. The primary auditory field (PAF) constitutes the first telencephalic stage of auditory information processing in the classical auditory pathway. In this study we investigated the frequency representation in the PAF of the barn owl, a species with a broad frequency range of hearing and a highly advanced auditory system. 2. Single- and multiunit sites were recorded extracellularly in ketamine-anesthetized owls. The frequency response properties of PAF sites were assessed with the use of digitally synthesized dichotic stimuli. PAF sites (n = 442) either were unresponsive to tonal stimulation (but responsive to noise stimuli), were tuned for frequency, or had multipeaked frequency response profiles. Tuned sites responded best to frequencies between 0.2 and 8.8 kHz, a range that encompasses nearly the entire hearing range of the barn owl. Most sites responding best to frequencies < 4 kHz had relatively broad frequency tuning, whereas sites responding best to higher frequencies had either broad or narrow frequency tuning. Sites with multipeaked frequency response profiles typically had two response peaks. The first peak was usually between 1 and 3 kHz and the second was usually between 5 and 8 kHz; there was no systematic relationship between the two peak frequencies. 3. In dorsoventral electrode penetrations that contained sites with tuned and/or multipeaked response profiles, a "common frequency" was identified that elicited a maximal response from all of the sites in the penetration. 4. The PAF contains a single tonotopic field. Units tuned to low frequencies are located caudomedially, whereas units tuned to high frequencies are located rostrolaterally. Compared with the frequency representation along the basilar papilla and in other auditory structures, the PAF overrepresents low frequencies (< 4 kHz) that are important for barn owl vocalizations. Conversely, high frequencies (> or = 4 kHz), which are necessary for precise sound localization, are underrepresented relative to these more peripheral auditory structures. 5. There was considerable interindividual variability both in the relative magnification of different frequency ranges and in the orientation of the tonotopic map in the brain. 6. These results suggest that the barn owl PAF, like the mammalian primary auditory cortex, is a general processor of auditory information that is involved in the analysis of both the meaning (such as species-specific vocalizations) and the location of auditory stimuli. In addition, the high degree of interindividual variability in the representation of frequency information suggests that the barn owl PAF, like the mammalian auditory cortex, is subject to modification by sensory experience.

Acoustic Stimulation↗
PubMed1994

Fos-like immunoreactivity elicited by sound stimulation in the auditory neurons of the big brown bat Eptesicus fuscus.

C-fos immunocytochemistry was used as a rapid and sensitive technique for identification of sound activated neurons in the cerebral cortex, the cerebellum and subcortical nuclei of the big brown bat, Eptesicus fuscus. When bats were stimulated with sounds under the both-ears opened conditions, Fos-like immunoreactive neurons were bilaterally and symmetrically distributed in all subcortical auditory nuclei, the auditory cortex, the superior colliculus, the pontine nuclei and the cerebellar deep nuclei. Interestingly, when bats were stimulated with sounds under the monaurally plugged conditions, a larger (31-74% more) number of Fos-like immunoreactive neurons were observed. They were predominantly distributed in all contralateral auditory nuclei from the level of the nucleus of the lateral lemniscus down and in all ipsilateral auditory nuclei from the level of inferior colliculus up as well as in the contralateral superior colliculus, pontine nuclei and cerebellar deep nuclei. Implications of these observations in relation to known mammalian auditory pathways and electrophysiological studies are discussed.

Acoustic Stimulation↗
PubMed1994

Attention and otoacoustic emissions: a review.

The possible existence of an attention effect on the peripheral auditory system remains a controversial issue. The aim of the present study is to show the possible contribution of otoacoustic emissions towards demonstrating cognitive control of peripheral auditory processes via the auditory efferent fibers. This measurement technique allows investigation of a further part of the peripheral auditory pathways and of whether efferent fibers, presumably involved in cochlear neurosensory activity, could mediate an attention effect by the selection of auditory information.

Acoustic Stimulation↗