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Results for “Auditory Pathways”

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At least 163 records · Page 9Linked to original sources
PubMed1990

[Clinical and electrophysiological studies of the organ of hearing in newborn infants. II. Study of maturity of the auditory pathway by brain stem responses (ABR) in newborn infants].

In a group of 130 tested children, 102 of whom a property had evaluated on brain stem responses, we tested the influence of newborn maturation on values of response parameters, their configuration and threshold values. It was shown that newborn maturation lowers in a statistically significant way the threshold values of acoustic stimulus. Also, the configuration of the monitoring changes with age of child tested. Newborn maturation increases the frequency of occurrence of waves II, IV, V and VI though decreases of incidence IV/V complex. In the group of the youngest pre-term babies IV/V complex were present in 50% of cases, whereas in the group of newborns carried to term its present could be verified only in 5-11% of cases. Newborn maturity also influences in an essential way the average latent time consecutive waves as well as central conduction time determined by interpeak latency I-V. Coefficient correlation values for these parameters shows a negative statistical significance correlation. That is, a decreasing of average values of these parameters with maturation of the newborn. It was also shown that structures of the hearing pathway responsible for generation of early and late components of brain stem responses nature at different periods. Peripheral structures of the hearing pathway are significantly more mature at birth than are central structures.

Age Factors↗
PubMed1978

Sound localization: value in localizing lesions of the auditory pathway.

Reports in the literature suggest that patients with otosclerosis, neural lesions such as acoustic neuroma, pontine lesions, and temporal lobe lesions may show abnormal sound localization ability. In the present experiment, 15 normal subjects and 22 patients with various auditory pathway lesions had sound localization testing using special apparatus. The results confirmed that patients with otosclerosis were unable to localize low frequency sounds. Those with temporal lobe lesions made judgments not significantly different from normal subjects. Patients with unilateral sensorineural deafness made errors localizing high frequency sounds. Those with acoustic neuromas made greater errors than those without, but the difference between these two groups just failed to reach statistical significance. The number of cases was however small, and further studies are in progress to attempt to define numerical criteria to assist clinical decisions with regard to the selection of patients for invasive investigations such as oil cisternogram.

Deafness↗
PubMed2001

Of delays, coincidences and efficient coding for space in the auditory pathway.

To localize a sound source in space, the auditory system detects minute differences in the arrival time of a sound between the two ears. It has long been assumed that delay lines and coincidence detectors turn these time differences into a labelled line code for source position, but recent studies challenge this view.

Animals↗
PubMed1997

Ultrastructure of synaptic contacts between identified neurons of the auditory pathway in Gryllus bimaculatus DeGeer.

The synaptic contacts between the auditory sensory cells and identified auditory interneurons ON1 and AN2 have been examined at the ultrastructural level by selective electron-dense labeling of two interneurons or of one interneuron and the sensory fibers in the same preparation. The experiments have provided the following information. The auditory afferent fibers have a monosynaptic connection with the lateral inhibitors ON1 and the ascending interneuron AN2, allowing direct activation of these interneurons. Furthermore, our work proves that the paired, lateral, inhibitor ON1 neurons have direct output synapses onto each other. The results also show that the auditory afferent axons, themselves, receive synaptic inputs just before entering the central auditory neuropil. The effects of current injection into the ON1 neuron during auditory processing indicate that these synaptic inputs onto the afferents originate, in part, from the lateral branches of the ipsilateral ON1 neuron and that they have inhibitory function. The significance of these results for auditory processing and a future perspective for electron microscopic analysis of neuropil are discussed.

Animals↗
PubMed1975

Auditory localization: role of auditory pathways in brain stem of the cat.

Cats were trained to localize sound in space. The animals' localization accuracy was determined before and after one of the following operations: 1) transection of the trapezoid body, 2) unilateral and 3) bilateral transection of the lateral lemniscus, 4) unilateral and 5) bilateral transection of the brachium of the inferior colliculus. The results after bilateral transections of the lateral lemniscus and the one deep bilateral transection of the brachium of the inferior colliculus indicate that some portion of the ascending auditory system must be intact above the medulla for an animal to be able to localize sound. A small loss in accuracy of localization was found after unilateral transection of the lateral lemniscus or brachium of the inferior colliculus. This loss, when compared with the much larger loss that monaural animals show, is an indication that binaural analysis, important for sound localization, occurs at the level of the medulla. Some transections of the trapezoid body resulted in a deficit in localization ability that appeared to be complete and permanent. The position of the lesions in the trapezoid body indicated that important encoding of the binaural cues to localization most likely occurs at the superior olivary complex, probably at the medial superior olive. But the trapezoid body or other commissures of the brain stem auditory system are probably also involved in transmission of information necessary for localization to higher centers.

Animals↗
PubMed1992

Development of brainstem auditory pathway in mallard duck embryos and hatchlings.

The development of the brainstem auditory evoked potential (BAEP) was studied in mallard duck (Anas platyrhynchos) embryos and hatchlings from 5-6 days before hatching through two days after hatching in response to tone pips of different frequencies. BAEPs showed a different time of onset and a different rate of development for low, middle, and high frequencies. Although auditory sensitivity in the mid-frequency range (1.0, 1.5, 2.0, and 3.0 kHz) appeared 1-2 days later than in the low-frequency range, development of the BAEPs in the mid-frequency range was almost complete by hatching. In contrast, the development of auditory sensitivity in the low- and high-frequency ranges continued to develop after hatching. Accelerated development of BAEPs to middle frequencies during the embryonic period and to high frequencies after hatching was correlated with the ducklings' exposure to their own mid-frequency and high-frequency vocalizations before and after hatching, respectively.

Aging↗
PubMed1992

Reticular formation influences on primary and non-primary auditory pathways as reflected by the middle latency response.

Ongoing studies are aimed at identifying the neural pathways responsible for the middle latency response (MLR). These studies involve the analysis of surface and intracranial potentials following pharmacologic inactivation (with lidocaine) of discrete regions of the guinea pig brain. Previous investigations have shown that MLR surface waves recorded over the temporal lobe originate from pathways anatomically and functionally distinct from those that generate MLR waves recorded over the midline, and that both primary and non-primary auditory thalamo-cortical pathways contribute to the guinea pig MLR. The present investigation examines the role of the mesencephalic reticular formation (mRF) in the MLR generating system. Inactivation of the mRF was associated with disruption of the midline response. These waves have been shown to reflect activity from non-primary subdivisions of the thalamo-cortical pathway. Components recorded over the temporal lobe were also affected, consisting of amplitude reduction and latency prolongation without changes in response morphology. Changes in temporal MLR components with mRF inactivation were smaller than those associated with direct inactivation of primary and non-primary subdivisions of the medial geniculate body. These findings indicate that mRF input is essential for normal generation of those components of the MLR thought to reflect both primary and non-primary auditory pathway activity.

Animals↗
PubMed1975

[Directional hearing, temporal order, auditory pattern: new methods of symptomatological study of the central auditory pathways. Physiological data].

New tonal audiometry tests: directional hearing, temporal order and hearing pattern were experimented in 50 healthy subjects with normal hearing. These tests involve the ability to integrate and elaborate complex tonal stimuli at the central pathway level, in addition to the perception of tonal stimuli. The method and apparatus employed are described. In spite of the complexity of the latter, the tests are rapid and easily understood by the subject. They are thus suitable for extension from the laboratory into clinical practice. Their use has shown that the central routes display a variety of capabilities at different levels, of both dynamic and static type; the former are evaluated by the directional hearing test, the latter by the other two tests.

Adult↗
PubMed1988

[Organogenesis of hearing. Ontogenesis of the auditory pathways].

A general review of the bibliography concerning the embryonic development of the auditory receptor provides a better knowledge of this topic, and anatomical basis of prenatal hearing, the existence of which has recently been demonstrated. The auditory receptor appears to be functional from the second trimester of pregnancy, but hearing seems mainly possible after 35 weeks.

Animals↗
PubMed1981

Neural delay in the ascending auditory pathway.

Evoked responses from the cochlea and cochlear nucleus in the rat were studied using two types of stimuli: (1) bursts of tones or noise, and (2) continuous tones or noise that were amplitude modulated with pseudorandom noise. While the responses to the first type of stimuli were averaged only in the conventional way, the responses to the continuous and amplitude modulated sounds were averaged over one period of the pseudorandom noise. This average was then cross correlated with one period of the noise. The morphology of these cross correlation functions was in many ways similar to the response to transient sounds. Recordings from the round window of the cochlea and the cochlear nucleus showed that the latencies of these peaks in the responses to tone bursts and those of the cross correlation functions obtained from the continuous tones modulated with pseudorandom noise were similar. However, the latencies of the peaks in the cross correlation functions were slightly shorter and showed less dependency on the stimulus intensity than did the peaks in the responses to tone bursts. When the responses to noise bursts and the responses to noise that was amplitude modulated were compared, it was found that the latencies of the peaks in the cross correlation functions were nearly independent of the stimulus intensity. However, the peaks in the averaged responses to noise bursts showed a decrease in latency with increasing sound intensity.

Animals↗