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At least 37 records · Page 2Linked to original sources
PubMed1975

Averaged evoked potentials in cats with lesions of auditory pathway.

Averaged evoked activity was recorded from needle electrodes placed at the vertex of the calvaria and adjacent to each bulla in anesthetized cats in response to click stimuli. The portion of the response from 0 to 10 msec was analyzed. Activity during the first 3 msec was greatly reduced on the side ipsilateral to a lesion involving destruction of the cochlea or section of the eighth nerve and its blood vessels. Activity after 4 msec was greatly reduced on the side ipsilateral to destruction of the cochlear nuclei. No effect was found with destruction of both inferior colliculi. The bulla-vertex evoked responses were also compared to those recorded from the round window. The results support the premise that change in the wave-form of the early evoked potential can be used to determine site of loss of acoustic information along the auditory pathway.

Acoustic Stimulation↗
PubMed1975

[Clinical diagnosis of the auditory pathway using different acoustical evoked responses (author's transl)].

Evoked responses originating from cochlea, brain stem, and cortex are clinically used for differential diagnosis of hearing losses. The diagnostic range and the reliability of the different ERA methods are discussed. In our clinic brain stem potentials recorded by a nonsurgical method have been used as a routine audiometric test in more than 900 cases. The procedure has proved to be easier than electrocochleography and gives nearly the same information about cochlear and middle ear function if there is no VIIIth nerve or lower brain stem damage. For topical diagnosis of the lower auditory pathway additional recording of ECoG is necessary. In the examination of a cortical deafness the recording of brain stem potentials yields the same result as the electrocochleography according to Aran (Fig. 2). In a case of an Apallic syndrome (Fig. 3) brain stem potentials are found only for high intensity clicks, and latencies are abnormally increased. The cochlear potentials simultaneously recorded from the promontory are quite normal. So damage of the brain stem is confirmed.

Adult↗
PubMedDate not supplied

Comparison of hearing threshold determined by auditory pathway electric responses and by behavioural responses.

In order to evaluate their reliability for determing the hearing threshold, the cochlear microphonic potentials, the auditory nerve and brain stem neural evoked responses as well as the cortical evoked responses were compared with the behavioural hearing thresholds of the same subjects in the same session. The threshold for recording the cochlear microphonic potnetial was found to be appreciably higher than the behavioral threshold. The threshold for recording the auditory nerve and brain stem responses was within a few decibels of the behavioural threshold. The thresold of the cortical evoked response was several decibels higher. It is concluded that (1) the auditory nerve and brain stem neural evoked responses are the best indicators of hearing threshold; (2) the cortical evoked responses are usually comparable, and (3) all types of evoked responses are indispensable aids in the evaluation of hearing and the determination of site of lesion in the auditory system.

Audiometry↗
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↗
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↗