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Biomedical subjects

E Laukli

Publications and source records attributed to E Laukli.

47 records · Page 3Linked to original sources
PubMed1980

Auditory brain-stem electric responses evoked with suprathreshold tone-bursts.

The brain-stem electric responses elicited by tone-bursts with central frequency at octave intervals from 0.5 to 4 kHz and at 80--100 dB HL stimulus levels have been studied in normally hearing subjects and patients with sensorineural hearing loss. Jewett V latencies were considerably prolonged in patients with retrocochlear or central pathology. Latencies from normal and cochlear hearing loss ears were largely independent of thresholds at both the stimulus and other frequencies. The interpretation of response latencies at suprathreshold stimulus levels is discussed. Stimulus frequency should be selected in accordance with the pure-tone audiogram, and ears with prolonged latencies investigated at more than one frequency.

Audiometry↗
PubMed1979

Brain-stem responses of the cat and interaural attenuation.

The early auditory evoked responses have been studied in bilaterally hearing cats, and in animals with hereditary unilateral anacusis. Cross-over stimulation of the hearing ear occurs at an interaural attenuation of 50--50 dB, and all six waves of the responsare present at supra-threshold stimulus levels.

Acoustic Stimulation↗
PubMed1979

BSER-audiometry in difficult-to-test patients.

The results of BSER audiometry in a group of 38 difficult-to-test patients are reported, and the response thresholds compared with previous assessments by conventional audiometric techniques. The frequently severe behavioural disorders of these patients necessitated the use of general anaesthesia. Myringotomy revealed middle ear fluid in 20% of the ears, whilst 26% had significant ocular pathology.

Action Potentials↗
PubMed1979

Early auditory-evoked responses in the cat: rate effects.

The brain-stem electric responses (BSER) of the cat have been evoked with a 4-kHz tone burst at three stimulus intensity levels, and at interstimulus intervals (ISI) varying fromm 500 to 20 ms. Response amplitude and latency have also been compared in different post-natal age groups, and in bilaterally hearing and unilaterally deaf animals. Increasing reptition rates produce greater latency changes in the youngest animals, whilst all age groups show amplitude decrement at shorter ISI, apart from wave III which increases in amplitude, particularly in bilaterally hearing cats at higher stimulus intensity levels. Wave I shows greater amplitude reduction than do the succeeding waves, which may indicate that the primary cochlear nuclei contribute to later waves of the BSER.

Acoustic Stimulation↗
PubMed1978

Bilateral recording of early auditory evoked responses in the cat.

The brain-stem electric responses of the cat evoked by a short 4 kHz tone burst have been differentially recorded between vertex and both ipsilateral and contralateral ear electrodes. Six vertex-positive waves can be recognised in both recordings. Animals with hereditary unilateral anacusis were studied in order to avoid cross-stimulation of the opposite ear. The cochlear microphonic and summating potential can be readily recorded in young animals, occur simultaneously in both tracings, and show polarity inversion at the contralateral electrode. The later neural potentials have the same polarity and practically identical latencies in the ipsilateral and contralateral recordings, whilst the first three brain-stem waves show approximate polarity inversion and variable latency relationships in the two recording situations. It is concluded that none of the brain-stem waves represents electric activity from a discrete generator.

Animals↗
PubMedDate not supplied

Air conduction thresholds after myringoplasty and stapes surgery: a conventional and high frequency audiometric comparison.

A comparison has been made of air conduction thresholds after myringoplasty and stapes surgery for otosclerosis in both the conventional (0.25 to 8 kHz) and high frequency (8 to 20 kHz) ranges. Significant threshold losses occurred in the high frequencies following both procedures. Threshold improvement was significantly greater at the lower frequencies following stapes surgery, while high frequency threshold deterioration was significantly less in the myringoplasty group. High frequency audiometry may prove to be a sensitive monitor of middle ear surgical techniques.

Adolescent↗
PubMedDate not supplied

Frequency specificity of the auditory brainstem responses in the cat.

The auditory brainstem responses evoked by click, noise-burst and tone-bursts have been recorded in the cat, and octave-wide derived bands obtained at 20 and 50 dB RL intensity levels. At near-threshold intensity both the 2 and 4 kHz tone-bursts are frequency specific, while the click and noise-burst ABR contain no contributions below 2 kHz. The principal contribution to the 1 kHz ABR comes from the 2-4 kHz band, while at 0.5 kHz almost the entire response is generated basally. Higher stimulus intensity produces a spread of activity into other bands. Low frequency cochlear function cannot be assessed by this technique.

Animals↗
PubMedDate not supplied

Development of early auditory-evoked responses in the cat.

The post-natal development of the auditory-evoked responses to 1- and 4-kHz tone bursts has been studied in the cat with subcutaneous electrodes and signal-averaging techniques. A cochlear microphonic response antedates the earliest appearance of brain stem potentials by 1 or 2 days, and can be recorded in some animals on the first post-natal day with the 4-kHz stimulus. The earliest brain stem response consists of three or four low-voltage waves,which increase to six in the 2nd week. Latency shortening and amplitude growth occur for all waves, but are most pronounced in the later part of the response. The characteristics of the summating potential, and the variable influence of rate effects on wave amplitude are described for the different age-groups.

Acoustic Stimulation↗
PubMedDate not supplied

Multifrequency tympanometry. Preliminary experiences with a commercially available middle-ear analyzer.

Normal ears and ears affected by various pathologies were studied with a clinical middle-ear analyzer according to the multifrequency tympanometric concept, by which the resonance frequency of the tympanic membrane/middle-ear system can be determined. This frequency varies considerably in normal ears with a mean value close to 1 kHz. Ears with pathologies in the tympanic membrane and otosclerotic ears have resonance frequencies differing significantly from those of normal ears. The effects may be explained by considering mass and stiffness components.

Acoustic Impedance Tests↗
PubMedDate not supplied

Auditory brainstem response in the cat. Effect of masking level on derived-band contributions.

The auditory brainstem responses evoked by 1 and 4 kHz tone-bursts and clicks at stimulus levels 40 dB above response threshold have been recorded in the anaesthetized cat, and octave-wide derived bands were obtained by the differential high-pass masking procedure. Masking level was varied systematically. Raising masking level to maximally 10 dB of over-masking results in a basalward shift of derived-band contributions, the amplitude of both waves I and IV increasing in the highest frequency band and falling in the most apical. Higher masking levels produce an increase in wave latency in the individual bands, which is greatest at the lowest frequencies. Comparable levels of under-masking have opposite but lesser effects.

Acoustic Stimulation↗