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Biomedical subjects

E Laukli

Publications and source records attributed to E Laukli.

At least 37 records · Page 2Linked to original sources
PubMed1988

Auditory brainstem responses and extratympanic electrocochleography. A threshold comparison in children.

Electrocochleography (ECoG) and auditory brainstem response (ABR) have been recorded simultaneously in 23 children referred for threshold evaluation. The ECoG electrode is an extratympanic silver ball (Life-Tech) whereas the ABR is recorded with Ag-AgCl surface electrodes. Of the 30 ears investigated according to this protocol, 11 had no response with either technique, and in a further 11 no difference was found between ECoG and ABR thresholds. In the remaining 8 ears, ABR threshold was lower in 6 and the ECoG in 2. We conclude that the extra time needed for cleansing the ear canal and inserting the electrode does not justify the use of ECoG in threshold evaluations, since the ABR alone has the necessary sensitivity.

Adolescent↗
PubMed1986

Low-frequency hearing loss: auditory brainstem response-derived band analysis.

Conventional (0.125-8 kHz) and high-frequency (8-20 kHz) audiometry, together with brainstem response audiometry supplemented with derived-band studies have been performed in 6 patients with sensorineural hearing loss: 1 with narrow-band, 3-4 kHz, and 5 with low-frequency threshold elevations. The derived-band results in the latter indicate that the low-frequency audiometric thresholds are spurious, and represent the low-frequency tails of viable high-frequency neurons. Threshold preservation in the 4- to 8-kHz frequency band proved necessary for generation of a normal auditory brainstem response at suprathreshold stimulus levels.

Adolescent↗
PubMed1986

Frequency specificity of the auditory brainstem responses. A derived-band study.

Auditory brainstem responses evoked by both clicks and 0.5 kHz tone-bursts were recorded using the derived-band paradigm in 10 normal-hearing subjects. The derived-band analyses showed a similar distribution of activity with both stimuli, the largest contributions coming from the 2-4 and 4-8 kHz bands. Neither the click nor the 0.5 kHz tone-burst is a frequency-specific stimulus, and both would appear to be unsuitable for brainstem response audiometric evaluation of the apical cochlea.

Acoustic Stimulation↗
PubMed1985

Auditory brainstem responses of the cat: on- and off-responses.

The auditory brainstem on- and off-responses evoked by tone and noise bursts have been studied in the cat. The number and amplitude of the off-response waves are proportional to the frequency specificity of the on-response, being greatest for the 4-kHz tone burst and smallest for the noise burst. The threshold of the 0.5-kHz off-response is lower than that of the on-response, but the amplitude of the former does not increase at higher stimulus levels. Derived-band studies show that at 4 kHz the on-and off-responses have identical frequency content, the 0.5-kHz off-response is restricted to the 2- to 8-kHz frequency band, while the noise burst off-response is entirely high frequency. The off-response is an on-response and is evoked by acoustic transients from the loudspeaker transducer.

Acoustic Stimulation↗
PubMed1985

Low-frequency sensorineural hearing loss. Brainstem response, speech and high-frequency audiometry.

Four cases of acquired, unilateral sensorineural hearing loss are presented. The low-frequency octave threshold changes are considered compatible with the low-frequency tails of neurons with characteristic frequencies of 2, 4 and 9 kHz. Zero speech discrimination was found in two patients with high-frequency threshold preservation at and above 4 kHz. Normal auditory brainstem responses were obtained in the two patients with low-frequency hearing loss confined to the frequency bands below 2 and 4 kHz respectively. Only wave I could be reliably identified in the two patients with single frequency threshold preservation at 2 and 9 kHz, while both presented a second, low amplitude wave with latency corresponding to our normative values for wave V. The latter may represent a delayed and pathological wave III.

Adolescent↗
PubMed1985

High-frequency audiometry. Normative studies and preliminary experiences.

A new, commercial high-frequency audiometer, Demlar 20K, for measuring hearing thresholds between 8 and 20 kHz has been used routinely in different patient groups and in a control population over the past 3 years. Test-retest studies have shown that this instrument can be used in the clinic with approximately the same degree of reproducibility as in conventional audiometry. While inter-subject variation is comparatively large, repeated evaluations can be performed in individual cases with an acceptable degree of reliability. This techniques can be helpful in differentiating between noise damage and presbycusis. Pre- and post-operative high-frequency audiometry may prove to be of value in the assessment of middle ear surgical techniques.

Adult↗
PubMed1984

Frequency-following responses in the cat.

The frequency-following response was studied in five cats aged 1 week to 3 years. Animals studied had either monaural or binaural hearing. Responses were recorded differentially from vertex and circumaural electrodes to tonebursts at octave intervals from 0.5 to 4 kHz. Thresholds and dynamics of the responses with and without white-noise masking were investigated. Evidence was found to support the view that the cochlear microphonic makes a major contribution to the frequency-following response, while the double frequency-following response to the 0.5 kHz stimulus is neural.

Animals↗
PubMed1983

Remotely recorded cochlear microphonic in the cat.

The cochlear microphonic (CM) was recorded differentially with subcutaneous electrodes at the vertex and a variety of positions on the head and neck of the cat, and the phase and amplitude were compared with simultaneous recordings from vertex and contralateral ear electrodes. Recordings were made in bilaterally hearing animals, both with and without ear canal occlusion, following unilateral labyrinthectomy, and in white-coat cats with hereditary unilateral deafness, and in different age-groups. The cochlear microphonic was in phase with the contralateral recording at all electrode sites except those in the immediate vicinity of the stimulus ear. The amplitude was less at the circumaural positions and greater at cervical locations. The results were consistent in all age-groups and in bilaterally and unilaterally hearing animals. Precise electrode placement in the near-field conditions around the stimulus ear is therefore critical, especially for phase, while far-field conditions would appear to predominate at the remaining electrode sites.

Animals↗
PubMed1983

Stimulus waveforms used in brainstem response audiometry.

Clicks and tone-bursts are the most widely used stimuli in brainstem response audiometry. The acoustic click waveform is not only dependent on electric pulse length, but also on the type of transducer, ear coupling and measuring method employed. On the other hand, acoustic tone-bursts are more precisely defined by the electric stimulus-parameters since they show less variation under the same experimental conditions. Acoustic cancellation with alternating polarity electric stimuli is also better with tone-bursts.

Acoustic Stimulation↗
PubMed1983

High-pass and notch noise masking in suprathreshold brainstem response audiometry.

The combination of suprathreshold tone-bursts with frequency of 0.5, 1 or 2 kHz and ipsilateral high-pass (HP) or notch noise masking has been studied in 52 adults referred for otoneurological examination on account of unilateral or asymmetric high-frequency hearing loss. Wave V latency changes are similar for both HP and notch noise masking and, in accordance with cochlear tonotopicity, are greater for the lower stimulus frequencies. Results are, however, not always conclusive with either technique, and response identification is problematical at 0.5 kHz. The less demanding HP masking technique is considered the method of choice since possible influence from the stapedius reflex is minimal and a better signal-noise ratio obtained.

Acoustic Stimulation↗
PubMed1981

Development of surface-recorded cochlear and early neural potentials in the cat.

The development of the surface-recorded cochlear and early neural potentials has been studied in the cat from birth to the 8th post-natal week. CM, SP, and each of the neural waves has a characteristic temporal developmental pattern and mature threshold. Wave IV is the most resistant to reduction in stimulus intensity levels, while the thresholds of both cochlear potentials are high. Animals with hereditary unilateral deafness constitute a most convenient model for the study of functional maturation in the auditory pathways, particularly with regard to precise latency estimations.

Aging↗
PubMed1981

Early auditory-evoked responses: filter effects.

The early auditory-evoked responses have been recorded in 4 human subjects and 3 cats using a filter band-pass of 2-5 000 Hz. The responses have been subsequently analogue-filtered at different low-pass and high-pass settings. Reduction of low-pass cut-off produces latency increases of similar magnitudes for all waves. Raising the high-pass cut-off results in dramatic changes in the responses, the peaks of the waves being apparently deflected onto the succeeding wave flanks, thus resulting in false latency reductions. The individual waves are affected at different filter settings dependent on their frequency content.

Acoustics↗
PubMed1981

Early auditory-evoked responses: spectral content.

Spectral analysis of the early auditory-evoked responses in man and in the cat has shown that the predominant contribution to the total power is contained in the band below 50-100 Hz. This low-frequency content is considerably reduced when the corresponding spontaneous brain activity spectrum is subtracted from the response spectrum. Under the latter circumstances, the dominant frequency contribution is found in the 500- to 2,500- Hz bandwidth.

Animals↗
PubMed1980

Identification of early auditory-evoked responses.

Identification of tone-burst-evoked, short-latency auditory responses can be influenced by a variety of factors. Peak definition of the early waves is improved with high-frequency stimuli and at lower filter settings, while contralateral recording facilitates identification of waves IV and V.

Acoustic Stimulation↗
PubMed1980

Ipsilateral and contralateral acoustic reflex thresholds.

A commercially available impedancemeter was modified to permit measurement of hearing thresholds. Both the ipsilateral and the contralateral acoustic reflex thresholds were determined in dB SL in a group of 20 young adults with normal hearing. No significant differences in reflex thresholds were obtained.

Acoustic Impedance Tests↗