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Biomedical subjects

W L Rutten

Publications and source records attributed to W L Rutten.

32 records · Page 2Linked to original sources
PubMed1987

Acoustic transfer characteristics in human middle ears studied by a SQUID magnetometer method.

The middle-ear transfer characteristics for sound in 14 human temporal bones were determined using a SQUID magnetometer method. With this method, the cochlea and middle ear remain intact. Postmortem changes were studied using a guinea pig. The mass-loading effects of the applied magnets were determined and were found to be negligible. The mean umbo displacement was equal to the mean of six other studies. Lever ratios varied between the individual temporal bones and as a function of frequency.

Acoustic Stimulation↗
PubMed1986

The influence of cochlear hearing loss and probe tone level on compound action potential tuning curves in humans.

The effect of cochlear hearing loss and of probe tone level on slopes and sharpness of compound action potential tuning curves was investigated. Thirty-one simultaneously masked isoreduction (50%) tuning curves were determined in 26 adults with cochlear hearing losses up to 60 dB. Probe tone frequency was 2 or 3 kHz. Probe tone level was chosen as close as possible to the action potential threshold, usually within 30 dB. In 5 cases a second tuning curve was determined at a 20-30 dB higher probe tone level in order to differentiate between effects of hearing loss and of probe tone level itself on decrease of selectivity. Tuning was analysed in terms of high- and low-frequency slopes of the tuning curves, both in the steepest parts near the tip and overall, and in terms of Q10dB. Slopes and tuning quality diminished with increasing hearing loss up to 60 dB. Part of the decrease in Q10 could be attributed to increased probe tone level, implying that frequency selectivity is also a level-dependent property. In the same group of subjects so called 'narrow-band' (or 'derived response') compound action potential latencies were determined at 90 dB pe SPL and a derived frequency similar to the probe tone in the tuning curve experiments. Narrow band latencies did not change significantly out of the normal range (2 periods) with increasing hearing loss. This implies that narrow band latencies are not related to hearing loss, but reflect only the probe-level dependent impulse response delay. Analysis shows that it is possible to derived Q10dB from narrow band latencies with probe level as a parameter.

Audiometry, Evoked Response↗
PubMed1986

Model evaluation using electroencephalography and magnetoencephalography.

The source of both the measured visual evoked potentials and the measured visual evoked magnetic fields was estimated by means of an inverse procedure. The model used consisted of a single current dipole positioned in a volume conductor consisting of four concentric spheres. Comparison of the results showed that the estimations did not always match. In order to reveal a possible cause of this mismatch a realistically shaped multicompartment model of the head was constructed. From forward simulations it followed that the influence of the realistic shape was apparent, especially when the dipole was positioned deep within the brains.

Electroencephalography↗
PubMed1983

AP unmasking and AP tuning in guinea pig.

Using a method introduced by Harris [6] AP unmasking was investigated in normal guinea pigs. AP unmasking existed in every guinea pig investigated and proved to be stable over measuring periods as long as 7 h. The average standard deviation of unmasking magnitude was 12%. AP unmasking strength was defined as the average unmasking magnitude across across suppressor levels from 0 to 100 dB SPL at constant masker and test-tone level and constant masker, test-tone and suppressor frequency. The relation between AP unmasking strength and AP thresholds was investigated. AP unmasking strength decreases with increasing AP threshold at the suppressor frequency. No relation with AP thresholds at other frequencies was found. AP unmasking areas were determined along with the corresponding AP tuning curves. High-frequency unmasking was found to be more prominent and more stable than low-frequency unmasking in guinea pig. From a comparison with other studies on AP unmasking and single fibre two-tone suppression it was concluded that a species difference exists with regard to the presence of low-frequency AP unmasking and low-frequency single fibre two-tone suppression.

Acoustic Stimulation↗
PubMed1982

AP unmasking and AP tuning in normal and pathological human ears.

In a group of seven normal and eight abnormal hearing subjects three-tone AP unmasking experiments and/or AP tuning experiments were performed during electrocochleography. In the unmasking experiments the Shannon forward masking paradigm was applied, i.e. two simultaneous tones (the masker and the suppressor) influence a test tone in a forward masking procedure. Frequency and intensity of the suppressor were varied. It appeared that unmasking effects are clearly present, i.e. the suppressor stimulus can reduce masking of the AP. This effect, however, is very variable, in normal ears as well as in pathological ears. AP tuning quality deteriorated with increasing hearing loss but no correlation was found between AP unmasking parameters and hearing loss. It seems that AP suppression areas shift less upward (or not at all) than the AP tuning curve does upon increasing the test tone level. These results raise some questions about the intercorrelation of the triad: hearing loss, quality of tuning and suppression effects, as single fibre experiments and psychophysical investigations suggest.

Action Potentials↗
PubMed1980

Evoked acoustic emissions from within normal and abnormal human ears: comparison with audiometric and electrocochleographic findings.

Input--output amplitude behaviour of evoked acoustic emissions ('echoes') to click- and toneburst stimuli can be approximated by R(tau) alpha SPT(tau) where R is response amplitude, S stimulus amplitude and p(tau) is an exponent dependent on latency tau. p(tau) varies linearly from one to zero for post stimulus times (PST) between 5 and about 25 ms, thus indicating increasing nonlinearity with increasing latency. Latencies of echoes after toneburst stimulation decrease with increasing frequency. The latencies seem to be built up from twice the traveling wave time (from the acoustic source to the cochlear partition site of reception) plus twice the transduction filter response times. Adaptative behaviour of the echo-response on varying interstimulus interval (ISI) is not observed. If echoes are present, with frequency fECHO, audiogram losses at fECHO do not exceed 15 dB. Compound action potential (AP) thresholds, obained by electrocohleography (ECoG) confirm this 15 dB criterion and indicate that the 15 dB loss should be of cochlear origin.

Action Potentials↗