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Biomedical subjects

H J Krogh

Publications and source records attributed to H J Krogh.

10 recordsLinked to original sources
PubMed1982

Different patterns of harmonics in frequency-following responses.

Preliminary studies (Krogh et al., 1977) indicated pronounced intersubject differences with respect to harmonic distortion in the frequency-following responses (FFRs) elicited by high intensity, low frequency stimuli and recorded by means of surface electrodes from man. In the present investigation it was confirmed that the responses from 10 test subjects could be divided into three significantly different patterns on the basis of the relative amplitudes of the fundamental (first harmonic) and the second harmonic response component as measured by spectral analyses. In three of the subjects the ratio of the fundamental to the second harmonic was greater than 10 dB (which were termed a type I response). In five, the ratio was between 0 and 10 dB (type II response) and in two the second harmonic was equal to or greater than the fundamental (type III response). The possible causes of harmonic distortion if FFRs are discussed, but not definite explanation of the interindividual differences can be given. A psychoacoustical evaluation of the second harmonic distortion using a tone-on-tone octave masking technique (TOM) showed no correlation between TOM results and FFR type in 10 subjects.

Acoustic Stimulation↗
PubMed1978

N1--P2 component of the auditory evoked potential during alcohol intoxication and interaction of pyrithioxine in healthy adults.

The auditory evoked potential was used to assess the effect of alcohol intoxication (1 g/kg) and pyrithioxine (7 mg/kg) on 9 adult subjects. Its components in the latency range 50--250 msec (N1--P2) were studied for 6 g 30 min, during a constant level of alertness. Four periods were considered: alcohol alone, alcohol plus pyrithioxine, pyrithioxine plus alcohol and placebo. With alcohol alone the N1--P2 amplitude was small in the first part of the test and large in the second part as compared to placebo values. Pyrithioxine antagonism was greatest after alcohol had been resorbed. The placebo period indicated that amplitude changes were not due to long-term habituation, when the subject was kept alert.

Adult↗
PubMed1977

The value of some suprathreshold auditory measures.

Factors, both acoustic and non-acoustic, which may influence the Most Comfortable Loudness Level, the Uncomfortable Loudness Level, the Acoustic Reflex Threshold and the Threshold of Overload are reviewed. A direct experimental comparison of these measures was made with respect to their absolute values and the between- and within-subject variances. The Most Comfortable Loudness Level was found to have the greatest within- and between-subject variability. The Uncomfortable Loudness Level, although having high between-subject variability, did not have significantly greater within-subject variability than the Acoustic Reflex Threshold. The significance of these results is discussed.

Acoustic Stimulation↗
PubMedDate not supplied

Monitoring middle ear pressure by tympanometry. A study of middle ear pressure variation through seven hours.

The aim of this investigation was to monitor fluctuations in middle ear pressure, to study tympanometric signs of Eustachian tube functioning and to assess the validity of the tympanometric readings. In 20 patients with a low initial middle ear pressure (-150 daPa or lower) and 5 normals, impedance tympanometry was performed every 3 min through 7 h. Median pressure for the patients was -150 daPa (range 100 to -400 daPa) and for the normals 0 daPa (range 50 to -50 daPa). A remarkable pressure increase was seen after changing the body position to the supine. The patients were arranged into three groups according to the lowest middle ear pressure registered. Median pressures for the groups were running at a rather constant level. However, the individual pressure fluctuations in many patients were so great that a single tympanometric reading has to be considered unreliable when selecting patients for insertion of ventilation tubes. Thirteen patients never equalized their negative middle ear pressure, indicating that their Eustachian tube did not open during the test period. In spite of this the pressure did not decrease to lower values, indicating that maintaining a relative constant middle ear pressure is independent of opening of the Eustachian tube.

Acoustic Impedance Tests↗
PubMedDate not supplied

Eye closure and the acoustic reflex threshold.

Eye closure during measurement of the acoustic reflex threshold has been found on average to lower the threshold by 1.2 dB. It had no significant effect on the intra- or intersubject variability of the measure. It is concluded that it probably has little significance from the standpoint of clinical testing.

Adult↗