Biomedical subjects

M Streppel

Publications and source records attributed to M Streppel.

58 records · Page 4Linked to original sources

PubMed1990

Monitoring the efficiency of hearing aid fitting in the aged by the Social Hearing Handicap Index.

The unsatisfactory results obtained from tone and speech audiometric studies in identifying the effects of hearing disability, in particular the psychosocial factors, prompted us to adopt a psychological test to determine the "social hearing ability". The test consists of 20 questions which all relate to "social hearing ability" in urban society. Ten questions concern hearing ability in situations where background noise plays either a negligible role or none at all. The remaining 10 questions concern selectivity ability, that is hearing with additional background noise. The evaluation of the questionnaire results in a classification of the so-called Social Hearing Handicap Index (SHHI) in percentages together with a breakdown of the deafness components and the selectivity components into percentages. This differentiation provides additional information about the demands placed on the hearing ability of humans in quiet or noisy surroundings. The information obtained from the test enables longitudinal studies on the course of a hearing disability or the effectivity of a particular therapy, e.g. hearing aid, to be carried out in the elderly.

Adult↗

PubMed1990

Monaural and binaural time resolution ability in the aged. A psychoacoustic and electrophysiological study.

Time resolution ability is an important factor of auditory processing, especially in binaural hearing. In psychoacoustical and electrophysiological studies the time resolution of brief modulations of signal amplitude and frequency in monaural hearing, including gap detection ability, was analysed. To reveal the time resolution ability of the binaural hearing system, brief interaural modulations of signal amplitude, short changes of interaural time delay or noise coherence in broadband noise bursts were generated. The sensation levels of these short-lasting changes in the noise structure and the cortical evoked potentials were investigated in young normal hearing subjects and in the elderly. Thus age-dependent changes in monaural and binaural time resolution ability could be detected. For the monaural experiments, lengthened time constants of between 2-20 ms, depending on the degree of intensity or frequency modulation could be derived for older subjects. The binaural experiments were characterized by prolongation between 4-26 ms for short interaural signal delay changes. For both groups the time constants derived from the electrophysiological investigations were more prolonged, which might be explained by masking effects or habituation. Further electrophysiological investigations will be required to differentiate between time resolution processes of brief signal changes within the peripheral and central parts of the auditory system.

Acoustic Stimulation↗

PubMed1990

Fine structure analysis of speech signals. Hearing aids and perceptual training.

Transition and gap detection experiments with synthetic speech stimuli in normal and pathological hearing were carried out to investigate the feasibility of some form of feature-analysing mechanism in speech perception. Identification experiments were performed before the hearing aid fitting, directly thereafter and half a year later to evaluate the important individual cues of speech perception with regard to perceptual training. Possible distortions in the temporal structure of the speech signals by the hearing aids were considered. For our experiments we generated a series of synthetic speech stimuli such as the ba-da-ga sequence, which are identical in their acoustic cues except for the transition of the second formant. The start frequency was changed in nine 200-Hz steps from 800 Hz to 2,400 Hz thus producing a ba at one end of the series and a ga at the other. The phenomenon of categorical perception could be investigated with this set of synthesized speech stimuli. In a second experiment the influence of silent intervals on the identification of plosives was analysed increasing the artificial silent interval in 10 ms steps from 0 ms to 120 ms in speech stimuli like schal thus producing stahl for the 120 ms silent interval. The results of patients with different types of hearing loss fitted with hearing aids are compared with normal hearing. Our investigations show that it will be possible to achieve an integration of fine-structure analysing mechanisms in speech perception into the management and rehabilitation of people with impaired hearing using special speech processors in modified hearing aids and developing special speech and hearing training programs.

Hearing Aids↗

PubMedDate not supplied

Slow axonal regrowth but extreme hyperinnervation of target muscle after suture of the facial nerve in aged rats.

Unilateral transection and suture of the facial nerve was performed in 60 old rats (20 months of age). The time course of mimetic reinnervation was studied by counting all retrogradely labeled motoneurons in the facial nucleus after injection of HRP into the whiskerpad muscles for 14-112 days post operation. The comparison between these neuron counts and data for young rats yielded four conclusions. First, the qualitative equivalent of the phenomenon "misdirected reinnervation" in aged rats was the same as in young adults: HRP-labeled motoneurons were scattered throughout the facial nucleus lacking myotopic organization from 18 until 112 days post operation. Second, no age-related loss of motoneurons was detected. Third, the axonal regrowth was delayed in aged rats. Fourth, the postoperative hyperinnervation (the projection of more motoneurons into a muscle than under normal conditions, i.e., the quantitative aspect of misdirected reinnervation) was more than two times higher than in young rats. These data may provide reasonable explanations for the poor functional recovery after reconstructive surgery on the facial nerve in old patients.

Aging↗