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Biomedical subjects

F Böhnke

Publications and source records attributed to F Böhnke.

11 recordsLinked to original sources
PubMed1998

Nonlinear mechanics of the organ of Corti caused by Deiters cells.

Though the organ of Corti (OC) has been an object of experimental and theoretical hearing research, open questions remain concerning the processing of acoustic signals by the cochlea where the OC is located. Today there is extensive knowledge about single parts of the organ but a lack of understanding as to how these elements act together. One of the reasons for this is the missing analysis of the mechanics of the OC in three dimensions. In order to fill this gap, we have analyzed a short section (0.06 mm) of the basilar membrane including the OC and evaluated its nonlinear finite element model numerically. The Deiters cells are idealized as thin elastic beams with a comparably low modulus of elasticity of actin. Therefore, they show nonlinear mechanical behavior generating additional frequency components with two-tone stimulation.

Basilar Membrane↗
PubMed1989

[Correlation of the latency shift and brain stem potentials in basocochlear hearing loss and the time course of the click stimulus-induced evoked wave in the cochlea].

Frequency-specific information on high tone loss in the inner ear can, and if so only indirectly, be obtained from changes in latency of the click-evoked brain stem potential (ABR). The relationship between latency increases of the Jewett-wave-V in basocochlear hearing loss and the time course of the travelling wave on the basilar membrane will be presented. The latency increases of basocochlear hearing loss at 2 kHz, 1 kHz and 500 Hz correspond to both the computer-simulated time course of the travelling wave and to those of the derived responses. From a pathophysiological standpoint, receptor cells in basocochlear hearing loss are not functional, beginning at the oval window, so that, dependent on the degree of inactivity, a delay corresponding to that of the time course of the travelling wave passes until active hair cells are reached and action potentials released that produce, when summed up a potential of delayed latency.

Acoustic Stimulation↗
PubMed1988

Click ABR intensity-latency characteristics in diagnosing conductive and cochlear hearing losses.

A schematic description of the correlation between various pathologies of hearing impairments and the behavior of auditory brainstem responses (ABR) is presented. Conductive pathology and high-frequency cochlear hearing losses prolong wave component latency due to energy loss and hair cell dysfunction. In cases of flat cochlear hearing loss latency is not affected. Prolonged interwave latencies between wave I and wave V indicate eight nerve and brainstem disorders. An algorithm was developed in the form of a flow chart for locating various malfunctions. Fields of wave V intensity-latency functions were designed for the faster detection and more precise evaluation of conductive and cochlear hearing losses.

Algorithms↗
PubMed1988

[Response latency characteristics for ENT medical assessment of auditory brain stem evoked response].

A schematic description of the correlation between the various types of hearing disorders and the behaviour of auditory brain stem responses (ABR) is presented. Conductive pathology and high-frequency cochlear hearing loss prolong wave component latency due to energy loss and hair cell dysfunction. Latency is not affected in flat cochlear hearing loss. Prolonged interwave latencies between wave I and wave V indicate eighth nerve and brain stem disorders. An algorithm in the form of a flow chart was developed for location of the malfunction. Families of characteristics of wave V intensity-latency functions were designed for faster detection and more precise evaluation of conductive and cochlear hearing losses.

Audiometry, Evoked Response↗
PubMed1988

[Effect of cochlear processes in generating Jewett IV and V brain stem potential components].

Polarity of the stimulus influences latency, amplitude and waveform of the human auditory brainstem response (ABR). One clear feature is the splitting of the wave complex JIV and JV in separate peaks following rarefaction stimulation. ABR was recorded using high-pass filtering to mask the basilar membrane partially to establish whether and to what extent basal hair cells contribute to waves IV and V. Wave IV disappeared in response to rarefaction stimuli with masking of the basal region. In contrast, wave V appeared with reduced amplitude and delayed latency in response to condensation stimuli. A model was developed to determine the motion of the basilar membrane and the distribution over time of the action potential on the auditory nerve fibers following rarefaction and condensation stimuli. The rarefaction stimulus produces a bifid and the condensation stimulus only a single-peaked contribution. It is suggested that the splitting of the wave complex IV and V may be traced to mechanical processing in the cochlea.

Auditory Pathways↗
PubMed1987

[Spatial representation of basilar membrane movement with 3D computer graphics].

A mathematical model of the cochlea was implemented on a computer. The basilar membrane motion was computed for single, two, and multi-tone stimuli as well as for musical sounds and vowels. The pattern of the travelling waves were presented in three-dimensional color computer graphics. The high performance 3D graphics system performs local hidden surface removal, 3D geometric transformations and supports local lighting models to generate truly realistic shading for complex 3D objects. An addressable 1280 by 1024 pixel matrix assures crisp, precise resolution of the finest detail in the graphic images. The spatial pattern of basilar membrane motion conveys an impression of the image of acoustic stimuli on the basilar membrane. Firstly, the motion pattern of the travelling wave to a single tone is presented. The superposition of several tones (two-tone, multi-tone) causes a superposition of the travelling waves along the basilar membrane whereby the place principle in the cochlear partition becomes more clearly recognizable. Sounds (flute and violin) and vowels (German "u" and "i") evoke a complex motion pattern on the basilar membrane. The realization of the chronological order of movements on the basilar membrane can be made by computer animation. This enables the analysis of the space-time patterns of complex acoustic stimuli.

Basilar Membrane↗
PubMedDate not supplied

3D-finite element model of the human cochlea including fluid-structure couplings.

The propagation of acoustic waves in the inner ear in vivo could not be quantified completely yet. This is in particular true in conjunction with the micromechanical structures of the organ of Corti, though these data are important for the explanation and discussion of clinical measurements like otoacoustic emissions and auditory brainstem responses. To access these problems a three-dimensional mechanical model of the cochlea including the fluid-structure couplings is developed and evaluated numerically by finite elements. Although the complex cochlear partition is covered by passive mechanical elements, the results fit early experiments (1928), which studied the wave propagation in the cochlea with fresh human cadavers [G. von Békésy: Experiments in Hearing. New York, McGraw-Hill, 1960]. Additionally it is now easy to calculate the mechanical input impedance of the cochlea. These results agree with recent experiments [S.N. Merchant et al.: Hear Res 1996;97:30-45].

Biomechanical Phenomena↗
PubMedDate not supplied

Active nonlinear mechanics of the organ of Corti including the stereocilia-tectorial membrane complex.

There is a large amount of knowledge about the different components of the organ of Corti (OC), but little is known about how these components act together in vivo. To clarify the complex mechanical behavior of the OC, anatomic results are carefully analyzed and used to develop a finite element model of a short section of OC, which includes 8 outer hair cells (OHC) and their supporting structures. The modal analysis shows the frequency-dependent phase reversal of the radial stereocilia displacement. The transient computation confirms the amplification of OC displacements when the ability of the OHC to contract and elongate is considered. The inclusion of a nonlinear function describing the mechanoelectrical transduction in OHC amplifies and distorts the displacement of the OC when it is stimulated by a sinusoidal input pressure function. These results are in agreement with other psychoacoustic, electrophysiologic and otoacoustic measurements.

Biomechanical Phenomena↗