Takuji Koike

Measurement of stapes mobility in guinea pigs and rabbits

In tympanoplasty, it is essential to know the condition of the stapes. However, it has been difficult to evaluate stapes mobility in routine measurement. With the eye on improving future clinical practice, in this study we developed a new, easy system of measuring stapes mobility quantitatively and, as a first step, applied it to measurement of the relationship between the load and displacement of the stapes in guinea pigs and rabbits. The stapes displacement increased linearly with an increase in load in the small displacement region, and increased nonlinearly in the large displacement region. The slope of the regression line of this stiffness curve in the small displacement region was used as an index of the stapes mobility. The values in the guinea pigs and rabbits were 16+/-7 N/m and 115+/-25 N/m, respectively. A significant difference between the two species was observed.

Relationship between the levels of DP components and non-active portions of the basilar membrane: Simulation using human cochlear finite-element model

In this study, a three-dimensional finite-element model of the human cochlea was created considering the non-linear activity of the outer hair cells (OHCs) to investigate the mechanism of the development of distortion product otoacoustic emissions (DPOAEs). Two tones with frequencies of f1 and f2 were simultaneously applied to the stapes head of the model, and distortion components generated on the basilar membrane (BM) and at the stapes were calculated. The results suggested that the activity of the OHCs at the more basal part of the BM compared to the characteristic frequency position of f2 has critical roles to generate DPOAEs.