An adaptive model simulating the somatic motility and the active hair bundle motion of the OHC.

The outer hair cells (OHC) of the mammalian inner ear change the sensitivity and frequency selectivity of the filtering system of the cochlea using two kinds of mechanical activity: the somatic motility and the active hair bundle motion. We designed a non-linear adaptive model of the OHC employing both mechanisms of the mechanical activity. The modeling results show that the high sensitivity and frequency selectivity of the filtering system of the cochlea depend on the somatic motility of the OHC.

Physiologically inspired signal preprocessing for auditory prostheses: insights from the electro-motility of the OHC.

We designed a non-linear functional model of the outer hair cell (OHC) functioning in the filtering system of the cochlea and then isolated from it two second-order structures, one employing the mechanism of the somatic motility and the other the hair bundle motion of the OHC. The investigation of these circuits showed that the main mechanism increasing the sensitivity and frequency selectivity of the filtering system is the somatic motility. The mechanism of the active hair bundle motion appeared less suitable for realization of the band-pass filtering structures due to the dependence of the sensitivity, natural frequency and selectivity on the signal intensity.

[Peptides regulating food intake and body weight].

Regulation of food intake and body weight depends on direct and feedback signals from adipose tissue, alimentary canal and pancreas to the hypothalamus nuclei, where hunger and satiety centers are. During the last decade a few signaling molecules of peptide origin were discovered, which play an important role in the regulation of energy intake and energy expenditure as well as in obesity. So, adipocytes synthesize and express leptin, the product of Ob gene, a regulator of long-term food intake, in amounts proportional to the fat amount, while alimentary canal hormones are regulators of short-term food intake (from meal to meal).

Compression, adaptation and efferent control in a revised outer hair cell functional model.

In the cochlea of the inner ear, outer hair cells (OHC) together with the local passive structures of the tectorial and basilar membranes comprise non-linear resonance circuits with the local and central (afferent-efferent) feedback. The characteristics of these circuits and their control possibilities depend on the mechanomotility of the OHC. The main element of our functional model of the OHC is the mechanomotility circuit with the general transfer characteristic y=ktanh(x-a).

A multi-channel adaptive nonlinear filtering structure realizing some properties of the hearing system.

An adaptive nonlinear signal-filtering model of the cochlea is proposed based on the functional properties of the inner ear. The model consists of the cochlear filtering segments taking into account the longitudinal, transverse and radial pressure wave propagation. On the basis of an analytical description of different parts of the model and the results of computer modeling, the biological significance of the nonlinearity of signal transduction processes in the outer hair cells, their role in signal compression and adaptation, the efferent control over the characteristics of the filtering structures (frequency selectivity and sensitivity) are explained.

A non-linear circuit for simulating OHC of the cochlea.

In the present paper, referring to known characteristics of the outer hair cells functioning in the cochlea of the inner ear, a functional model of the outer hair cells is constructed. It consists of a linear feed-forward circuit and a non-linear positive feedback circuit. The feed-forward circuit reflects the contribution of local basilar and tectorial membrane areas and passive outer hair cells' physical parameters to the forming of low-selectivity resonance characteristics.