The temporal response of auditory-nerve (AN) fibers to a steady-state vowel is investigated using a computational auditory-periphery model. The model predictions are validated against a wide range of physiological data for both normal and impaired fibers in cats. The model incorporates two parallel filter paths, component 1 (C1) and component 2 (C2), which correspond to the active and passive m...

Inner ear sensory hair cells convert mechanical stimuli into electrical signals. This conversion happens in the exquisitely mechanosensitive hair bundle that protrudes from the cell's apical surface. In mammals, cochlear hair bundles are composed of 50-100 actin-filled stereocilia, which are organized in three rows in a staircase manner. Stereocilia actin filaments are uniformly oriented with t...

The sensory hair cells of the inner ear undergo apoptosis after acoustic trauma or aminoglycoside antibiotic treatment, causing permanent auditory and vestibular deficits in humans. Previous studies have demonstrated a role for caspase activation in hair cell death and ototoxic injury that can be reduced by concurrent treatment with caspase inhibitors in vitro. In this study, we examined the pr...

T sensation of balance and hearing is initiated by the conversion of the movement of stereocilia in hair cells of the inner ear into electrical signals in nerve fibers leading to the brain. Driven by pressure waves that are generated by sound, head movement, or gravity, this transformation of energy occurs in structures of exceptional delicacy and intricacy, where movements of atomic dimensions...

It is often assumed that at frequencies in the tuning-curve tail there is a passive, constant coupling of basilar-membrane motion to inner hair cell (IHC) stereocilia. This paper shows changes in the phase of auditory-nerve-fiber (ANF) responses to tail-frequency tones and calls into question whether basilar-membrane-to-IHC coupling is constant. In cat ANFs with characteristic frequencies > or ...

For sounds of a given frequency, spiral ganglion neurons (SGNs) with different thresholds and dynamic ranges collectively encode the wide range of audible sound pressures. Heterogeneity of synapses between inner hair cells (IHCs) and SGNs is an attractive candidate mechanism for generating complementary neural codes covering the entire dynamic range. Here, we quantified active zone (AZ) propert...

The activity of individual afferent neurones in the mammalian cochlea can be driven by neurotransmitter released from a single synaptic ribbon in a single inner hair cell. Thus, a ribbon synapse must be able to transmit all the information on sound frequency, intensity and timing carried centrally. This task is made still more demanding by the process of binaural sound localization that utilize...

In humans, the absence or irreversible loss of hair cells, the sensory mechanoreceptors in the cochlea, accounts for a large majority of acquired and congenital hearing disorders. In the auditory and vestibular neuroepithelia of the inner ear, hair cells are accompanied by another cell type called supporting cells. This second cell population has been described as having stem cell-like properti...

The auditory epithelium in birds and mammals consists of a postmitotic population of hair cells and supporting cells. Unlike mammals, birds can regenerate their auditory epithelia after trauma. Recent evidence indicates that supporting cells undergo mitosis after acoustic trauma, suggesting that supporting cells may transdifferentiate into hair cells. The goals of this study were to 1) characte...

Auditory afferent fibre activity in mammals relies on neurotransmission at hair cell ribbon synapses. Developmental changes in the Ca(2+) sensitivity of the synaptic machinery allow inner hair cells (IHCs), the primary auditory receptors, to encode Ca(2+) action potentials (APs) during pre-hearing stages and graded receptor potentials in adult animals. However, little is known about the time co...