Volume 103, Issue 3, March 1998
Index of content:
- PHYSIOLOGICAL ACOUSTICS 
103(1998); http://dx.doi.org/10.1121/1.421291View Description Hide Description
A model based on the potassiumcurrent pathway through the hair cell is used to analyze the electrical behavior of mammalian inner and outer hair cells. Without taking into account the effects of calcium it is possible to simulate experimental results concerning the shape and strength of the receptor potential and the frequency dependent ac(alternating current) and dc (direct current) components of the receptor current. This model and a simplified form of it are utilized to explain: (1) Transduction latencies: that the receptor potential follows a stimulating signal with a very short delay, under the assumption of a constant number of open K channels in the lateral part of the cell membrane. (2) Transduction gains: why higher potential changes are measured in inner hair cells than in outer hair cells, although the outer hair cells are expected to be exposed to higher stereociliary motions: in inner hair cells a decrease in the conductance of the basolateral membrane causes higher gain (receptor potential increases) and together with an increase of membrane capacitance slower reaction (a larger time constant). (3) Transduction channel kinetics: that the shortest (0.1 ms) as well as the longest (20 ms) possible open times of the transduction channels in the stereocilia have different frequency related effects on the shape of the receptor potentials.
Effectiveness of intermittent and continuous acoustic stimulation in preventing noise-induced hearing and hair cell loss103(1998); http://dx.doi.org/10.1121/1.421303View Description Hide Description
Resistance to noise-induced hearing loss (NIHL) was studied in gerbils exposed either to intermittent or continuous low-level noise prior to an intense noise. Auditory-evoked brainstem response (ABR) thresholds, distortion product otoacoustic emissions (DPOAEs), values from compound action potential (CAP) tuning curves, and outer hair cell (OHC) loss were measured for each group. Subjects were exposed to A-weighted noise (octave band noise centered at 2 kHz) on an intermittent (80 dB, 6 h/day) or continuous schedule (74 dB, 24 h/day) for 10 days, allowed to rest in quiet for 2 days, then exposed to intense A-weighted noise (107 dB, 24 h/day) for 2 days. A “noise-only” group was exposed only to the intense noise. Gerbils exposed in both the “intermittent” and “continuous” groups had less (15–30 dB) temporary threshold shift (TTS) than those in the noise-only group. In addition, the continuous group had less (10–15 dB) permanent threshold shift (PTS) than the other groups. These data suggest that resistance to NIHL is evident in both the intermittent and continuous groups when TTS is measured, but resistance to PTS is afforded only by the continuous paradigm. Both paradigms decreased OHC loss as compared to the noise-only group, with the continuous paradigm being most effective. However, neither paradigm conserved DPOAE amplitudes or tuning curve values relative to the noise-only group.