M. Ulfendahl et al., MECHANICAL RESPONSE CHARACTERISTICS OF THE HEARING ORGAN IN THE LOW-FREQUENCY REGIONS OF THE COCHLEA, Journal of neurophysiology, 76(6), 1996, pp. 3850-3862
1. With the use of an in vitro preparation of the guinea pig temporal
bone, in which the apical turns of the cochlea are exposed, the mechan
ical and electrical responses of the cochlea in the low-frequency regi
ons were studied during sound stimulation. 2. The mechanical character
istics were investigated in the fourth and third turns of the cochlea
with the use of laser heterodyne interferometry, which allows the vibr
atory responses of both sensory and supporting cells to be recorded. T
he electrical responses, which can be maintained for several hours, we
re recorded only in the most apical turn. 3. In the most apical turn,
the frequency locations and shapes of the mechanical and electrical re
sponses were very similar. 4. The shapes of the tuning curves and the
spatial locations of the frequency maxima in the temporal bone prepara
tion compared very favorably with published results from in vivo recor
dings of hair cell receptor potentials and sound-induced vibrations of
the Reissner's membrane. 5. Compressive nonlinearities were present i
n both the mechanical and the electrical responses at moderate sound p
ressure levels. 6. The mechanical tuning changed along the length of t
he cochlea, the center frequencies in the fourth and third turns being
similar to 280 and 570 Hz, respectively. 7. The mechanical responses
of sensory and supporting cells were almost identical in shape but dif
fered significantly in amplitude radially across the reticular lamina.