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. 2007 Jan 31;27(5):1006–1014. doi: 10.1523/JNEUROSCI.5452-06.2007

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Copyright © 2007 Society for Neuroscience 0270-6474/07/271006-09$15.00/0

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Figure 3. — A, Transducer current responses (top trace) and TM-loaded fiber motion (bottom trace) measured at different frequencies for an apical-turn IHC, obtained with 1.4 mm calcium in the bath. The driving fiber made contact with the top of the TM, and its displacement was kept constant from frequency to frequency (20, 50, 100, 200, 500, 1000, and 2000 Hz) by adjusting the magnitude of individual voltage bursts to the driver to compensate for small peaks and dips of the response because of the mechanical properties of the vibrating fiber. The recording location was ∼8.6–8.9 mm from the base of the cochlea, representing ∼1–0.6 kHz of the best frequencies in vivo. B, The magnitude (peak to peak) and phase of the current relative to the TM displacement as a function of frequency (data points) is shown. The magnitude plot is normalized to the 2000 Hz response. Magnitude data points are fitted with the real part of the following function:
where ω = 2πf and i = (−1)^1/2. The fitting constants are as follows: R₁ = 1.75 × 10⁷, R₂ = 10⁶, K = 3.7 × 10⁻¹⁰ or A = 0.054, τ₁ = 6.5 ms, τ₂ = 0.35 ms. The imaginary part of the above equation provides the fit to the phase data in the bottom panel without any parameter adjustment. Note that as set up, the high-frequency magnitude asymptote is 1 and the low-frequency asymptote is A = R₂/(R₁ + R₂), which in this case is 0.054. Both low- and high-frequency phase asymptotes are 0. The fitting equation represents a combination high-pass and low-pass filter (or lead–lag network), with a high-pass cutoff frequency at 1/2πτ₁ (24.6 Hz) and a low-pass cutoff frequency at 1/2πτ₂ (454.7 Hz). deg., Degree. C, Adaptation data obtained from an apical IHC. Black thin lines are single-exponential fits to the decaying part of the plots. Filled circles and the heavy black line are obtained by inverse Laplace transform of the frequency response plot shown in B, with step input and scaling with a Boltzmann fit as shown in Figure 1. D, Transducer current responses and TM-loaded fiber motion measured at different frequencies (20, 50, 100, 200, 500, 1000, 2000, and 4000 Hz) for apical (top) and basal (bottom) IHCs. All of the measurements were performed with 1.4 mm calcium in the bath.

graphic file with name zns00507-2815-m02.jpg — A, Transducer current responses (top trace) and TM-loaded fiber motion (bottom trace) measured at different frequencies for an apical-turn IHC, obtained with 1.4 mm calcium in the bath. The driving fiber made contact with the top of the TM, and its displacement was kept constant from frequency to frequency (20, 50, 100, 200, 500, 1000, and 2000 Hz) by adjusting the magnitude of individual voltage bursts to the driver to compensate for small peaks and dips of the response because of the mechanical properties of the vibrating fiber. The recording location was ∼8.6–8.9 mm from the base of the cochlea, representing ∼1–0.6 kHz of the best frequencies in vivo. B, The magnitude (peak to peak) and phase of the current relative to the TM displacement as a function of frequency (data points) is shown. The magnitude plot is normalized to the 2000 Hz response. Magnitude data points are fitted with the real part of the following function:
where ω = 2πf and i = (−1)^1/2. The fitting constants are as follows: R₁ = 1.75 × 10⁷, R₂ = 10⁶, K = 3.7 × 10⁻¹⁰ or A = 0.054, τ₁ = 6.5 ms, τ₂ = 0.35 ms. The imaginary part of the above equation provides the fit to the phase data in the bottom panel without any parameter adjustment. Note that as set up, the high-frequency magnitude asymptote is 1 and the low-frequency asymptote is A = R₂/(R₁ + R₂), which in this case is 0.054. Both low- and high-frequency phase asymptotes are 0. The fitting equation represents a combination high-pass and low-pass filter (or lead–lag network), with a high-pass cutoff frequency at 1/2πτ₁ (24.6 Hz) and a low-pass cutoff frequency at 1/2πτ₂ (454.7 Hz). deg., Degree. C, Adaptation data obtained from an apical IHC. Black thin lines are single-exponential fits to the decaying part of the plots. Filled circles and the heavy black line are obtained by inverse Laplace transform of the frequency response plot shown in B, with step input and scaling with a Boltzmann fit as shown in Figure 1. D, Transducer current responses and TM-loaded fiber motion measured at different frequencies (20, 50, 100, 200, 500, 1000, 2000, and 4000 Hz) for apical (top) and basal (bottom) IHCs. All of the measurements were performed with 1.4 mm calcium in the bath.