Gao et al. 2014 — Vibration of the organ of Corti within the cochlear apex in mice
Gao et al. used optical coherence tomography (OCT) to image and measure vibrations within intact cochlear tissue in live mice — the first in-vivo OCT vibrometry study of the apical cochlea. Unlike laser vibrometry (single point on BM), OCT provides cross-sectional vibratory maps. Key new finding: the “lateral compartment” (Hensen’s, Boettcher’s, Claudius’ cells lateral to OHCs) shows frequency-dependent phase differences relative to BM, sharply tuned even in postmortem tissue — suggesting passive mechanical tuning by supporting cell architecture.
TL;DR. In-vivo OCT of mouse apical cochlea: BM tuning sharp in live, broad in dead; lateral compartment phase tuned even postmortem; multiple transgenic mouse lines (prestin knockouts, Tecta mutant) confirm passive vs. active contributions. Paper does not report absolute TM or BM displacement values in nm.
Key finding. OCT reveals that the organ of Corti is mechanically more complex than a simple BM + TM two-structure model. Supporting cell region has independent passive tuning. This contextualizes TM displacement estimates: the system has multiple mechanically tuned components.
Numbers that matter
| Parameter | Value | Units | Source location | Conditions |
|---|---|---|---|---|
| BM Q10dB in live CBA mouse | reported (Fig 6) | — | Fig 6A | Frequency-dependent; ~5–10 |
| BM Q10dB in dead mouse | lower than live | — | Fig 6A | Active amplification lost |
| Lateral compartment center frequency Fc | between BM live/dead BF | — | Fig 6B | From phase fit |
| Absolute BM/TM displacement in nm | NOT reported | — | — | Normalized to ossicular chain; no nm absolute values |
| Stimulus levels used | 40–80 | dB SPL | Methods | In vivo mouse |
On TM displacement. This paper does not provide the 5–30 nm values for TM displacement at 60 dB SPL cited in h02 scripts. The OCT data are presented as normalized sensitivity ratios, not absolute nm. For absolute nm estimates, stapes velocity + middle-ear gain scaling would be needed. The 5–30 nm range at 60 dB SPL cited in scripts is broadly consistent with cochlear mechanics literature but requires sourcing from a paper that actually calibrates absolute displacement (e.g., Cooper & Rhode 1996, or Nuttall et al.).
Limitations
- Apical cochlea only (mouse CF ~8–10 kHz at apex studied); basal turn not imaged.
- Lateral compartment measurements are indirect; TM not imaged directly in this paper.
- OCT spatial resolution limits precise localization within the OC cross-section.
Connections
[source]tectorial-membrane — context for TM displacement; confirms absolute nm not derivable from this paper alone[see-also]2026-04-25-ren-2002-bm-traveling-wave-pnas — earlier BM wave measurement, same question lineage[see-also]2026-04-25-ghaffari-2007-tm-traveling-wave-pnas — TM-specific dynamics[applies]STRC Piezoelectric TM Bioelectronic Amplifier