Gavara & Chadwick 2009 — Collagen-based mechanical anisotropy of the tectorial membrane
CORRECTION FLAG: This paper is the actual source of PLoS One 4:e4877. The STRC topic file cited it as “Masaki K et al. 2009 PLOS One 4:e4877” — the authors are wrong. The correct authors are Núria Gavara and Richard S. Chadwick (NIH/NIDCD Auditory Mechanics Section). The 24–210 kPa Young’s modulus values attributed to “Masaki 2009” require separate sourcing — Gavara & Chadwick report fiber modulus ~1 kPa (order of magnitude), not 24–210 kPa.
TL;DR. Gavara & Chadwick used AFM combined with optical tracking and an anisotropic elastic model to extract three independent TM elastic moduli. Fiber modulus Ef ≈ 1 kPa (base) with smaller apex values; shear moduli an order of magnitude smaller (~0.1 kPa). Large mechanical anisotropy transmits deformation preferentially along the direction that excites OHC bundles, while blocking perpendicular transmission.
Key finding. TM anisotropy is collagen-fiber-mediated: radial fibers (~1 µm diameter at base, ~0.4 µm at apex) create direction-dependent stiffness. All moduli are larger at base than apex. The effective Young’s modulus E from this model reproduces qualitatively the base-to-apex gradient observed in other studies — but Gavara 2009 reports E in the kPa range, consistent with the order of magnitude, not 24–210 kPa as attributed to “Masaki 2009” in the h02 audit.
Numbers that matter
| Parameter | Value | Units | Source location | Conditions |
|---|---|---|---|---|
| Fiber modulus Ef (base) | ~1 | kPa | Table 1 / Results | Mouse TM, AFM + optical tracking |
| Fiber modulus Ef (apex) | < 1 | kPa | Table 1 | Smaller than base |
| Shear moduli μL, μT | ~0.1 | kPa | Results | Order of magnitude smaller than Ef |
| All moduli gradient | base > apex | — | Results | Qualitative; all moduli follow gradient |
| Radial collagen fiber diameter (base) | ~1 | µm | Figure 6 | AFM imaging |
| Radial collagen fiber diameter (apex) | ~0.4 | µm | Figure 6 | Thinner at apex |
| Fiber periodicity gap (base) | 0.6 | µm | Figure 6 | Between fibers |
| Fiber periodicity gap (apex) | 0.75 | µm | Figure 6 | Wider spacing at apex |
| AFM indentation depth | 1 (initial) + 1 | µm | Methods | Force 10–120 nN range |
On the 24 kPa / 210 kPa claim: These values do NOT appear to come from Gavara & Chadwick 2009 (which reports moduli in the ~1 kPa fiber modulus range). The 24–210 kPa range for TM Young’s modulus is likely from a different source — possibly Shoelson et al. (2004 Biophys J) or a later AFM study. The h02 topic file’s attribution of “24 kPa apical, 210 kPa basal” requires additional sourcing beyond this paper.
Limitations
- Model assumes transversely isotropic material; TM may have more complex symmetry.
- Ex vivo preparation; ionic conditions and temperature affect hydrogel stiffness.
- Absolute moduli values model-dependent; different constitutive assumptions shift values.
Connections
[source]tectorial-membrane — corrects citation: actual PLoS One 4:e4877 paper; fiber modulus ~1 kPa not 24 kPa[see-also]2026-04-25-masaki-2009-tm-col11a2-anisotropy — complementary: molecular origin of anisotropy[see-also]2026-04-25-ghaffari-2007-tm-traveling-wave-pnas — dynamic G′ measurements, same lab[applies]STRC Piezoelectric TM Bioelectronic Amplifier