Gueta et al. 2008 — Sound-evoked deflections of OHC stereocilia arise from TM anisotropy
CORRECTION FLAG: The STRC topic file cites this paper as “Gueta R et al. (2008) Biophys J 95:4948.” The correct citation is Biophys J 94(11):4570–4576 — the volume is 94, not 95, and pages are 4570-4576. This paper is also misidentified in the topic file as potentially reporting absolute TM displacement values (“Gueta 2006, Ren 2011” is cited for 5–30 nm TM displacement). Gueta 2008 does NOT report absolute displacement in nm — it reports TM material anisotropy and FEM modeling of stereocilia deflection angles.
TL;DR. Force spectroscopy on mouse TM shows vertical Young’s modulus ~300 kPa, lateral moduli Ex = 45 kPa and Ey = 75 kPa (4–6× anisotropy). FEM simulations show this anisotropy causes stereocilia to deflect laterally rather than penetrate TM vertically during acoustic stimulation — a fundamental hearing mechanism.
Key finding. The TM’s anisotropic stiffness (vertical >> lateral) is the mechanical reason stereocilia deflect rather than buckle. The degree of lateral deflection increases proportionally with vertical displacement when anisotropic properties are applied. This paper does NOT provide the 5–30 nm displacement values cited in the h02 scripts under “Gueta 2006.”
Numbers that matter
| Parameter | Value | Units | Source location | Conditions |
|---|---|---|---|---|
| TM vertical Young’s modulus (normal) | 300 | kPa | Results, force spectroscopy | Mouse TM, AFM force spectroscopy |
| TM lateral modulus Ex | 45 | kPa | Results, FEM fit | Anisotropic model |
| TM lateral modulus Ey | 75 | kPa | Results, FEM fit | Anisotropic model |
| Vertical:lateral anisotropy ratio | 4–6 | × | Results | Vertical ÷ lateral stiffness |
| PDMS control: vertical stiffness | 420 | kPa | Results | Isotropic control material |
| PDMS control: lateral stiffness | 700 | kPa | Results | Ratio 1.7× — near isotropic |
| Absolute stereocilia displacement reported | none | — | — | Only deflection angles in FEM; no nm values |
On TM displacement citations in h02 scripts. The values “30 nm (200 Hz), 20 nm (1 kHz), 10 nm (4 kHz), 5 nm (8 kHz) at 60 dB SPL” cited as “Gueta 2006, Ren 2011” do not originate from this paper (Gueta 2008). “Gueta 2006” may be a misremembered citation — this author’s publication record has no 2006 cochlear mechanics paper by this name. The 5–30 nm range is broadly consistent with in-vivo OCT measurements (Gao et al. 2014) but the script citations are not traceable to Gueta 2008.
Limitations
- Static AFM force spectroscopy; TM is viscoelastic so dynamic stiffness differs.
- Mouse TM ex vivo; attachment constraints in vivo alter effective stiffness.
- Anisotropy values depend heavily on model assumptions in FEM.
Connections
[source]tectorial-membrane — corrects volume/page (94:4570 not 95:4948); clarifies this paper does NOT report absolute nm displacements[see-also]2026-04-25-ghaffari-2007-tm-traveling-wave-pnas — dynamic G′ measurements, complementary[see-also]2026-04-25-gavara-2009-tm-collagen-anisotropy-afm — fiber-level anisotropy origin[see-also]2026-04-25-gao-2014-organ-corti-oct-vibration — actual OCT displacement measurements[applies]STRC Piezoelectric TM Bioelectronic Amplifier