Fig. 7
From: Vibration hotspots reveal longitudinal funneling of sound-evoked motion in the mammalian cochlea
Frequency-dependent spatial profiles of a vibration hotspot. a Transverse anatomical schematic for the 23 kHz region of the gerbil cochlea (cf. Fig. 2a), illustrating the spatial pathway (red arrow) across which vibration amplitude (b) and phase (c) were analyzed. The white star marks the reference point on the BM; the black triangle the middle of the outer hair cell region. b, c Spatial profiles of vibration amplitude and phase for 21 different frequency components (color-coded) in a multi-tone stimulus. The curves for five frequencies (indicated in c) are highlighted by increased line width. Amplitudes and phases are expressed relative to those observed on the BM (cf. white star in a). Gray patches indicate the different regions traversed by the red arrow, including the BM, Deiters’ cells (DC), and OHCs. d Schematized anatomical relationship between Deiters’ cells (yellow) and OHCs (blue) along the longitudinal axis of the cochlea, perpendicular to the section shown in a. The cells are shown suspended between BM and RL, with the OHC stereocilia protruding downwards (beneath the level of the RL). The apical-ward projection of the Deiters’ cells soma and phalangeal processes contrasts with the basal-ward projection of the OHC43, 51. e Measured vibration profile for the 5-kHz data of b, recast onto linear coordinates, for comparison with the cartoon in f. f A hypothetical interpretation of the profile from e, based on the idea that motion in the OHC/Deiters’ cell hotspot is primarily oriented in the longitudinal direction (see text). Two snapshots of a single OHC/Deiters’ cell “unit” are shown, one in gray and the other in colors (blue, OHC; yellow, DC). The snapshots depict the unit at the two extremes of an elliptical vibration cycle. The illustrated movement is highly exaggerated: the measured 2.8-nm maximum displacement is scaled up 1000-fold, relative to the scale of the cellular anatomy, to make it visible in the illustration. Data were obtained from the same preparation as in Figs. 2, 3, CF 23 kHz. Stimulus level 50 dB SPL
