Characterizing the primary resonator in the cochlea

Abstract

The cochlear traveling waves are explained by a bank of independent resonators coupled longitudinally by lymphatic fluids. Many cochlear models require at least two resonators to account for observed responses. To investigate the resonators in the cochlea, we used high-resolution optical coherence tomography to measure 2-D vibration patterns of the organ of Corti in acutely excised cochleae from young Mongolian gerbils. The excised tissues were acoustically stimulated. The transverse and radial vibrations of the basilar membrane (BM) and the tectorial membrane (TM) were obtained over their radial span. The BM vibrated from the primary to a higher mode transversely as the stimulating frequency increased. The higher-order mode appeared near the best frequency (BF) of the measured location. Meanwhile, the TM showed no sign of a mode transition up to 1 octave above the BF in radial or transverse vibrating patterns. Within the physiological frequency range, the BM exhibits the characteristic behavior of a resonator. In contrast, the TM does not. Our results suggest that the TM as the second resonator is not the universal mechanism across the entire cochlea.