Department of Biomedical and Clinical Sciences, Linköping University, 58185, Linköping, Sweden.
Sci Rep. 2021 Feb 3;11(1):2855. doi: 10.1038/s41598-021-82268-3.
Sound and vibrations that cause the skull bone to vibrate can be heard as ordinary sounds and this is termed hearing by bone conduction (BC). Not all mechanisms that causes a skull vibration to result in BC hearing are known, and one such unknown is how the direction of the vibration influences BC hearing. This direction sensitivity was investigated by providing BC stimulation in five different directions at the vertex of the guinea pig skull. The hearing thresholds for BC stimulation was obtained in the frequency range of 2 to 20 kHz by measurements of compound action potential. During the stimulation by BC, the vibration of the cochlear promontory was measured with a three-dimensional laser Doppler vibrometer resulting in a set of unique three-dimensional velocity magnitude combinations for each threshold estimation. The sets of three-dimensional velocity magnitude at threshold were used to investigate nine different predictors of BC hearing based on cochlear promontory velocity magnitudes, six single direction (x, y and z directions in isolation, the normal to the stapes footplate, the oval to round window direction, and the cochlear base to apex direction), one linear combination of the three dimension velocity magnitudes, one square-rooted sum of the squared velocity magnitudes, and one sum of the weighted three dimensional velocity magnitudes based on a restricted minimum square error (MSE) estimation. The MSE gave the best predictions of the hearing threshold based on the cochlear promontory velocity magnitudes while using only a single direction gave the worst predictions of the hearing thresholds overall. According to the MSE estimation, at frequencies up to 8 kHz the vibration direction between the right and left side gave the greatest contribution to BC hearing in the guinea pig while at the highest frequencies measured, 16 and 20 kHz, the anteroposterior direction of the guinea pig head gave the greatest contribution.
引起颅骨骨振动的声音和振动可以被听到，这被称为骨传导（BC）听力。并非所有导致颅骨振动导致 BC 听力的机制都已知，其中一个未知的机制是振动方向如何影响 BC 听力。通过在豚鼠颅骨顶点以五个不同方向提供 BC 刺激来研究这种方向敏感性。通过测量复合动作电位，在 2 到 20 kHz 的频率范围内获得了 BC 刺激的听力阈值。在 BC 刺激期间，用三维激光多普勒测振仪测量了耳蜗穹窿的振动，从而为每个阈值估计得出了一组独特的三维速度幅度组合。在阈值处的三维速度幅度组用于研究基于耳蜗穹窿速度幅度的九个不同的 BC 听力预测因子，六个单方向（x、y 和 z 方向单独，镫骨足板的法向，卵圆窗到圆窗方向，以及耳蜗基底到顶点方向），一个三维速度幅度的线性组合，一个平方速度幅度的平方根和一个基于受限最小均方误差（MSE）估计的加权三维速度幅度的和。MSE 基于耳蜗穹窿速度幅度对听力阈值的预测最佳，而仅使用一个方向对听力阈值的预测最差。根据 MSE 估计，在高达 8 kHz 的频率下，豚鼠右侧和左侧之间的振动方向对 BC 听力的贡献最大，而在测量的最高频率 16 和 20 kHz 下，豚鼠头部的前后方向对 BC 听力的贡献最大。
