Rabbitt R D
Department of Bioengineering, University of Utah Salt Lake City 84112, USA.
Biol Cybern. 1999 Jun;80(6):417-31. doi: 10.1007/s004220050536.
A morphologically descriptive mathematical model was developed to study the role of labyrinthine geometry in determining sensitivities of each semicircular canal to angular motion stimuli in three-dimensional (3D) space. For this, equations describing viscous flow of the endolymph and poro-elastic response of the cupulae were coupled together and solved within a 3D reconstructed geometry. Results predict the existence of prime rotational directions about which the labyrinth resolves 3D angular movements into separate vectorial components. The components are predicted to be transmitted to the brain separately, one coded by each canal nerve. Prime directions predicted by the model are non-orthogonal, distinct from the anatomical canal planes, and distinct from the directions of rotation which elicit maximal responses of individual canal nerves. They occur for each canal along the intersection of the two null planes defined by its sister canals. Hence, rotation about a prime direction excites only one canal nerve. This contrasts the situation for rotations about anatomical canal planes, or about maximal response directions, where the model predicts activation of multiple canal nerves. The prime directions are sensitive to labyrinthine morphology and, hence, are predicted to vary between species and, to a lesser extent, vary between individual animals. Prime directions were estimated in the present work using a mathematical model, but could be determined experimentally based on the directional sensitivities of individual canal nerves. The model also predicts the existence of dominant eigenmodes and time constants associated with rotation in each of the prime directions. Results may have implications regarding the central representation of angular head movements in space as well as the neuronal mappings between three-canal afferent inputs and motor outputs.
开发了一种形态学描述性数学模型，以研究内耳迷路几何结构在确定每个半规管对三维（3D）空间中角运动刺激的敏感性方面的作用。为此，将描述内淋巴粘性流动和壶腹孔隙弹性响应的方程耦合在一起，并在三维重建几何结构中求解。结果预测了主要旋转方向的存在，内耳迷路围绕该方向将三维角运动分解为单独的矢量分量。这些分量预计会分别传递到大脑，每条半规管神经编码一个分量。该模型预测的主要方向是非正交的，不同于解剖学半规管平面，也不同于引发单个半规管神经最大反应的旋转方向。它们沿着由其对侧半规管定义的两个零平面的交线出现在每个半规管中。因此，围绕主要方向的旋转仅刺激一条半规管神经。这与围绕解剖学半规管平面或最大反应方向的旋转情况形成对比，在这种情况下，模型预测会激活多条半规管神经。主要方向对内耳迷路形态敏感，因此预计在不同物种之间会有所不同，在个体动物之间也会有较小程度的差异。在本研究中，主要方向是使用数学模型估计的，但也可以根据单个半规管神经的方向敏感性通过实验确定。该模型还预测了与每个主要方向的旋转相关的主导本征模式和时间常数的存在。这些结果可能对视空间中角头部运动的中枢表征以及三半规管传入输入和运动输出之间的神经元映射有影响。
