Hullar Timothy E, Williams Campbell D
Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine, 660 South Euclid Avenue #8115, Saint Louis, MO 63110, USA.
Hear Res. 2006 Mar;213(1-2):17-24. doi: 10.1016/j.heares.2005.11.009. Epub 2006 Jan 24.
The orientations of the semicircular canals determines the response of the canals to head rotations and, in turn, the brain's ability to interpret those motions. The geometry of chinchillas' semicircular canals has never been reported. Volumetric representations of three chinchilla skulls were generated using a microCT scanner. The centroids of each semicircular canal lumen were identified as they passed through the image slices and were regressed to a plane. Unit vectors normal to the plane representing canal orientations were used to calculate angles between canal pairs. Pitch and roll maneuvers required to bring any canal into the horizontal plane for physiologic investigation were calculated. The semicircular canals of the chinchilla were found to be relatively planar. The horizontal canal was found to be oriented 55.0 degrees anteriorly upward. Pairs of ipsilateral chinchilla canals were not orthogonal and contralateral synergistic pairs were not parallel. Despite this arrangement, the canal plane unit normal vectors were organized to respond with approximately equal overall sensitivity to rotations in any direction. The non-orthogonal chinchilla labyrinth may provide an opportunity to determine whether the frame of reference used by the central vestibular and oculomotor system is based on directions of afferent maximum sensitivity or prime directions.
半规管的方向决定了半规管对头部旋转的反应，进而决定了大脑解释这些运动的能力。关于龙猫半规管的几何形状从未有过报道。使用微型计算机断层扫描仪生成了三个龙猫头骨的体积表示。在每个半规管腔穿过图像切片时确定其质心，并将其回归到一个平面。使用垂直于表示半规管方向的平面的单位向量来计算半规管对之间的角度。计算了将任何半规管置于水平面进行生理研究所需的俯仰和滚动动作。发现龙猫的半规管相对呈平面状。发现水平半规管向前上方倾斜55.0度。同侧龙猫半规管对不正交，对侧协同对不平行。尽管有这种排列，但半规管平面单位法向量的组织方式是对任何方向的旋转都具有大致相等的总体敏感性。龙猫迷宫的非正交性可能为确定前庭中枢和动眼系统所使用的参考系是基于传入最大敏感性方向还是主要方向提供了机会。
