Dickman J D
Department of Surgery (Otolaryngology), University of Mississippi Medical Center, Jackson 39216, USA.
Exp Brain Res. 1996 Sep;111(1):8-20. doi: 10.1007/BF00229550.
Rotational head motion in vertebrates is detected by the semicircular canal system, whose innervating primary afferent fibers carry information about movement in specific head planes. The semicircular canals have been qualitatively examined over a number of years, and the canal planes have been quantitatively characterized in several animal species. The present study first determined the geometric relationship between individual semicircular canals and between the canals and the stereotactic head planes in pigeons. Stereotactic measurements of multiple points along the circumference of the bony canals were taken, and the measured points fitted with a three-dimensional planar surface. Direction normals to the plane's surface were calculated and used to define angles between semicircular canal pairs. Because of the unusual shape of the anterior semicircular canals in pigeons, two planes, a major and a minor, were fitted to the canal's course. Calculated angle values for all canals indicated that the horizontal and posterior semicircular canals are nearly orthogonal, but the anterior canals have substantial deviations from orthogonality with other canal planes. Next, the responses of the afferent fibers that innervate each of the semicircular canals to 0.5 Hz sinusoidal rotation about an earth-vertical axis were obtained. The head orientation relative to the rotation axis was systematically varied so that directions of maximum sensitivity for each canal afferent could be determined. These sensitivity vectors were then compared with the canal plane direction normals. The afferents that innervated specific semicircular canals formed homogeneous clusters of sensitivity vectors in different head planes. The horizontal and posterior afferents had average sensitivity vectors that were largely co-incident with the innervated canal plane direction normals. Anterior canal afferents, however, appeared to synthesize contributions from the major and minor plane components of the bony canal structure to produce a resultant sensitivity vector that was positioned between the canal planes. Calculated angles between the average canal afferent sensitivity vectors revealed that direction orthogonality is preserved at the afferent signal level, even though deviations from canal plane orthogonality exist.
脊椎动物头部的旋转运动由半规管系统检测，其支配的初级传入纤维携带有关特定头部平面运动的信息。多年来，人们对半规管进行了定性研究，并且已经对几种动物物种的半规管平面进行了定量表征。本研究首先确定了鸽子个体半规管之间以及半规管与立体定向头部平面之间的几何关系。对骨半规管圆周上的多个点进行立体定向测量，并将测量点拟合到三维平面上。计算该平面表面的方向法线，并用于定义半规管对之间的角度。由于鸽子前半规管的形状异常，因此用一个主平面和一个次平面拟合该半规管的走向。所有半规管的计算角度值表明，水平半规管和后半规管几乎正交，但前半规管与其他半规管平面存在明显的非正交偏差。接下来，获得了支配每个半规管的传入纤维对绕地球垂直轴以0.5Hz正弦旋转的响应。系统地改变头部相对于旋转轴的方向，以便确定每个半规管传入纤维的最大敏感方向。然后将这些敏感向量与半规管平面方向法线进行比较。支配特定半规管的传入纤维在不同头部平面上形成了敏感向量的同质簇。水平和后半规管传入纤维的平均敏感向量在很大程度上与所支配的半规管平面方向法线重合。然而，前半规管传入纤维似乎综合了骨半规管结构的主平面和次平面成分的贡献，以产生一个位于半规管平面之间的合成敏感向量。计算得出的平均半规管传入纤维敏感向量之间的角度表明，即使存在半规管平面非正交性偏差，在传入信号水平上方向正交性仍然得以保留。
