Graf W, de Waele C, Vidal P P, Wang D H, Evinger C
Rockefeller University, New York, NY., USA.
Brain Behav Evol. 1995;45(4):209-31. doi: 10.1159/000113551.
Previously we demonstrated a stereotyped resting posture of the head-neck arrangement in a number of vertebrates: the cervical vertebral column is oriented vertically to form one portion of the partial S-shaped configuration of the entire spine. The present investigation quantified the various strategies of head-neck movements employed by different mammalian species (human, monkeys, cats, rabbits and guinea pigs) using cineradiography. At rest, bipeds and quadrupeds hold their heads at the extreme point of flexion of the passive atlanto-occipital range of motion. In this posture, the horizontal semicircular canals are tilted upward from earth horizontal by 5 to 10 degrees and roughly parallel the plane determined by the two obliquus capitis posterior muscles. Furthermore, at this head position, the utricular maculae become oriented earth-horizontally. In quadrupedal animals, head-neck movements in the sagittal plane result from movement at the atlanto-occipital articulation (head/C1) and at the multi-articular cervico-thoracic junction (C6-Th3). Only very small flexion/extension movements occur within the body of the cervical vertebral column (C2-C5). Lowering the head from the resting position is only possible by flexion at the C6-Th3 vertebrae. Raising of gaze from the resting position is only possible by extension of the head at the atlanto-occipital articulation. By contrast, sagittal plane head movements in bipeds are largely confined to the cervico-thoracic junction. This is related to a significantly reduced range of motion of the atlanto-occipital articulation. In monkeys and humans, it range of motion is about 13 and 8-11 degrees, respectively, compared to 105 degrees in rabbits. Our cineradiographic data demonstrated different strategies for head movements in the sagittal plane between quadrupeds and bipeds. At one end of the spectrum, in the case of rabbits, there was no systematic relationship between head and neck orientation. Rabbits stabilized head posture by using the head-neck structure in a parallelogram fashion, which resulted in head posture being largely independent of cervical vertebral column orientation. In monkeys and humans, however, orientation of the head depended almost entirely on the orientation of the cervical vertebral column. In such case, head movements in the sagittal plane almost exclusively relied on the positioning of the cervico-thoracic junction. These different strategies again correlate with the different ranges of motion of the atlanto-occipital articulation. We suggest that vertebrates use mechanical constraints and preferred planes of action for head-neck movement control to simplify sensory-motor transformations subserving motor control and plasticity and to minimize neuronal operations.
此前我们证明了许多脊椎动物头部 - 颈部排列的一种固定静止姿势：颈椎垂直定向，形成整个脊柱部分S形构型的一部分。本研究使用X线电影摄影术量化了不同哺乳动物物种（人类、猴子、猫、兔子和豚鼠）采用的头部 - 颈部运动的各种策略。在静止时，两足动物和四足动物将头部保持在被动寰枕运动范围内的屈曲极限点。在这种姿势下，水平半规管从地球水平向上倾斜5至10度，大致平行于由两条头后斜肌确定的平面。此外，在这个头部位置，椭圆囊斑呈地球水平方向排列。在四足动物中，矢状面内的头部 - 颈部运动源于寰枕关节（头部/C1）和多关节颈胸交界处（C6 - Th3）的运动。颈椎椎体（C2 - C5）主体内仅发生非常小的屈伸运动。只有通过C6 - Th3椎体的屈曲才能使头部从静止位置降低。只有通过寰枕关节处头部的伸展才能使视线从静止位置抬高。相比之下，两足动物矢状面内的头部运动主要局限于颈胸交界处。这与寰枕关节的运动范围显著减小有关。在猴子和人类中，其运动范围分别约为13度和8 - 11度，而兔子为105度。我们的X线电影摄影数据证明了四足动物和两足动物在矢状面内头部运动的不同策略。在一个极端情况下，就兔子而言，头部和颈部的方向之间没有系统的关系。兔子以平行四边形方式利用头部 - 颈部结构稳定头部姿势，这导致头部姿势在很大程度上独立于颈椎的方向。然而，在猴子和人类中，头部的方向几乎完全取决于颈椎的方向。在这种情况下，矢状面内的头部运动几乎完全依赖于颈胸交界处的定位。这些不同的策略再次与寰枕关节的不同运动范围相关。我们认为脊椎动物利用机械约束和头部 - 颈部运动控制的首选作用平面来简化服务于运动控制和可塑性的感觉 - 运动转换，并使神经元操作最小化。
