Three-dimensional extraocular motoneuron innervation in the rhesus monkey. I: Muscle rotation axes and on-directions during fixation.

摘要: The rotation axis for each of the six extraocular muscles was determined in four eyes from three perfused rhesus monkeys. Measurements locations muscle insertions and origins were made stereotaxic reference frame with x-y plane horizontal x-z sagittal. computed axes recti close to being at an angle about 15° z axis. vertical obliques 30° y In five alert monkeys, we simultaneously recorded motoneuron activity eye position dimensions (3D). 51 axons obtained oculomotor (n=34), trochlear (n=11), abducens nerve (n=6) during spontaneous movements. To extend torsional range position, animals also put different static roll positions, which induced ocular counterroll without dynamic vestibular stimulation. Periods 100 ms fixation or slow movements (<10°/s) chosen analysis. For motoneuron, a multiple linear regression performed between firing frequency 3D expressed as vector, both Listing’s frame. direction highest correlation coefficient (average R=0.94±0.07 SD) taken on-direction. Each unit’s could be unequivocally attributed one particular muscle. On-directions confined well-defined cone 3D. Average on-directions motoneurons differed significantly corresponding anatomically (range deviations: 11.9° 29.0°). This difference most pronounced oblique muscles. rectus pair form 58.3°, whereas paired 105.6°. better aligned semicircular canal afferents deviation: 9.4–18.9°) sensitivity vectors canals 3.9–15.9°) than axes, but significant differences remain explained. arranged symmetrically plane, sense that components antagonistically almost equal, opposite sign. Thus, cancel when are plane. arrangement simplifies neuronal transformations conjugate head-fixed voluntary movements, while approximate alignment is optimal generating compensatory