Giszter S F, Mussa-Ivaldi F A, Bizzi E
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge 02139-4307.
J Neurosci. 1993 Feb;13(2):467-91. doi: 10.1523/JNEUROSCI.13-02-00467.1993.
Microstimulation of the gray matter of the frog's spinal cord was used to elicit motor responses. Force responses were recorded with the frog's ankle clamped while EMG activity was monitored. The collections of force patterns elicited at different leg configurations were summarized as force fields. These force fields showed convergence to an equilibrium point. The equilibrium paths were calculated from the force fields with the leg clamped. These paths predicted free limb motion in 75% of trials. The force fields were separated into active and prestimulation resting responses. The active force field responses had a fixed position equilibrium. These active force fields were modulated in amplitude over time, although the balance and orientations of forces in the pattern remained fixed. The active fields grouped into a few classes. These included both convergent and parallel fields. The convergent force fields (CFFS) could be observed in deafferented preparations. Motoneuron (MN) activity underlying the force fields was marked using sulforhodamine. The marked activity covered several segments. Several simulations and MN stimulations show that topography, limb geometry, and random activation could not account for the results. It is likely that propriospinal interneurons distribute the activity that underlies the responses observed here. Experiments showed that CFFs that resemble those elicited by microstimulation also underlie natural behaviors. The full variety of fields revealed by microstimulation was larger than the repertoire elicited by cutaneous stimulation. It was concluded that fixed-pattern force fields elicited in the spinal cord may be viewed as movement primitives. These force fields could form building blocks for more complex behaviors.
对青蛙脊髓灰质进行微刺激以引发运动反应。在夹住青蛙脚踝时记录力反应，同时监测肌电图活动。在不同腿部配置下引发的力模式集合被总结为力场。这些力场显示出向平衡点的收敛。在夹住腿部的情况下，根据力场计算出平衡路径。这些路径在75%的试验中预测了自由肢体运动。力场被分为主动和刺激前的静息反应。主动力场反应有一个固定位置的平衡点。这些主动力场的幅度随时间调制，尽管模式中力的平衡和方向保持固定。主动场分为几类。这些包括收敛场和平行场。在去传入神经的标本中可以观察到收敛力场（CFFS）。使用磺基罗丹明标记力场背后的运动神经元（MN）活动。标记的活动覆盖了几个节段。几个模拟和MN刺激表明，地形、肢体几何形状和随机激活无法解释这些结果。很可能脊髓中间神经元分布着此处观察到的反应背后的活动。实验表明，类似于微刺激引发的CFFs也构成自然行为的基础。微刺激揭示的各种场比皮肤刺激引发的全部反应种类更大。得出的结论是，脊髓中引发的固定模式力场可被视为运动原语。这些力场可以构成更复杂行为的构建块。
