Armstrong D M, Drew T
J Physiol. 1985 Oct;367:309-26. doi: 10.1113/jphysiol.1985.sp015826.
Chronically implanted microwires were used to deliver brief trains of electrical stimuli (11 cathodal pulses at 330 Hz and intensity 5-35 microA) to sixty-two locations in the grey matter of the pericruciate cortex in cats. Electromyographic (e.m.g.) responses in the contralateral forelimb were recorded from a total of ten muscles (four to eight in each animal) acting about the shoulder, elbow and wrist and on the digits. The animals were relaxed with little background e.m.g. in the muscles and as a result only excitatory effects could be described. Five muscles which are flexors in the locomotor context were excited from more electrodes, distributed more widely across the motor cortex, than another five muscles which are extensors during locomotion; this difference in 'accessibility' was present both at 35 microA stimulus intensity and at 15 microA. At a stimulus intensity of 15 microA, effective cortical electrodes tended to cluster either in the most lateral part of the anterior sigmoid gyrus (rostromedial focus) or in the coronal gyrus just caudal to a line prolonged beyond the lateral end of the cruciate sulcus (caudolateral focus). This is consistent with the existence of a double motor representation within the forelimb motor cortex (Pappas & Strick, 1981). The two foci were similar in that both gave rise to more flexor than extensor responses and to fewer responses in digit or wrist muscles than in muscles acting about more proximal joints (elbow and shoulder). At stimulus intensity 35 microA the latency of the earliest e.m.g. responses ranged from 11 to 14 ms in different muscles. For some muscles and electrodes the amplitude of the e.m.g. responses was substantially altered by a quite small postural change. After pyramidectomy the cortical thresholds and the e.m.g. latencies were both greatly increased.
长期植入的微丝被用于向猫的十字周皮层灰质中的62个位置传递短暂的电刺激序列（330赫兹、强度为5 - 35微安的11个阴极脉冲）。从总共10块肌肉（每只动物4 - 8块）记录对侧前肢的肌电图（e.m.g.）反应，这些肌肉作用于肩部、肘部、腕部以及手指。动物处于放松状态，肌肉中的背景肌电图活动很少，因此只能描述兴奋效应。在运动情境中为屈肌的5块肌肉比另外5块在运动中为伸肌的肌肉，从更多电极得到兴奋，且这些电极在运动皮层上分布更广泛；这种“可及性”差异在35微安刺激强度和15微安时均存在。在15微安的刺激强度下，有效的皮层电极倾向于聚集在前乙状回最外侧部分（嘴内侧焦点）或冠状回中，该冠状回恰好在一条延长线超出十字沟外侧端的尾侧（尾外侧焦点）。这与在前肢运动皮层内存在双重运动表征一致（帕帕斯和斯特里克，1981）。这两个焦点的相似之处在于，两者产生的屈肌反应都多于伸肌反应，且手指或腕部肌肉的反应少于作用于更近端关节（肘部和肩部）的肌肉。在35微安刺激强度下，不同肌肉中最早的肌电图反应潜伏期在11至14毫秒之间。对于一些肌肉和电极，相当小的姿势变化会使肌电图反应的幅度发生显著改变。在进行锥体切除术后，皮层阈值和肌电图潜伏期都大幅增加。
