Role of Presynaptic inhibition for controlling vilitional movement

我们检测了执行腕关节屈伸任务的猴子的初级传入去极化（PAD）的调制。刺激桡浅神经（SR）和桡深神经（DR），记录脊髓[C6-T1]内单个INs和局部场电位（LFP）的诱发反应。当观察到单突触反应时，通过记录微电极连续施加微刺激（1-20μA：3- 10 Hz），并通过三极袖状电极记录SR中的逆向齐射（AV）。单一刺激有时诱发多个（2-8）AV，可能是通过激活不同传导速度的传入末梢。我们计算了单个截击的大小（面积）（n=270），并在每个行为时期（休息，提示，延迟，运动，保持等）取平均值。至于SR，大多数截击的大小（58%）增加或减少显着相对于控制期的特定阶段的行为任务，表明PAD调制在一个任务依赖的方式。显示调制的AV比未调制的AV具有更快的传导速度（57.04 ± 13.04 vs. 53.20 ± 13.65，p<0.01），表明PAD调制的主要目标可能是更快的传导纤维（即A-β）。许多截击的大小增加在积极的手腕运动对弹性负荷，当单突触单位的反应和LFPs下降。这些数据表明，低阈值皮肤输入可以通过行为相关的方式改变PAD的量来调节突触前（图3）。在DR神经中也获得了类似的结果。

we examined the modulation of primary afferent depolarization (PAD) in monkeys performing a wrist flexion-extension task. We stimulated the superficial radial (SR) and Deep radial (DR) nerve and recorded evoked responses of single INs and local field potentials (LFP) in spinal cord [C6-T1]. When a monosynaptic response was observed, we delivered micro stimuli (1-20μA: 3-10Hz) continuously through the recording microelectrode and recorded antidromic volleys (AVs) in the SR through a tripolar cuff electrode. Single stimuli sometimes evoked multiple (2-8) AVs, possibly by activating afferent terminals with different conduction velocity. We calculated the size (area) of individual volleys (n=270) and averaged in each behavioral epoch[rest, cue, delay, movement, hold, etc]. As for SR, the size of most volleys (58%) increased or decreased significantly relative to control period in specific phases of the behavioral task, indicating that PAD was modulated in a task-dependent manner. AVs showing modulation had faster conduction velocities than those without modulation (57.04+-13.04 vs. 53.20+-13.65, p<0.01), suggesting the primary target of PAD modulation could be faster conducting fibers (i.e. A-beta). The size of many volleys increased during active wrist movement against an elastic load, when monosynaptic unit responses and LFPs decreased. These data suggest that low-threshold cutaneous input can be modulated presynaptically by changing the amount of PAD in a behaviorally relevant way (Fig.3). Comparable result was also obtained in the DR nerve.