POSTSPIKE FACILITATION OF FORELIMB MUSCLE-ACTIVITY BY PRIMATE CORTICOMOTONEURONAL CELLS
POSTSPIKE FACILITATION OF FORELIMB MUSCLE-ACTIVITY BY PRIMATE CORTICOMOTONEURONAL CELLS
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DOI：
10.1152/jn.1980.44.4.751
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发表时间：
1980-01-01
影响因子：
2.5
通讯作者：
CHENEY, PD
中科院分区：
文献类型：
--
作者：
FETZ, EE;CHENEY, PD
在猕猴对抗弹性负载时进行斜坡和保持手腕运动时，记录了与任务相关的运动皮层细胞以及特定手腕和手指肌肉的活动。 EMG [肌电图] 电极对植入 6 块屈肌和 6 块伸肌中。对于在手腕运动期间放电的中央前皮层细胞，编制了 5-6 个共激活肌肉的全波校正 EMG 活动的尖峰触发平均值 (STA)。在由选定细胞编译的 STA 中，18% 显示出平均 EMG 活动的尖峰后促进 (PSF) 的证据。这种 PSF 在皮质尖峰达到峰值后开始，并再次下降至尖峰前基线水平。 78% 的 STA 没有表现出与尖峰相关的特征，4% 的 STA 表现出复杂的特征。量化时，强 PSF 相对于平均基线水平和最大基线波动具有最大的峰值幅度。强 PSF 比中度或弱 PSF 具有稍短的起始潜伏期和较长的持续时间。快速锥体束神经元（PTN）主要产生起始潜伏期最短的 PSF，但也产生潜伏期较长的 PSF；慢速 PTN 产生具有较长延迟的 PSF。具有短暂峰间间隔的峰对对产生 PSF 特别有效。由非常短的峰间间隔分开的 2 个动作电位触发的 STA 显示出超过孤立动作电位 PSF 线性和的净促进作用。大多数细胞在超过 1 个共激活的前肢肌肉中产生 PSF。为了消除通过不同电极对相同促进运动单位进行冗余记录的任何可能性，肌电图活动是相互关联的，并且那些具有显着串扰证据的记录被排除在数据库之外。在 5-6 块独立肌肉记录的 370 个任务相关神经元中，27% 的至少 1 块肌肉产生强或中度 PSF。其中一半在超过 1 块肌肉中产生了透明的 PSF。细胞的肌场，即一组促进肌肉，通常包含共激活的增效肌的子集。伸肌细胞的促进肌肉平均数量为 2.5 个，屈肌细胞为 2.1 个。对前肢伸肌的兴奋作用往往比对屈肌的兴奋作用更强、更广泛。显示清晰 PSF 的任务相关细胞比例，伸肌细胞 (37%) 大于屈肌细胞 (22%)。伸肌细胞 (1.2) 的强 PSF 与弱 PSF 的比率是屈肌细胞 (0.6) 的两倍。手指伸肌比腕伸肌或屈肌更容易促进。大多数 PSF 的强度、潜伏期和时间过程表明它们是由单突触皮质运动神经元 (CM) 连接介导的，尽管不能排除通过间接连接的贡献。以强和中等 PSF 作为 CM 连接的证据，CM 细胞显然通常将不同的末端分布到超过 1 个肌肉的运动神经元。伸肌细胞较大的肌区可能反映出比屈肌细胞更大的末端分歧。
In macaques making ramp-and-hold wrist movements against elastic loads, the activity of task-related motor cortex cells and specific wrist and finger muscles was recorded. EMG [electromyograph] electrode pairs were implanted in 6 flexor and 6 extensor muscles. For precentral cortex cells that discharged during the wrist movements spike-triggered averages (STA) of full-wave rectified EMG activity of 5-6 coactivated muscles were compiled. Of this STA compiled from selected cells 18% showed evidence of postspike facilitation (PSF) of average EMG activity. Such PSF began after the cortical spike reached a peak and declined again to prespike baseline levels. Of the STA 78% showed no spike-related features, and 4% exhibited complex features. When quantified, strong PSF had the largest peak amplitudes relative to mean base-line levels and relative to maximal base-line fluctations. Strong PSF had slightly shorter onset latency and longer duration than moderate or weak PSF. Fast pyramidal tract neurons (PTN) produced mainly PSF with the shortest onset latencies, but also gave rise to PSF with longer latencies; slow PTN produced PSF with longer latencies. Pairs of spikes with brief interspike intervals were particularly effective in generating PSF. STA triggered from 2 action potentials separated by very short interspike intervals showed a net facilitation exceeding the linear sum of the PSF of isolated action potentials. Most cells produced PSF in more than 1 of the coactivated forelimb muscles. To eliminate any possibility of redundant recording of the same facilitated motor units through different electrodes, EMG activity was cross-correlated and those records with evidence of significant cross talk were excluded from the data base. Of 370 task-related neurons recorded with 5-6 independent muscles, 27% produced strong or moderate PSF in at least 1 muscle. Half of these produced clear PSF in more than 1 muscle. The cell''s muscle field, i.e., the set of facilitated muscles, typically comprised a subset of the coactivated synergist muscles. The mean number of facilitated muscles was 2.5 for extensor cells and 2.1 for flexor cells. The excitatory effects on forelimb extensor muscles tended to be stronger and more widespread than on flexor muscles. The proportion of task-related cells showing clear PSF was larger for extensor cells (37%) than flexor cells (22%). The ratio of strong to weak PSF was twice as great for extensor cells (1.2) as for flexor cells (0.6). Finger extensor muscles were more strongly facilitated than wrist extensor muscles or flexor muscles. The strength, latency and time course of most PSF suggest they are mediated by monosynaptic corticomotoneuronal (CM) connections, although a contribution through indirect linkages cannot be excluded. Taking the strong and moderate PSF as evidence of CM connections, CM cells apparently commonly distribute divergent terminals to motoneurons of more than 1 muscle. The larger muscle fields of extensor cells may reflect a greater divergence of terminals than flexor cells.