Projections of pyramidal tract cells to alpha‐motoneurones innervating hind‐limb muscles in the monkey.
Projections of pyramidal tract cells to alpha‐motoneurones innervating hind‐limb muscles in the monkey.
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锥体束细胞投射到支配猴子后肢肌肉的α运动神经元。
DOI：
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发表时间：
1975
期刊：
影响因子：
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通讯作者：
R. Tanaka
中科院分区：
文献类型：
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作者：
E. Jankowska;Y. Padel;R. Tanaka
1.我们研究了单突触皮质脊髓投射到后肢运动神经元的空间组织，使用中央前回表面的近阈值刺激来激活锥体束（PT）细胞，并使用运动神经元的细胞内记录来检测产生的ep.s.p.s. s。2.单突触eps在所有研究的运动神经元物种中均观察到皮质起源，包括后肢远端和近端肌肉。运动神经元的比例，其中的e.s.p.s.诱发和后者的振幅表明更广泛的皮质投射到运动核的远侧比近侧肌肉，如先前发现的前肢运动神经元。3.单突触eps的皮层区域。诱发的个别运动神经元是非常大的，最常见的3和7毫米2之间。几个运动神经元似乎在运动皮层的后肢分区内有两个或三个独立的区域。4.锥体束细胞投射到支配同一块肌肉的不同运动神经元的部位通常不相同。它们往往只是部分重叠或根本不重叠。5.不同肌肉的锥体束细胞投射到运动核团的位置往往表现出广泛的重叠。当它发生时，给定运动核的各种运动神经元与其他运动核的运动神经元具有共同的皮质投射区，无论是协同肌还是拮抗肌。我们的研究结果进一步证明了皮质投射到运动神经元的区域重叠，并反对投射到不同运动核团的锥体束细胞的马赛克样组织。6.皮层诱发电位的上升时间。表明皮质脊髓束纤维终止于运动神经元上，其距离索马的距离与Ia类传入纤维的距离大致相同。大多数诱发电位的小振幅。因此，由近阈值皮层刺激诱发的E. P. S. P. s表明，皮层起源的单一E. P. S. P. s很小，投射到单个运动神经元的锥体束细胞的密度通常很低，即使在投射区的中心也是如此。7.皮层内刺激的效果取决于刺激强度。当电流为2 - 3 μ A时，通常在一个运动神经元物种或密切的协同者中诱发e. p. s. p. s。电流为5 - 10 μ A，最大的e. p. s. p. s是许多其他运动神经元。腰部皮质脊髓束下行齐射的延迟表明，皮质内刺激间接激活锥体束细胞;因此，这些刺激的影响不能用于指示负责它们的锥体束细胞的位置。
1. We have investigated the spatial organization of monosynaptic corticospinal projections to hind‐limb motoneurones, using near threshold stimulation of the surface of the precentral gyrus to activate pyramidal tract (PT) cells and intracellular recording from motoneurones to detect the resulting e.p.s.p.s. 2. Monosynaptic e.p.s.p.s. of cortical origin were seen in all motoneurone species investigated, those of distal as well as of proximal hind‐limb muscles. The proportion of motoneurones in which the e.s.p.s. were evoked and the amplitudes of the latter indicated a more extensive cortical projection to motor nuclei for distal than for proximal muscles, as previously found for forelimb motoneurones. 3. Cortical areas from which monosynaptic e.p.s.p.s. were evoked in individual motoneurones were remarkably large, most often between 3 and 7 mm2. Several motoneurones appeared to have two or three separate areas within the hind‐limb division of the motor cortex. 4. Areas of location of pyramidal tract cells projecting to various motoneurones innervating one muscle were usually not identical. They overlapped often only partially or did not overlap at all. 5. Areas of location of pyramidal tract cells projecting to motor nuclei for different muscles often showed an extensive overlap. When it occurred, various motoneurones of a given motor nucleus had common cortical projection areas with motoneurones of other motor nuclei, either to synergistic or to antagonistic muscles. Our results give further evidence for overlapping of areas of cortical projections to motoneurones and speak against a mosaic‐like organization of pyramidal tract cells projecting to different motor nuclei. 6. The rise times of cortically evoked e.p.s.p.s. indicate that the corticospinal tract fibres terminate on motoneurones at approximately similar distances from the soma as group Ia afferents. The small amplitudes of the majority of e.p.s.p.s. evoked by near threshold cortical stimulation therefore suggest that unitary e.p.s.p.s of cortical origin are small and that the density of pyramidal tract cells projecting to individual motoneurones is usually low, even in the centrum of projection areas. 7. Effects of intracortical stimulation depended on the stimulus strength. With currents of 2‐3 muA, e.p.s.p.s were usually evoked in one motoneurone species or in close synergists. With currents of 5‐10 muA, largest e.p.s.p.s a number of other motoneurones. Latencies of descending volleys in the lumbar corticospinal tract indicated that intracortical stimuli activated pyramidal tract cells indirectly; the effects of these stimuli could thus not be used to indicate the location of pyramidal tract cells responsible for them.