Contributions of the reticulospinal system to the postural adjustments occurring during voluntary gait modifications
Contributions of the reticulospinal system to the postural adjustments occurring during voluntary gait modifications
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DOI：
10.1152/jn.2001.85.2.679
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发表时间：
2001-02-01
影响因子：
2.5
通讯作者：
Drew, T
中科院分区：
文献类型：
--
作者：
Prentice, SD;Drew, T
为了验证网状脊髓神经元（rsn）参与运动过程中伴随视觉触发的肢体轨迹自主改变的动态姿势调整的形成这一假设，我们在运动任务中记录了桥髓网状结构（PMRF）中400个细胞（183个rsn； 217个未识别的网状细胞）的活动。在该任务中，要求完整的猫跨过附着在移动跑步机带上的障碍物。当猫跨过障碍物时，大约一半的rsn（97/183, 53%）的细胞活性发生了显著变化；大多数细胞表现出单次（26/97,26.8%）或多次（63/97,65.0%）的活性增加。尽管不同细胞中的单个脉冲往往发生在步态周期的相似阶段，但放电模式的数量、时间和顺序都有所不同。大多数被修饰的细胞，不管放电增加的次数，也不管在无阻碍、控制、运动时细胞的放电活动，在前肢通过障碍物时放电。因此，当记录部位同侧前肢首先通过障碍物时，86.9%的修饰细胞的放电增加，而当对侧肢体首先通过障碍物时，这一比例为72.2%。在领先（27.1%）和落后（27.9%）两种情况下，大约四分之一的rsn在四肢通过障碍物时放电增加。一般来说，在任何一个细胞中，在导联和导联条件下，后续爆发的数量和相对顺序（相对于前肢）都保持不变。在未识别的细胞中观察到的活动模式与RSN活动非常相似，尽管这个未识别的细胞群可能代表不同的细胞群。我们认为，我们在这些网状神经元中观察到的放电增加反映了来自几个来源的传入活动的整合，包括运动皮层，并且这种放电增加的信号表明了伴随自主步态改变的姿势模式的时间和相对大小。然而，基于这些细胞中神经元活动模式的特征，我们进一步提出，虽然个体rsn可能有助于选择不同的姿势活动模式，但姿势反应的最终表达可能由脊髓内运动回路的兴奋性决定。
To test the hypothesis that reticulospinal neurons (RSNs) are involved in the formation of the dynamic postural adjustments that accompany visually triggered, voluntary modifications of limb trajectory during locomotion, we recorded the activity of 400 cells (183 RSNs; 217 unidentified reticular cells) in the pontomedullary reticular formation (PMRF) during a locomotor task in which intact cats were required to step over an obstacle attached to a moving treadmill belt. Approximately one half of the RSNs (97/183, 53%) showed significant changes in cell activity as the cat stepped over the obstacle; most of these cells exhibited either single (26/97, 26.8%) or multiple (63/97, 65.0%) increases of activity. There was a range of discharge patterns that varied in the number, timing, and sequencing of the bursts of modified activity, although individual bursts in different cells tended to occur at similar phases of the gait cycle. Most modified cells, regardless of the number of bursts of increased discharge, or of the discharge activity of the cell during unobstructed, control, locomotion, discharged during the passage of the lead forelimb over the obstacle. Thus, 86.9% of the modified cells increased their discharge when the forelimb ipsilateral to the recording site was the first to pass over the obstacle, and 72.2% when the contralateral limb was the first. Approximately one quarter of the RSNs increased their discharge during the passage of each of the four limbs over the obstacle in both the lead (27.1%) and trail (27.9%) conditions. In general, in any one cell, the number and relative sequencing of the subsequent bursts (with respect to the lead forelimb) was maintained during both lead and trail conditions. Patterns of activity observed in unidentified cells were very similar to the RSN activity despite the diverse population of cells this unidentified group may represent. We suggest that the increased discharge that we observed in these reticular neurons reflects the integration of afferent activity from several sources, including the motor cortex, and that this increased discharge signals the timing and the relative magnitude of the postural patterns that accompany the voluntary gait modification. However, based on the characteristics of the patterns of neuronal activity in these cells, we further suggest that while individual RSNs probably contribute to the selection of different patterns of postural activity, the ultimate expression of the postural response may be determined by the excitability of the locomotor circuits within the spinal cord.