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Left-Right Locomotor Coordination in Human Neonates
Journal of Neuroscience ( IF 5.3 ) Pub Date : 2022-08-24 , DOI: 10.1523/jneurosci.0612-22.2022
Arthur H Dewolf 1 , Valentina La Scaleia 2 , Adele Fabiano 3, 4 , Francesca Sylos-Labini 2 , Vito Mondi 3 , Simonetta Picone 3 , Ambrogio Di Paolo 4 , Piermichele Paolillo 3 , Yuri Ivanenko 2 , Francesco Lacquaniti 1, 2
Affiliation  

Terrestrial locomotion requires coordinated bilateral activation of limb muscles, with left–right alternation in walking or running, and synchronous activation in hopping or skipping. The neural mechanisms involved in interlimb coordination at birth are well known in different mammalian species, but less so in humans. Here, 46 neonates (of either sex) performed bilateral and unilateral stepping with one leg blocked in different positions. By recording EMG activities of lower-limb muscles, we observed episodes of left–right alternating or synchronous coordination. In most cases, the frequency of EMG oscillations during sequences of consecutive steps was approximately similar between the two sides, but in some cases it was considerably different, with episodes of 2:1 interlimb coordination and episodes of activity deletions on the blocked side. Hip position of the blocked limb significantly affected ipsilateral, but not contralateral, muscle activities. Thus, hip extension backward engaged hip flexor muscle, and hip flexion engaged hip extensors. Moreover, the sudden release of the blocked limb in the posterior position elicited the immediate initiation of the swing phase of the limb, with hip flexion and a burst of an ankle flexor muscle. Extensor muscles showed load responses at midstance. The variable interlimb coordination and its incomplete sensory modulation suggest that the neonatal locomotor networks do not operate in the same manner as in mature locomotion, also because of the limited cortical control at birth. These neonatal mechanisms share many properties with spinal mammalian preparations (i.e., independent pattern generators for each limb, and for flexor and extensor muscles, load, and hip position feedback).

SIGNIFICANCE STATEMENT Bilateral coupling and reciprocal activation of flexor and extensor burst generators represent the fundamental mechanisms used by mammalian limbed locomotion. Considerable progress has been made in deciphering the early development of the spinal networks and left–right coordination in different mammals, but less is known about human newborns. We compared bilateral and unilateral stepping in human neonates, where cortical control is still underdeveloped. We found neonatal mechanisms that share many properties with spinal mammalian preparations (i.e., independent pattern generators for each limb, the independent generators for flexor and extensor muscles, load, and hip-position feedback. The variable interlimb coordination and its incomplete sensory modulation suggest that the human neonatal locomotor networks do not operate in the same manner as in mature locomotion.



中文翻译:

人类新生儿的左右运动协调

地面运动需要协调双侧肢体肌肉激活,在行走或跑步时左右交替,在跳跃或跳跃时同步激活。出生时涉及肢间协调的神经机制在不同的哺乳动物物种中是众所周知的,但在人类中却鲜为人知。在这里,46 名新生儿(不限性别)进行了双侧和单侧踩踏,一条腿被固定在不同的位置。通过记录下肢肌肉的 EMG 活动,我们观察到左右交替或同步协调的发作。在大多数情况下,在连续步骤序列中,EMG 振荡的频率在两侧之间大致相似,但在某些情况下却有很大不同,在受阻侧有 2:1 肢间协调和活动缺失的发作。受阻肢体的髋部位置显着影响同侧而非对侧的肌肉活动。因此,髋关节向后伸展与髋屈肌相关,而髋关节屈曲与髋伸肌相关。此外,在后位突然释放受阻的肢体会立即引发肢体的摆动阶段,伴有髋关节屈曲和踝屈肌爆发。伸肌在站立中期表现出负荷反应。可变的肢间协调及其不完整的感觉调节表明新生儿运动网络的运作方式与成熟运动不同,这也是因为出生时皮质控制有限。这些新生儿机制与脊髓哺乳动物准备有许多共同特性(即,每个肢体的独立模式发生器,

重要性声明屈肌和伸肌爆发发生器的双边耦合和相互激活代表了哺乳动物四肢运动所使用的基本机制。在破译不同哺乳动物的脊柱网络和左右协调的早期发育方面取得了相当大的进展,但对人类新生儿知之甚少。我们比较了人类新生儿的双侧和单侧踩踏,其中皮质控制仍不发达。我们发现新生儿机制与脊柱哺乳动物准备有许多共同特性(即,每个肢体的独立模式发生器,屈肌和伸肌的独立发生器,负载和臀部位置反馈。

更新日期:2022-08-25
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