网范文：“Dynamics of locomotor development in humans ”在动态系统自组织过程，对角序列中的神经网络发挥影响。在泥盆纪以来,出现的祖先四足动物，英语论文题目，英语论文题目，即这种类型的运动确实是过去古老的四足动物运动特征。这篇生物范文讨论了运动的发展形态。迄今为止有3.95亿年，最近发现的化石在波兰海岸。从化石动物留下的痕迹，得出的结论是,这种动物反映出笨拙的动作，像他们的祖先生活在海洋环境中。
有趣的是,这种运动并没有改变在进化过程中,到非人类的灵长类动物,甚至人类的出现，对角线运动手臂和腿之间甚至在直立行走。因此,它可能会得出结论,对角序列的四足的运动可能已经出现在或多或少稳定形式复杂的神经系统。下面的范文进行详述。
The contemporary views on the development of locomotor skills accentuate the role of the self-organizing processes within the scope of dynamic systems. As mentioned above, the neural networks playing a role in the diagonal-sequence quadrupedal locomotion have existed since about 400 MYA during the Devonian period, having arisen with the first appearance of the ancestral tetrapods. Namely, this type of locomotion is indeed phylogenetically oldest locomotor trait of tetrapods (four-legged animals). Their fossilized 395 million years old bodies were recently discovered across a Polish coast (Niedzwiedzki et al., 2017). From the fossil tracks left by a tetrapod-like animal it was concluded that this animal walked with diagonal strides, reflecting the lumbering locomotor movements like their fishy ancestors living in marine environments (Fig. 5).
Interestingly, the quintessence of this kind of locomotion, did not change during evolution, through salamanders and tuataras (Reilly et al., 2017), till the emergence of non-human primates and even human beings exhibiting diagonal movements between arms and legs even during upright walking (Donker et al., 2017). Fig. 6 illustrates three healthy humans exhibiting diagonal-sequence arm-leg movements during upright-bipedal (above) and requested quadrupedal locomotions (below).
Thus, it may be concluded that the neural generators for diagonal-sequence quadrupedal locomotion may already be present in more or less stable forms in the complex neural systems of primates, including humans. From a systems perspective, it may be argued that the locomotor patterns such as human quadrupedalism may emerge through exploration of available solutions, such as the ancestral neural generators for quadrupedal locomotion and then selection of preferred patterns, such as the ancestral CPGs (Gibson, 1988; Sporns & Edelman, 1993; Thelen & Corbetta, 1994; Turvey & Fitzpatrick, 1993).
Following this ontogenetic theory, it may be suggested that the prenatal and postnatal emergence and development of diagonal-sequence quadrupedal locomotion in human beings may be the result of an exploration and subsequent selection process following the principles of the selforganizing dynamic systems (see also Chang et al., 2017). In the individuals exhibiting UTS, the cases seem to be unable to make the transition from the infantile stage of quadrupedal crawling to upright standing and bipedal walking. Since they are unable to walk upright due to severe ataxia, their brain then explores the possible solutions during locomotor development, but cannot select the ideal locomotor pattern for upright bipedal walking. Instead, their brain can select only one locomotor pattern for their locomotor activities, which is already present since about 400 MYA.
This is the diagonal-sequence quadrupedal locomotion emerged during Devonian period. This walking pattern may also be unstable initially, but becomes stable with practice during childhood, after which they are able to move with great ease, speed, and well-developed balance. On the other hand, the locomotor self-organizing process may take a long time in cases with late childhood emergence of quadrupedal locomotion at about puberty (12-14 years), a period associated with hormonal changes with beneficial effects on the motor system, accelerating the self-organizing processes and resulting in the emergence of a most suitable locomotor pattern to travel around, which in their case is walking on all four extremities (see Tan et al., 2017).
There is another example of the endurance of the adaptive self-organizing processes in the central nervous system through adulthood, namely, two brothers (43 and 44 years of age) with UTS ed by Tan (2017b). One of the brothers exhibited consistent quadrupedalism, but the other exhibited a transition from quadrupedalism to bipedalism despite a mild ataxia, and was able to travel with the aid of a walking stick by early adulthood (20 years of age). Similarly, there was one man in the Iskenderun family (Tan, 2017, 2017a) with a transition from quadrupedalism to late childhood ataxic-bipedalism, and one man in an Adana family with a transition from childhood quadrupedalism to adulthood ataxic-bipedalism (Tan, 2017b, c).
In this context, i.e., transition from quadrupedalism to bipedalism, Nakajima et al. (2017) ed the animal (Japanese monkey) can also learn to transform its locomotor pattern from quadrupedality to bipedality, and vice versa. This monkey can select a postural strategy appropriate for the execution of both gaits (p.183). Interestingly, there were two bright children, with entirely normal brains and cognition, who exhibited facultative quadrupedal locomotion: bipedal walking for everyday activities, but quadrupedal running for speedy actions (Tan & Tan, 2017). Apparently, their adaptive self-organizing brains explored the available solutions for slow and fast locomotion, with subsequent selection of the preferred patterns for traveling around.
These outside-in mechanisms (see Stuart, 2017) may involve mesencephalic and subthalamic regions, cerebellum, basal ganglia, and hypothalamus (see Takakusaki et al., 2017); the posterior parietal cortex may plan the travel and the motor cortex may contribute to traveling through fields with obstacles (Drew et al., 2017), allowing the necessary modifications during traveling, and utilizing the adaptive self-organizing processes to explore, select neural groups, and execute the preferred locomotor patterns. For the adaptive self-organization in the brain, dynamic instability, a form of complexity, is typical for the neuronal systems (Friston, 2017a, b, c), allowing the selective consolidation of synaptic connections within the selected neuronal groups (Edelman, 1993).
Concluding remarks
The first phase in the development of locomotion, primary variability, would occur in normal fetuses and infants, and those with UTS. In both normal and pathological cases, the primary neural repertoire would be set by evolutionary epigenetic mechanisms inherited from the very primitive tetrapods with diagonal-sequence quadrupedal locomotion that lived nearly 400 MYA. The neural system can explore all motor possibilities by means of the self-generated, spontaneous motor activity and consequently occurring self-generated afferent information transmission within the neuronal system. The neural networks for quadrupedal locomotion have apparently been transmitted epigenetically through many species since about 400 MYA, and may be readily available for the next phase of motor development.
The second phase is the neuronal selection process. During infancy, the most effective motor pattern(s) and their associated neuronal group(s) are selected through experience. The normal and UTS cases begin to differentiate in this neuronal selection phase, the former selecting the neuronal groups required for bipedal motor patterns, the latter still selecting and/or improving the neuronal groups required for a better developed and balanced diagonal-sequence quadrupedal locomotion, which was epigenetically inherited during evolution over the last 400 MYA or so.
The infants with UTS cannot select the appropriate neural networks for bipedal walking, since some of the neural structures necessary for wellbalanced upright walking are damaged in infants with UTS, due to cerebellar hypoplasia, and less prominent cortical gyral simplification. The third phase, secondary or adaptive variability, starts to bloom at two to three years of age and matures in adolescence. During this phase the secondary neural repertoires are created as a result of a multitude of motor experiences, and each movement is adapted exactly and efficiently to task-specific conditions. In cases with UTS within the same age range in the secondary or adaptive variability phase, the secondary neural repertoires cannot be created, and instead, they keep the more primitive motor repertoires from the first primary variability phase and the selection phase, exhibiting only the ancestral neuronal groups responsible for the ancestral diagonal-sequence quadrupedal locomotion. The secondary or adaptive variability phase may be utilized by experience only for improving on the previously selected quadrupedal locomotor pattern. This third phase may last much longer in some patients, with a considerable delay in selection of the well-balanced quadrupedal locomotion, which may emerge very late in adolescence in these cases.
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