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Tham khảo tài liệu 'adaptive motion of animals and machines - hiroshi kimura et al (eds) part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 200 Gentaro Taga freezing and freeing degrees of freedom is one of the key mechanisms for the acquisition of bipedal locomotion during development. A prominent feature of locomotor development is that newborn infants who are held erect under their arms perform locomotor-like activity 35 . The existence of newborn stepping behavior implies that the neural system already contains a CPG for rhythmic movements of the lower limbs. Interestingly this behavior disappears after the first few months. Then around one year of age infants start walking independently. Why are the successive appearance disappearance and reappearance of stepping observed in the development of locomotion According to traditional neurology the disappearance of motor patterns is due to the maturation of the cerebral cortex which inhibits the generation of movements on the spinal level. However it was reported that the stepping of infants of a few months of age can be easily induced on a treadmill 35 . It is likely that the spinal CPG is used for the generation of independent walking. I hypothesized that this change reflects the freezing and freeing degrees of freedom of the neuro-musculo-skeletal system which may be produced by the interaction between a neural rhythm generator RG composed of neural oscillators and a posture controller PC . A computational model was constructed to reproduce qualitative changes in motor patterns during development of locomotion by the following sequence of changes in the structure and parameters of the model as shown in Fig. 9 18 . 1 It was assumed that the RG of newborn infants consists of six neural oscillators which interact through simple excitatory connections and that the PC is not yet functioning. When the body was mechanically supported and the RG was activated the model produced a stepping movement which was similar to newborn stepping. Tightly synchronized movements of the joints were generated by highly synchronized activities of the neural oscillators on .
