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From spontaneous motor activity to coordinated behaviour: a developmental model.

Marques HG, Bharadwaj A, Iida F - PLoS Comput. Biol. (2014)

Bottom Line: Our model is tested in a simulated musculoskeletal leg actuated by six muscles arranged in a number of different ways.Hopping is used as a case study of coordinated behaviour.In addition, our results show that our model can naturally adapt to different morphological changes and perform behavioural transitions.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Mechanical and Process Engineering, ETH, Zurich, Switzerland.

ABSTRACT
In mammals, the developmental path that links the primary behaviours observed during foetal stages to the full fledged behaviours observed in adults is still beyond our understanding. Often theories of motor control try to deal with the process of incremental learning in an abstract and modular way without establishing any correspondence with the mammalian developmental stages. In this paper, we propose a computational model that links three distinct behaviours which appear at three different stages of development. In order of appearance, these behaviours are: spontaneous motor activity (SMA), reflexes, and coordinated behaviours, such as locomotion. The goal of our model is to address in silico four hypotheses that are currently hard to verify in vivo: First, the hypothesis that spinal reflex circuits can be self-organized from the sensor and motor activity induced by SMA. Second, the hypothesis that supraspinal systems can modulate reflex circuits to achieve coordinated behaviour. Third, the hypothesis that, since SMA is observed in an organism throughout its entire lifetime, it provides a mechanism suitable to maintain the reflex circuits aligned with the musculoskeletal system, and thus adapt to changes in body morphology. And fourth, the hypothesis that by changing the modulation of the reflex circuits over time, one can switch between different coordinated behaviours. Our model is tested in a simulated musculoskeletal leg actuated by six muscles arranged in a number of different ways. Hopping is used as a case study of coordinated behaviour. Our results show that reflex circuits can be self-organized from SMA, and that, once these circuits are in place, they can be modulated to achieve coordinated behaviour. In addition, our results show that our model can naturally adapt to different morphological changes and perform behavioural transitions.

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The hopping height progression achieved for different a)  and b) .The large magnitude of the gains is justified by the fact that we use SI units in the afferents –  for type-Ia afferents and  for type-II afferents.
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pcbi-1003653-g007: The hopping height progression achieved for different a) and b) .The large magnitude of the gains is justified by the fact that we use SI units in the afferents – for type-Ia afferents and for type-II afferents.

Mentions: To illustrate the importance of the gain parameter tuning process we show in Figure 6b the results obtained with parameters and smaller than those used in Figure 6a (see also Movie S1.II-III). With the new gains, the system is clearly unstable () and it does not fulfil the conservation of the hopping height criterion () as we observe a regular decrease in the hopping height (Figure 6d). Moreover this is accompanied by a clear increase in the standard deviation in all the muscle (and ground) forces as well as in the hip and knee angles (Figure 6b). A more in-depth analysis of the effect of each gain on the hopping stability is shown in Figure 7. In this experiment we varied each of the gain parameters and observed the progression of the hopping height. For each plot we modified one of the gains while keeping the other fixed at the value that produced the stable hopping pattern shown in Figure 6b. In Figure 7a we varied and in Figure 7b we varied in each plot represents the value of the respective gain that achieved the stable hopping pattern.


From spontaneous motor activity to coordinated behaviour: a developmental model.

Marques HG, Bharadwaj A, Iida F - PLoS Comput. Biol. (2014)

The hopping height progression achieved for different a)  and b) .The large magnitude of the gains is justified by the fact that we use SI units in the afferents –  for type-Ia afferents and  for type-II afferents.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109855&req=5

pcbi-1003653-g007: The hopping height progression achieved for different a) and b) .The large magnitude of the gains is justified by the fact that we use SI units in the afferents – for type-Ia afferents and for type-II afferents.
Mentions: To illustrate the importance of the gain parameter tuning process we show in Figure 6b the results obtained with parameters and smaller than those used in Figure 6a (see also Movie S1.II-III). With the new gains, the system is clearly unstable () and it does not fulfil the conservation of the hopping height criterion () as we observe a regular decrease in the hopping height (Figure 6d). Moreover this is accompanied by a clear increase in the standard deviation in all the muscle (and ground) forces as well as in the hip and knee angles (Figure 6b). A more in-depth analysis of the effect of each gain on the hopping stability is shown in Figure 7. In this experiment we varied each of the gain parameters and observed the progression of the hopping height. For each plot we modified one of the gains while keeping the other fixed at the value that produced the stable hopping pattern shown in Figure 6b. In Figure 7a we varied and in Figure 7b we varied in each plot represents the value of the respective gain that achieved the stable hopping pattern.

Bottom Line: Our model is tested in a simulated musculoskeletal leg actuated by six muscles arranged in a number of different ways.Hopping is used as a case study of coordinated behaviour.In addition, our results show that our model can naturally adapt to different morphological changes and perform behavioural transitions.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Mechanical and Process Engineering, ETH, Zurich, Switzerland.

ABSTRACT
In mammals, the developmental path that links the primary behaviours observed during foetal stages to the full fledged behaviours observed in adults is still beyond our understanding. Often theories of motor control try to deal with the process of incremental learning in an abstract and modular way without establishing any correspondence with the mammalian developmental stages. In this paper, we propose a computational model that links three distinct behaviours which appear at three different stages of development. In order of appearance, these behaviours are: spontaneous motor activity (SMA), reflexes, and coordinated behaviours, such as locomotion. The goal of our model is to address in silico four hypotheses that are currently hard to verify in vivo: First, the hypothesis that spinal reflex circuits can be self-organized from the sensor and motor activity induced by SMA. Second, the hypothesis that supraspinal systems can modulate reflex circuits to achieve coordinated behaviour. Third, the hypothesis that, since SMA is observed in an organism throughout its entire lifetime, it provides a mechanism suitable to maintain the reflex circuits aligned with the musculoskeletal system, and thus adapt to changes in body morphology. And fourth, the hypothesis that by changing the modulation of the reflex circuits over time, one can switch between different coordinated behaviours. Our model is tested in a simulated musculoskeletal leg actuated by six muscles arranged in a number of different ways. Hopping is used as a case study of coordinated behaviour. Our results show that reflex circuits can be self-organized from SMA, and that, once these circuits are in place, they can be modulated to achieve coordinated behaviour. In addition, our results show that our model can naturally adapt to different morphological changes and perform behavioural transitions.

Show MeSH
Related in: MedlinePlus