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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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Hopping transitions.a) The hopping height achieved after the behavioural transition and b) detail of a showing the behavioural transition.
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pcbi-1003653-g013: Hopping transitions.a) The hopping height achieved after the behavioural transition and b) detail of a showing the behavioural transition.

Mentions: Another important aspect of the dynamic tuning of gains can be found in the transitions between different behavioural patterns. To test the hypothesis that behavioural transitions can be obtained by changing the modulation gains over time we carried out one additional experiment. In this experiment we show the switching from a standing behaviour, which keeps the leg standing on the ground, to the dynamic hopping behaviour described in the previous sections. We start the experiment by identifying three pairs of gains: one pair that allowed the leg to stand on the ground holding its own weight, another pair that caused the leg to fall down (basically, ), and a final pair of gains that produced the hopping behaviour (here, we use the same gains identified in the context of hopping with the default leg model in Figure 6a,c). We then set these gains sequentially; first we set the standing gains, then we set the falling gains for causing the leg to start falling, and finally we set the hopping gains. Our results are shown in Figure 13 (see also Movie S1.VII). As can be seen, the change in the gain parameters is sufficient for the system to achieve stable hopping starting from a standing position.


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

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

Hopping transitions.a) The hopping height achieved after the behavioural transition and b) detail of a showing the behavioural transition.
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1003653-g013: Hopping transitions.a) The hopping height achieved after the behavioural transition and b) detail of a showing the behavioural transition.
Mentions: Another important aspect of the dynamic tuning of gains can be found in the transitions between different behavioural patterns. To test the hypothesis that behavioural transitions can be obtained by changing the modulation gains over time we carried out one additional experiment. In this experiment we show the switching from a standing behaviour, which keeps the leg standing on the ground, to the dynamic hopping behaviour described in the previous sections. We start the experiment by identifying three pairs of gains: one pair that allowed the leg to stand on the ground holding its own weight, another pair that caused the leg to fall down (basically, ), and a final pair of gains that produced the hopping behaviour (here, we use the same gains identified in the context of hopping with the default leg model in Figure 6a,c). We then set these gains sequentially; first we set the standing gains, then we set the falling gains for causing the leg to start falling, and finally we set the hopping gains. Our results are shown in Figure 13 (see also Movie S1.VII). As can be seen, the change in the gain parameters is sufficient for the system to achieve stable hopping starting from a standing position.

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