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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 hip trajectory and the mean and standard deviation of the kinematic and dynamic variables obtained for the modified leg models.Kinematic and dynamic variables obtained for the system with a) four muscles, b) modified  and c) misplaced  S refers to the stance phase (when the end effector is in touch with the ground) and F refers to the flight phase (when the end effector is in the air). The hip trajectory recorded for the system with d) four muscles, e) modified  and f) misplaced
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pcbi-1003653-g009: The hip trajectory and the mean and standard deviation of the kinematic and dynamic variables obtained for the modified leg models.Kinematic and dynamic variables obtained for the system with a) four muscles, b) modified and c) misplaced S refers to the stance phase (when the end effector is in touch with the ground) and F refers to the flight phase (when the end effector is in the air). The hip trajectory recorded for the system with d) four muscles, e) modified and f) misplaced

Mentions: With respect to the removal of bi-articular muscles, the reflex weights obtained are similar to those in Figure 4, taking into account that any connections involving sensor or motor elements of the or are absent (given that these muscles do not exist in this modified leg model). The hopping behaviour achieved with this system is shown in Figure 9a,d. In spite of the larger oscillations in the muscle forces and in the joint angles observed during the flight phase of the movement, the system manages to achieve a stable hopping pattern () and to conserve the hopping height () (Figure 9d). The larger oscillations in the muscle forces and the joint angles achieved by this system, when compared to those in the default system, are consistent with mechanical observations described in [53], [54], where the stabilizing role of bi-articular muscles has been put forward.


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

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

The hip trajectory and the mean and standard deviation of the kinematic and dynamic variables obtained for the modified leg models.Kinematic and dynamic variables obtained for the system with a) four muscles, b) modified  and c) misplaced  S refers to the stance phase (when the end effector is in touch with the ground) and F refers to the flight phase (when the end effector is in the air). The hip trajectory recorded for the system with d) four muscles, e) modified  and f) misplaced
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1003653-g009: The hip trajectory and the mean and standard deviation of the kinematic and dynamic variables obtained for the modified leg models.Kinematic and dynamic variables obtained for the system with a) four muscles, b) modified and c) misplaced S refers to the stance phase (when the end effector is in touch with the ground) and F refers to the flight phase (when the end effector is in the air). The hip trajectory recorded for the system with d) four muscles, e) modified and f) misplaced
Mentions: With respect to the removal of bi-articular muscles, the reflex weights obtained are similar to those in Figure 4, taking into account that any connections involving sensor or motor elements of the or are absent (given that these muscles do not exist in this modified leg model). The hopping behaviour achieved with this system is shown in Figure 9a,d. In spite of the larger oscillations in the muscle forces and in the joint angles observed during the flight phase of the movement, the system manages to achieve a stable hopping pattern () and to conserve the hopping height () (Figure 9d). The larger oscillations in the muscle forces and the joint angles achieved by this system, when compared to those in the default system, are consistent with mechanical observations described in [53], [54], where the stabilizing role of bi-articular muscles has been put forward.

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