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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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Hinton diagrams of the reflex circuits obtained with the default leg model.a) Circuits obtained for the Ia-type afferents, and b) those obtained for the II-type afferents. Unfilled circles represent excitatory connections, and filled circles represent inhibitory connections.
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pcbi-1003653-g004: Hinton diagrams of the reflex circuits obtained with the default leg model.a) Circuits obtained for the Ia-type afferents, and b) those obtained for the II-type afferents. Unfilled circles represent excitatory connections, and filled circles represent inhibitory connections.

Mentions: We first address the hypothesis that meaningful reflex circuits can be self-organized from SMA. The experiment is carried out by triggering ten twitches in each muscle of the default leg model and by correlating the resulting sensor and motor activity during the passive stage. The reflex circuits obtained are shown in Figure 4. These circuits were obtained using a twitch amplitude of which produces almost unoticeable muscle contractions. In Figure S1 we show the reflex circuits obtained with an activation of (see Movie S1). The figures show connectivity matrices in which each element represents a connection between a sensor and a motor elements. Unfilled circles represent excitatory connections, filled circles represent inhibitory connections; the size of the circle represents the magnitude of the connection.


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

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

Hinton diagrams of the reflex circuits obtained with the default leg model.a) Circuits obtained for the Ia-type afferents, and b) those obtained for the II-type afferents. Unfilled circles represent excitatory connections, and filled circles represent inhibitory connections.
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1003653-g004: Hinton diagrams of the reflex circuits obtained with the default leg model.a) Circuits obtained for the Ia-type afferents, and b) those obtained for the II-type afferents. Unfilled circles represent excitatory connections, and filled circles represent inhibitory connections.
Mentions: We first address the hypothesis that meaningful reflex circuits can be self-organized from SMA. The experiment is carried out by triggering ten twitches in each muscle of the default leg model and by correlating the resulting sensor and motor activity during the passive stage. The reflex circuits obtained are shown in Figure 4. These circuits were obtained using a twitch amplitude of which produces almost unoticeable muscle contractions. In Figure S1 we show the reflex circuits obtained with an activation of (see Movie S1). The figures show connectivity matrices in which each element represents a connection between a sensor and a motor elements. Unfilled circles represent excitatory connections, filled circles represent inhibitory connections; the size of the circle represents the magnitude of the connection.

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