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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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Leg trajectories during point-to-point tasks.The black lines display the initial leg position set for the point-to-point tasks, and the gray lines indicate the leg position achieved at the end of three different trajectories T1, T2, and T3.
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pcbi-1003653-g014: Leg trajectories during point-to-point tasks.The black lines display the initial leg position set for the point-to-point tasks, and the gray lines indicate the leg position achieved at the end of three different trajectories T1, T2, and T3.

Mentions: The experiment uses the reflexes learnt for the default leg model (see Figure 4). Prior to the experiment, we manually position the leg in three different postures. For each posture, we record the muscle lengths of all the muscles, such that we obtain three sets of muscle lengths and Subsequently, we assign sequentially each of the recorded sets of muscle lengths to the set of desired lengths of all the muscles. This assignment produces a change in the active resting length of the muscle, and induces sensory activity in the secondary afferent fibers. This activity, when propagated through the reflex matrix (see eq. 6), leads to a change in the resting position of the leg. The three sets of muscle lengths are applied with the leg in the same initial posture, which is the same as that used in the hopping experiments (see black lines in Figure 14). The and are set manually to minimize the oscillations of the end effector during a given trajectory.


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

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

Leg trajectories during point-to-point tasks.The black lines display the initial leg position set for the point-to-point tasks, and the gray lines indicate the leg position achieved at the end of three different trajectories T1, T2, and T3.
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1003653-g014: Leg trajectories during point-to-point tasks.The black lines display the initial leg position set for the point-to-point tasks, and the gray lines indicate the leg position achieved at the end of three different trajectories T1, T2, and T3.
Mentions: The experiment uses the reflexes learnt for the default leg model (see Figure 4). Prior to the experiment, we manually position the leg in three different postures. For each posture, we record the muscle lengths of all the muscles, such that we obtain three sets of muscle lengths and Subsequently, we assign sequentially each of the recorded sets of muscle lengths to the set of desired lengths of all the muscles. This assignment produces a change in the active resting length of the muscle, and induces sensory activity in the secondary afferent fibers. This activity, when propagated through the reflex matrix (see eq. 6), leads to a change in the resting position of the leg. The three sets of muscle lengths are applied with the leg in the same initial posture, which is the same as that used in the hopping experiments (see black lines in Figure 14). The and are set manually to minimize the oscillations of the end effector during a given trajectory.

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