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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 learning framework.1) Spontaneous motor activity stimulates the motor system and 2) causes the muscles to contract. 3) The generated forces are propagated through the musculoskeletal system (and the environment) and induce sensor stimulation in the primary () and secondary () spindle afferent fibers. 4) The correlation between the sensor and motor signals is used to self-organize the reflex networks,  and  which mediate the connectivity of afferents  and  respectively. 5) The reflex circuits are modulated from supraspinal systems using gains  and  which independently scale the reflex networks  and  respectively.
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pcbi-1003653-g002: The learning framework.1) Spontaneous motor activity stimulates the motor system and 2) causes the muscles to contract. 3) The generated forces are propagated through the musculoskeletal system (and the environment) and induce sensor stimulation in the primary () and secondary () spindle afferent fibers. 4) The correlation between the sensor and motor signals is used to self-organize the reflex networks, and which mediate the connectivity of afferents and respectively. 5) The reflex circuits are modulated from supraspinal systems using gains and which independently scale the reflex networks and respectively.

Mentions: The information flow in our developmental model is shown in Figure 2; the passive stage involves steps 1–5 and the active stage involves step 6. The model can be summarised as follows. First, spontaneous motor activity generates muscle contractions in the form of muscle twitches. Second, these twitches produce muscle forces which are propagated through the musculoskeletal system (and the environment). Third, changes in the musculoskeletal state induce sensory information, which fourth activate various sensory receptors [26]. Fifth, the correlation between the sensor and motor signals determines the pattern of connectivity of the different reflex circuits [29], [30]. Sixth, once the reflex circuits are in place, their strength is modulated by supraspinal systems to achieve coordinated behaviour. In the following sections, we describe in detail each of the sub-models used as well as the experimental methods underlying our experiments; we will start with the musculoskeletal and the environment systems.


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

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

The learning framework.1) Spontaneous motor activity stimulates the motor system and 2) causes the muscles to contract. 3) The generated forces are propagated through the musculoskeletal system (and the environment) and induce sensor stimulation in the primary () and secondary () spindle afferent fibers. 4) The correlation between the sensor and motor signals is used to self-organize the reflex networks,  and  which mediate the connectivity of afferents  and  respectively. 5) The reflex circuits are modulated from supraspinal systems using gains  and  which independently scale the reflex networks  and  respectively.
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1003653-g002: The learning framework.1) Spontaneous motor activity stimulates the motor system and 2) causes the muscles to contract. 3) The generated forces are propagated through the musculoskeletal system (and the environment) and induce sensor stimulation in the primary () and secondary () spindle afferent fibers. 4) The correlation between the sensor and motor signals is used to self-organize the reflex networks, and which mediate the connectivity of afferents and respectively. 5) The reflex circuits are modulated from supraspinal systems using gains and which independently scale the reflex networks and respectively.
Mentions: The information flow in our developmental model is shown in Figure 2; the passive stage involves steps 1–5 and the active stage involves step 6. The model can be summarised as follows. First, spontaneous motor activity generates muscle contractions in the form of muscle twitches. Second, these twitches produce muscle forces which are propagated through the musculoskeletal system (and the environment). Third, changes in the musculoskeletal state induce sensory information, which fourth activate various sensory receptors [26]. Fifth, the correlation between the sensor and motor signals determines the pattern of connectivity of the different reflex circuits [29], [30]. Sixth, once the reflex circuits are in place, their strength is modulated by supraspinal systems to achieve coordinated behaviour. In the following sections, we describe in detail each of the sub-models used as well as the experimental methods underlying our experiments; we will start with the musculoskeletal and the environment systems.

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