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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 conceptual model used in this paper.On the left are the biological mechanisms that support the model: (1) SMA is illustrated by the muscle contraction (large arrows), (2) the spinal reflex circuits, which mediate afferent (green) and efferent (red) connections, and (3) the descending signals from supraspinal circuits (blue), which modulate the activity of reflex circuits. Unfilled and filled circles illustrate the presence of excitatory and inhibitory reflex circuits, respectively. On the right, is the general model with the abstracted biological mechanisms as well as the processes that link them together, i.e. self-organization and modulation.
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pcbi-1003653-g001: The conceptual model used in this paper.On the left are the biological mechanisms that support the model: (1) SMA is illustrated by the muscle contraction (large arrows), (2) the spinal reflex circuits, which mediate afferent (green) and efferent (red) connections, and (3) the descending signals from supraspinal circuits (blue), which modulate the activity of reflex circuits. Unfilled and filled circles illustrate the presence of excitatory and inhibitory reflex circuits, respectively. On the right, is the general model with the abstracted biological mechanisms as well as the processes that link them together, i.e. self-organization and modulation.

Mentions: From a theoretical perspective, we adopt the view that development is a key aspect to understand how the nervous system achieves coordinated behaviour [26]–[28]. Following this view, this paper proposes a computational model that links three behaviours which appear at different stages of development; in order of appearance these behaviours are: spontaneous motor activity (SMA), reflexes, and coordinated behaviour (see Figure 1). The model proposed identifies the mechanisms according to which (1) SMA propels the self-organization of adaptive reflex circuits, and (2) reflex circuits are manipulated to achieve coordinated behaviour. The main motivation to build our model is to validate in silico four hypotheses that are currently very difficult to verify in vivo. First, we hypothesise that SMA induces sensory and motor responses which are sufficient to self-organize reflex circuits. This has been shown in vivo in the case of the spinal withdrawal reflex [29], but has not yet been established for other reflexes. Second, we hypothesise that, once meaningful reflex circuitry is in place, it can be modulated to achieve coordinated behaviour. Third, we hypothesise that, since SMA is observed after birth, throughout the entire lifetime of an individual, it provides a mechanism to continuously adapt the reflex circuits to potential morphological changes (e.g. due to injury or growth). And fourth, we hypothesise that we can achieve behavioural transitions (i.e. switch between different behaviours) by changing the modulation of the reflex gains over time.


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

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

The conceptual model used in this paper.On the left are the biological mechanisms that support the model: (1) SMA is illustrated by the muscle contraction (large arrows), (2) the spinal reflex circuits, which mediate afferent (green) and efferent (red) connections, and (3) the descending signals from supraspinal circuits (blue), which modulate the activity of reflex circuits. Unfilled and filled circles illustrate the presence of excitatory and inhibitory reflex circuits, respectively. On the right, is the general model with the abstracted biological mechanisms as well as the processes that link them together, i.e. self-organization and modulation.
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1003653-g001: The conceptual model used in this paper.On the left are the biological mechanisms that support the model: (1) SMA is illustrated by the muscle contraction (large arrows), (2) the spinal reflex circuits, which mediate afferent (green) and efferent (red) connections, and (3) the descending signals from supraspinal circuits (blue), which modulate the activity of reflex circuits. Unfilled and filled circles illustrate the presence of excitatory and inhibitory reflex circuits, respectively. On the right, is the general model with the abstracted biological mechanisms as well as the processes that link them together, i.e. self-organization and modulation.
Mentions: From a theoretical perspective, we adopt the view that development is a key aspect to understand how the nervous system achieves coordinated behaviour [26]–[28]. Following this view, this paper proposes a computational model that links three behaviours which appear at different stages of development; in order of appearance these behaviours are: spontaneous motor activity (SMA), reflexes, and coordinated behaviour (see Figure 1). The model proposed identifies the mechanisms according to which (1) SMA propels the self-organization of adaptive reflex circuits, and (2) reflex circuits are manipulated to achieve coordinated behaviour. The main motivation to build our model is to validate in silico four hypotheses that are currently very difficult to verify in vivo. First, we hypothesise that SMA induces sensory and motor responses which are sufficient to self-organize reflex circuits. This has been shown in vivo in the case of the spinal withdrawal reflex [29], but has not yet been established for other reflexes. Second, we hypothesise that, once meaningful reflex circuitry is in place, it can be modulated to achieve coordinated behaviour. Third, we hypothesise that, since SMA is observed after birth, throughout the entire lifetime of an individual, it provides a mechanism to continuously adapt the reflex circuits to potential morphological changes (e.g. due to injury or growth). And fourth, we hypothesise that we can achieve behavioural transitions (i.e. switch between different behaviours) by changing the modulation of the reflex gains over time.

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
Related in: MedlinePlus