Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern Generator
The timing patterns of animal gaits are produced by a network of spinal neurons called a Central Pattern Generator (CPG). Pinto and Golubitsky studied a four-node CPG for biped dynamics in which each leg is associated with one flexor node and one extensor node, with Ζ2 x Ζ2 symmetry. They used symme...
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| Format: | Article |
| Language: | English |
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MDPI AG
2014-01-01
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| Series: | Symmetry |
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| Online Access: | http://www.mdpi.com/2073-8994/6/1/23 |
| _version_ | 1811187114010738688 |
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| author | Ian Stewart |
| author_facet | Ian Stewart |
| author_sort | Ian Stewart |
| collection | DOAJ |
| description | The timing patterns of animal gaits are produced by a network of spinal neurons called a Central Pattern Generator (CPG). Pinto and Golubitsky studied a four-node CPG for biped dynamics in which each leg is associated with one flexor node and one extensor node, with Ζ2 x Ζ2 symmetry. They used symmetric bifurcation theory to predict the existence of four primary gaits and seven secondary gaits. We use methods from symmetric bifurcation theory to investigate local bifurcation, both steady-state and Hopf, for their network architecture in a rate model. Rate models incorporate parameters corresponding to the strengths of connections in the CPG: positive for excitatory connections and negative for inhibitory ones. The three-dimensional space of connection strengths is partitioned into regions that correspond to the first local bifurcation from a fully symmetric equilibrium. The partition is polyhedral, and its symmetry group is that of a tetrahedron. It comprises two concentric tetrahedra, subdivided by various symmetry planes. The tetrahedral symmetry arises from the structure of the eigenvalues of the connection matrix, which is involved in, but not equal to, the Jacobian of the rate model at bifurcation points. Some of the results apply to rate equations on more general networks. |
| first_indexed | 2024-04-11T13:56:44Z |
| format | Article |
| id | doaj.art-1161287178ca49a19a68315452e14dd1 |
| institution | Directory Open Access Journal |
| issn | 2073-8994 |
| language | English |
| last_indexed | 2024-04-11T13:56:44Z |
| publishDate | 2014-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Symmetry |
| spelling | doaj.art-1161287178ca49a19a68315452e14dd12022-12-22T04:20:13ZengMDPI AGSymmetry2073-89942014-01-0161236610.3390/sym6010023sym6010023Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern GeneratorIan Stewart0Mathematics Institute, University of Warwick, Coventry CV4 7AL, UKThe timing patterns of animal gaits are produced by a network of spinal neurons called a Central Pattern Generator (CPG). Pinto and Golubitsky studied a four-node CPG for biped dynamics in which each leg is associated with one flexor node and one extensor node, with Ζ2 x Ζ2 symmetry. They used symmetric bifurcation theory to predict the existence of four primary gaits and seven secondary gaits. We use methods from symmetric bifurcation theory to investigate local bifurcation, both steady-state and Hopf, for their network architecture in a rate model. Rate models incorporate parameters corresponding to the strengths of connections in the CPG: positive for excitatory connections and negative for inhibitory ones. The three-dimensional space of connection strengths is partitioned into regions that correspond to the first local bifurcation from a fully symmetric equilibrium. The partition is polyhedral, and its symmetry group is that of a tetrahedron. It comprises two concentric tetrahedra, subdivided by various symmetry planes. The tetrahedral symmetry arises from the structure of the eigenvalues of the connection matrix, which is involved in, but not equal to, the Jacobian of the rate model at bifurcation points. Some of the results apply to rate equations on more general networks.http://www.mdpi.com/2073-8994/6/1/23biped gaitsymmetry-breakingrate modelnetworkHopf bifurcationtetrahedral group |
| spellingShingle | Ian Stewart Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern Generator Symmetry biped gait symmetry-breaking rate model network Hopf bifurcation tetrahedral group |
| title | Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern Generator |
| title_full | Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern Generator |
| title_fullStr | Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern Generator |
| title_full_unstemmed | Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern Generator |
| title_short | Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern Generator |
| title_sort | symmetry breaking in a rate model for a biped locomotion central pattern generator |
| topic | biped gait symmetry-breaking rate model network Hopf bifurcation tetrahedral group |
| url | http://www.mdpi.com/2073-8994/6/1/23 |
| work_keys_str_mv | AT ianstewart symmetrybreakinginaratemodelforabipedlocomotioncentralpatterngenerator |