Preprint: a neuromechanical simulation of gait transition in salamander

[ijspeert]

Dear Connectionists,

Preprints of a paper to appear in Biological Cybernetics addressing the
neural control of locomotion and gait transition in salamander are
available for download from the following sites:

http://rana.usc.edu:8376/~ijspeert/publications.html

http://rana.usc.edu:8376/~ijspeert/PAPERS/BC.ps.gz
http://rana.usc.edu:8376/~ijspeert/PAPERS/BC.pdf

The paper (see abstract below) presents a neuromechanical model capable of
exhibiting the typical swimming and walking gaits of the salamander.
Animations of the salamander simulation can be viewed at
http://rana.usc.edu:8376/~ijspeert/salamander.html

Comments are most welcome.

Best regards,

Auke Ijspeert


---------------------------------------------------------------------------
    Dr Auke Jan Ijspeert                                              
    Brain Simulation Lab & Computational Learning and Motor Control Lab 
    Dept. of Computer Science, Hedco Neurosciences bldg, 3641 Watt way      
    U. of Southern California, Los Angeles, CA 90089-2520, USA             
    Web:   http://rana.usc.edu:8376/~ijspeert/                        
    Tel:   +1 213 7401922 or 7406995 (work) +1 310 8238087 (home)     
    Fax:   +1 213 7405687                                                  
    Email: ijspeert at usc.edu                                      
---------------------------------------------------------------------------


A connectionist central pattern generator for the aquatic and terrestrial
gaits of a simulated salamander

Auke Jan Ijspeert

Abstract:

This article investigates the neural mechanisms underlying salamander
locomotion, and develops a biologically plausible connectionist model of a
central pattern generator capable of producing the typical aquatic and
terrestrial gaits of the salamander. It investigates, in particular, what
type of neural circuitry can produce and modulate the two locomotor
programs identified within the salamander's spinal cord, namely, a
traveling wave of neural activity for swimming and a standing wave for
trotting.
 
A two-dimensional biomechanical simulation of the salamander's body is
developed whose muscle contraction is determined by the locomotion
controller simulated as a leaky-integrator neural network. While the
connectivity of the neural circuitry underlying locomotion in the
salamander has not been decoded for the moment, this article presents the
design of a neural circuit which has a general organization corresponding
to that hypothesized by neurobiologists.  In particular, the locomotion
controller is based on a body {\it central pattern generator} (CPG)
corresponding to a lamprey-like swimming controller, and is extended with
a limb CPG for controlling the salamander's limbs. The complete controller
is developed in three stages, with first the development of segmental
oscillators, second the development of intersegmental coupling for the
making of a lamprey-like swimming CPG, and finally the development of the
limb CPG and its coupling with the body CPG. A genetic algorithm is used
to instantiate the parameters of the neural circuit for the different
stages given a high level description of the desired state space
trajectories of the different subnetworks. A controller is thus developed
which can produce neural activities and locomotion gaits very similar to
those observed in the real salamander. By varying the tonic (i.e.
non-oscillating) excitation applied to the network, the speed, direction
and type of gait can be varied.