Inhaltsverzeichnis - Mathematisches Institut der Universität zu Köln

DMV Tagung 2011 - Köln, 19. - 22. September
Silvia Daun–Gruhn, Tibor I. Tóth
Emmy-Noether Research Group, Zoological Institute, University of Cologne
A model of the levator-depressor neuro-mechanical system of the stick insect leg
It has been established experimentally that each joint in the stick insect leg is associated with its own
rhythm generating neural network (CPG), which is responsible for driving the motoneurons (MNs) that
innervate antagonistic muscle pairs [1]. This arrangement ensures large flexibility of the leg movements
in these animals. But how exactly do these CPG-MN-muscles systems function? And how is sensory
information integrated to produce functional stepping?
To tackle these questions, we developed a mathematical model of the levator-depressor neuro-mechanical
system, which consists of a half-center oscillator [2] that controls the MN activity via inhibitory interneurons
[3]. A sensory pathway to the CPG, conveying information on the loading of the leg, is included
as well. The core of the mechanical model is the equation of motion of the femur. The muscles are
modeled as nonlinear springs with variable elasticity modules and with viscous damping parallel to the
springs. Finally, the neural and the muscle systems are coupled by a linear, 1st order synapse model [4].
Our model successfully reproduces the MN activities, as well as the angular movement of the femur as
recorded during straightforward locomotion. Furthermore, our simulations provide strong evidence for a
high behavioral flexibility of the model under various peripheral or central influences.
Literatur
Büschges, A., Schmitz, J., Bässler, U. (1995). Rhythmic patterns in the thoracic nerve cord of the stick
insect induced by pilocarpine. J Exp Biol, 198, 435 - 456.
Daun, S., Rybak, I.A., Rubin, J. (2009). The response of a half-center oscillator to external drive depends
on the intrinsic dynamics of its components: a mechanistic analysis. J comput Neurosci, 27, 3 - 36.
Daun-Gruhn, S., Toth, T.I. (2010). An inter-segmental network model and its use in elucidating gaitswitches
in the stick insect. J comput Neurosci, doi:10.1007/s10827-010-0300-1.
Toth, T.I., Bessaih, T., Leresche, N., Crunelli, V. (2007). The properties of reticular thalamic neuron
GABA_A IPSCs of absence epilepsy rats lead to enhanced network excitability. Eur J Neurosci, 26, 1832
- 1844.
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