The role of network structure in the central nervous control of caterpillar crawling and casting
Ewing, Elise M.
- Through numerical simulation, this study aims to understand a neuronal network that could be responsible for controlling several different behaviors of the caterpillar Manduca sexta, in hopes that the knowledge gained will be applicable to crawling in other caterpil- lars and soft-bodied units in general. Knowledge from previous studies has been compiled in order to determine target output patterns ... read morefor our networks. Qualitatively, the crawling pattern consists of a slow posterior to anterior propagating wave of bursts of activity within the ganglia of the abdominal body segments in Manduca. Another behavior that we con- sider is casting, which is a side-to-side motion believed to be a searching behavior. This behavior is characterized by laterally anti-synchronous bursting within a ganglion that is concurrent in successive posterior and anterior ganglia. One side of the caterpillar is active, and then the other. Working from simple feasible network designs, simulations were run in order to determine parameter regimes where our network could produce different desired outputs. We have found that a bilateral network of inhibitory neurons with adaptation cur- rents can produce either synchronous or anti-synchronous behavior when stimulated under different initial conditions. We have also found that the slow anterior propagating wave of the crawling pattern can be produced in a network of anterior linked excitatory neurons if those neurons release neurotransmitter that persists for a relatively long time in the synapse, and each neuron is self-inhibited by an adaptation current that acts on an even slower time scale.read less