Parameter space analysis suggests multi-site plasticity contributes to motor pattern initiation in Tritonia

Area of Science:

• Neuroscience
• Computational Biology
• Animal Behavior

Background:

• The central pattern generator (CPG) network controls rhythmic behaviors like escape swimming in Tritonia diomedea.
• Network activation involves external stimuli, intrinsic neuromodulation, and increased excitation.

Purpose of the Study:

• To investigate the mechanisms initiating rhythmic activity in the Tritonia escape swim CPG.
• To determine the necessary conditions for activating the CPG beyond extrinsic input.

Main Methods:

• Constructed a detailed computational model of the unmodulated CPG network based on physiological data.
• Performed a large-scale parameter-space analysis of approximately 2 million configurations.
• Investigated the roles of neuromodulation, polysynaptic effects, and network reconfiguration.

Main Results:

• Extrinsic input alone was insufficient to trigger rhythmic activity in the model.
• Incorporating known modulatory and polysynaptic effects did not fully enable rhythmic activity.
• Significant network reconfiguration, including ventral swim interneuron-B (VSI) recruitment and enhanced dorsal swim interneuron-C2 coupling, was required.

Conclusions:

• CPG activation necessitates substantial network restructuring, not just external triggers.
• The initiation of episodic rhythmic activity may involve a temporary shift from a nonrhythmic to an oscillatory state.
• Neuromodulatory timing likely regulates the activation and cessation of rhythmic bursting patterns.