Motor pattern specification by dual descending pathways to a lobster rhythm-generating network

Area of Science:

• Neuroscience
• Crustacean biology
• Motor control

Background:

• The European lobster's gastric mill circuit controls rhythmic chewing.
• In vitro studies reveal a single motor program, differing from in vivo patterns.

Purpose of the Study:

• To identify neurons and synaptic connections in the lobster gastric mill network.
• To understand how external inputs modulate gastric mill activity.

Main Methods:

• Paired intrasomatic recordings to map neural circuitry.
• Stimulation of identified interneurons (CG and gastric inhibitor) to observe motor output.

Main Results:

• The gastric mill network comprises motoneurons with established synaptic relationships.
• Two projection interneurons (excitatory and inhibitory) influence the network.
• Stimulating the CG interneuron elicits a type I motor program; combined stimulation with the gastric inhibitor interneuron produces a type II pattern.

Conclusions:

• The gastric mill circuit in Homarus gammarus shares similarities with other decapod crustaceans.
• Parallel input pathways and internal network connectivity determine distinct motor program phenotypes (type I and type II).