Coordination in the crayfish swimmeret system: differential excitation causes changes in intersegmental phase

Area of Science:

• Neuroscience
• Animal Behavior

Background:

• The swimmeret system in crustaceans provides a model for studying neural circuit coordination.
• Understanding how neural circuits generate coordinated motor patterns is crucial for neuroscience.

Purpose of the Study:

• To investigate the role of excitation gradients in coordinating neural activity within the swimmeret system.
• To differentiate between proposed models of intersegmental coordination.

Main Methods:

• Isolated abdominal nerve cords were treated with cholinergic agonists (pilocarpine, carbachol) to create excitation gradients.
• Extracellular electrodes monitored neural activity in segments innervating swimmerets.
• The effects of stimulating different ganglia on motor pattern period and phase were analyzed.

Main Results:

• Cholinergic agonists elicited coordinated motor patterns from the entire system, even in untreated ganglia.
• Pattern period decreased with an increasing number of excited ganglia.
• Selective excitation of anterior or posterior ganglia altered intersegmental phase relationships.

Conclusions:

• Results support an asymmetric-coupling model for the swimmeret system's intersegmental coordinating circuit.
• The findings contradict an excitability-gradient model.
• Excitation gradients play a significant role in shaping coordinated motor output.