An oscillatory neuronal circuit generating a locomotory rhythm

Area of Science:

• Neuroscience
• Animal Behavior
• Biophysics

Background:

• The neural control of locomotion is complex.
• Leech swimming involves coordinated body waves.
• Segmental ganglia in the ventral nerve cord coordinate movement.

Purpose of the Study:

• To identify the neural circuit responsible for generating leech swimming.
• To analyze the network properties of identified interneurons.
• To understand the role of synaptic connections in rhythmic motor output.

Main Methods:

• Identification of interneurons in the leech ventral nerve cord.
• Theoretical analysis of synaptic connections.
• Electronic analog modeling of neural networks.

Main Results:

• A quartet of interconnected interneurons was identified on each side of the segmental ganglia.
• These interneurons exhibit periodic activity that appears to generate the body wave.
• Analysis confirmed an oscillatory network with appropriate phase relations for swimming.

Conclusions:

• The identified interneuron network is the likely generator of the leech's swimming rhythm.
• Synaptic connections within and between ganglia are critical for network oscillation.
• This provides a model for understanding rhythmic motor pattern generation in other species.