Coordinated spinal locomotor network dynamics emerge from cell-type-specific connectivity patterns

Area of Science:

• Neuroscience
• Computational Biology
• Systems Biology

Background:

• Spinal locomotor circuitry generates coordinated movement (left-right alternation, segment-to-segment propagation, variable speed) without direct brain input.
• Existing models inadequately explain rhythmogenesis and recent findings on cell-type-specific connectivity and speed-selective interneurons.

Purpose of the Study:

• To develop and analyze a hierarchy of computational models for spinal locomotor networks.
• To investigate the network mechanisms underlying rhythmogenesis and variable-speed control in locomotion.

Main Methods:

• Developed a series of increasingly detailed computational models of the spinal locomotor network.
• Focused on inhibition-dominated networks with connectivity based on intersegmental phase relationships.
• Investigated the role of speed-selective interneuron subpopulations and excitatory connections.

Main Results:

• Coordinated locomotion emerges in inhibition-dominated networks with specific intersegmental connectivity.
• Variable-speed control is achieved by recruiting speed-selective interneuron subpopulations.
• Excitatory connections enhance peak frequency but can compromise smooth transitions, indicating a speed-control trade-off.

Conclusions:

• Network-level interactions are sufficient for generating coordinated, variable-speed locomotion.
• Provides new interpretations for the roles of intersegmental connectivity (excitatory and inhibitory).
• Identifies a recruitment-based mechanism for speed control in spinal locomotor networks.