Functional Recovery of a Locomotor Network after Injury: Plasticity beyond the Central Nervous System

Area of Science:

• Neuroscience
• Animal Locomotion
• Regenerative Medicine

Background:

• Animals rely on descending brain signals for locomotion.
• Locomotor function can recover after injury without central reconnection.
• Leech crawling recovery after descending input loss is previously established.

Purpose of the Study:

• Investigate mechanisms of locomotion recovery in leeches.
• Determine if central pattern generators (CPGs) alone coordinate crawling.
• Assess the role of the peripheral nervous system in coordinating recovery.

Main Methods:

• Activated isolated leech ganglia CPGs with dopamine.
• Recorded fictive crawling in dorsal-longitudinal-excitor motoneuron (DE-3).
• Removed peripheral afferent information in transected leeches.
• Traced peripheral nerve fiber regrowth using Neurobiotin.

Main Results:

• Activated CPGs produced bursting but lacked crawl-specific intersegmental coordination.
• Blocking peripheral afferent input significantly delayed or prevented crawling.
• Peripheral nerve fiber regrowth strongly correlated with crawl recovery.

Conclusions:

• Central pattern generators alone are insufficient for coordinating leech crawling.
• Peripheral nervous system afferent information is essential for organizing crawl coordination during recovery.
• Recovery of locomotion after injury involves a shift in coordination dependence to peripheral inputs.